Recently a project I was working on called for a complex filter that was needed for selecting specific elements from a large data set. Looking at various methods of doing this, none provided a simple method to do so. First I wrote out my own Predicate<T> that was ugly with all of the if’s and flags necessary to implement it.
What I needed was something similar to a Hibernate query, that I could build out with a series of and’s, or’s, not’s, and a few other checks. I thought surely someone had created this. However, after much Googling I could find nothing. If someone out there knows of something please let me know.
I decided this was something worth creating. I decided it was something worth building.
QueryFilter Interface
First thing was to define an interface that would be used by all of the checks.
package name.mymiller.query;
/**
* Base filter for queries
*/
public interface QueryFilter<T> {
/**
* Must return true in order for this filter to agree to inclusion.
* @param object Object the filter should check
* @return Double indicating 0 if not to include, or Double > 0 indicating weight of matching
*/
Double process(T object);
}QueryFilter<T> would define the single class that would be called to check Query. So a simple 0.0 returned if it should not be included and a return > 0.0 if it should be included. Why did I make this a double? Sorting, putting this to use, I determined that it made sense to allow it to return a weight. This would allow me to sort the items based on weight. The higher the matching of the query the higher the item should be on the list.
Now you ask why wouldn’t the weight be all the same? Simple, a query that has an Or, can match any set of objects, as long as it matches one of the sub checks. Which should appear first in a list, an item that matches All of the checks, or one of the checks? The more checks the you match the higher on the sort you should appear.
Let’s talk QueryFilter’s
So we have our interface that is going to be required for our QueryFilters, however their behavior we still have several things we should take advantage of in their implementations.
First thing is we should have a default weight on the QueryFilter. This default weight should be consistent across all QueryFilter’s. I will be using 0.1 as my default weight. Next there should be a way to change the default weight for each filter. Certain checks maybe more valuable than others.
Next the QueryFilter should be able to run the check against the object itself, or allow the use of a Getter to check against a property on that object.
You may have an object that represents a person. You have a name and age of that person on the object. Your Query to look for anyone with a name that contains “Bob” or “Robert” in it, and older than 35. You would use a Getter to those properties of the object, and you may give the “Robert” a higher weight so they would appear first in the sorted list.
You will see I created far more QueryFilter’s than what I initially set out to create. Thoughts and little differences showed several more would be needed.
AbstractQuery
The AbstractQuery is for tracking and storing the weight. No sense to implement this on everything.
/**
*
* @param <T>
*/
public abstract class AbstractQuery<T> implements QueryFilter<T> {
/**
*
*/
private Double weight;
/**
*
* @param weight
*/
public AbstractQuery(Double weight) {
this.weight = weight;
}
/**
*
* @return
*/
public Double getWeight() {
return weight;
}
}And QueryFilter
The And QueryFilter is a simple filter that takes multiple QueryFilter’s and each of them must return a value > 0 in order for the And to return a value.
/**
* Used to "And" a list of queries together. All filters must pass in order for this one to return true.
* Any Filter added that is "null" will be ignored.
*/
public static class And<T> implements QueryFilter<T> {
/**
* LIst of QueryFilters to check if all pass
*/
private final List<QueryFilter<T>> list;
/**
* Generate an And Filter with a list.
*
* @param list List of QueryFilter to require to be true.
*/
public And(List<QueryFilter<T>> list) {
this.list = list;
}
/**
* Variable list of filters to require to be true.
*
* @param filters Variable argument list of filters to process
*/
public And(QueryFilter<T>... filters) {
this.list = Arrays.asList(filters);
}
/**
* Create a blank And Filter
*/
public And() {
this.list = new ArrayList<>();
}
/**
* Add a QueryFilter to the AndFilter
*
* @param queryFilter QueryFilter to add
* @return boolean indicating if successfully added
*/
public boolean add(QueryFilter<T> queryFilter) {
return list.add(queryFilter);
}
@Override
public Double process(T object) {
if (this.list.parallelStream().filter(Objects::nonNull).allMatch(filter -> filter.process(object) > 0)) {
return this.list.parallelStream().filter(Objects::nonNull).mapToDouble(filter -> filter.process(object)).sum();
}
return 0D;
}
}Several constructors are provided for entering in additional QueryFilter’s by passing in a List, Array, of making use of the add() method to add additional QueryFilter’s. No weight is set here, because the And takes the sum of all the weights it receives.
Between QueryFilter
This QueryFilter checks to see if the value is between two values. Not Between or Equal to, this must be between the values. It makes use of the And QueryFilter and the LessThan / GreaterThan that we discuss soon.
/**
* QueryFilter to check if a value is between a low and max. Must be a comparable type
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
*/
public static class Between<T, R> implements QueryFilter<T> {
/**
* Internal Add, to use in combination with a GreaterThan and LessThan
*/
private And and;
/**
* Check if value falls between two values
* @param low low value
* @param max max value
*/
public Between(T low, T max) {
this.and = new And(new LessThan(max), new GreaterThan(low));
}
/**
* Check if value falls between two values on the value of a getter
* @param getter the function used to extract the Comparable sort key
* @param low low value
* @param max max value
*/
public Between(Function<T, R> getter, T low, T max) {
this.and = new And(new LessThan(getter, max), new GreaterThan(getter, low));
}
/**
* Must return true in order for this filter to agree to inclusion.
*
* @param object Object the filter should check
* @return Boolean indicating if agree to inclusion.
*/
@Override
public Double process(T object) {
return and.process(object);
}
}No need for a full implementation, we instead take advantage of the other QueryFilter’s we have in place, to keep this one simple.
BetweenOrEqual QueryFilter
Just like the Between QueryFilter, except this checks to see if they match low/max as well.
/**
*QueryFilter to check if a value is between a low and max or equal. Must be a comparable type
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
*/
public static class BetweenOrEqual<T, R> implements QueryFilter<T> {
/**
* Internal Or filter
*/
private Or or;
/**
* Check if value falls between min/max or equal
* @param low
* @param max
*/
public BetweenOrEqual(T low, T max) {
this.or = new Or(new And(new LessThan(max), new GreaterThan(low)), new Match(low), new Match(max));
}
/**
* Check if value falls between min/max or equal on the value of the getter
* @param getter the function used to extract the Comparable sort key
* @param low
* @param max
*/
public BetweenOrEqual(Function<T, R> getter, T low, T max) {
this.or = new Or(new And(new LessThan(getter, max), new GreaterThan(getter, low)), new Match(getter, low), new Match(getter, max));
}
/**
* Must return true in order for this filter to agree to inclusion.
*
* @param object Object the filter should check
* @return Boolean indicating if agree to inclusion.
*/
@Override
public Double process(T object) {
return or.process(object);
}
}We are able to keep the implementation simple, by making use of other QueryFilter’s.
Contains QueryFilter
This one works by checking if a String property contains a substring to match the given string. It also has one additional change, a multiplier. This multiplier is used if we get an exact match. The multiplier is applied to the weight. An item that is an exact match will be given increased weight over an object that just contains the string.
/**
* Check if the values associated with key contains the text in the value.
*/
public static class Contains<T> extends AbstractQuery<T> {
/**
* Value to see if is in contains
*/
private final String value;
/**
* Value to muliple weight if an exact match
*/
private final Integer multiplier;
/**
* Getter function
*/
private Function<T, String> getter;
/**
* Constructor to check if value is contained in the object
* @param value the value to compe on
*/
public Contains(String value) {
super(1D);
this.multiplier = 2;
this.value = value;
this.getter = null;
}
/**
* Constructor to check if value is contained in the getter
* @param value the value to compe on
* @param getter the function used to extract the Comparable sort key
*/
public Contains(String value, Function<T, String> getter) {
super(1D);
this.multiplier = 2;
this.value = value;
this.getter = getter;
}
/**
* Constructor to check if value is contained in the object
* @param value the value to compe on
* @param weigth the weight this should return if QueryFilter return matches.
* @param multiplier In the case of an exact match, this is applied to the weight
*/
public Contains(String value, Double weigth, Integer multiplier) {
super(weigth);
this.multiplier = multiplier;
this.value = value;
this.getter = null;
}
/**
* Constructor to check if value is contained in the object on the getter
* @param value the value to compe on
* @param getter the function used to extract the Comparable sort key
* @param weight the weight this should return if QueryFilter return matches.
* @param multiplier In the case of an exact match, this is applied to the weight
*/
public Contains(String value, Function<T, String> getter, Double weight, Integer multiplier) {
super(weight);
this.multiplier = multiplier;
this.value = value;
this.getter = getter;
}
/**
* Must return true in order for this filter to agree to inclusion.
*
* @param object String the filter should check
* @return Boolean indicating if agree to inclusion.
*/
@Override
public Double process(T object) {
if (object != null && value != null) {
if (getter == null) {
if (object.toString().contains(value)) {
if (object.toString().equals(value)) {
return this.getWeight() * multiplier;
}
return this.getWeight();
}
} else if (getter != null) {
String content = this.getter.apply(object);
if (content != null) {
if (content.contains(value)) ;
{
if (content.equals(value)) {
return this.getWeight() * multiplier;
}
return this.getWeight();
}
}
}
}
if (object == null && value == null) {
return this.getWeight();
}
return 0D;
}
}GreaterThan QueryFilter
A queryfilter that checks if the value is > not >= just >. The value must be a comparable.
/**
* Check if the value is greater than the indicate value. Object must be comparable.
* @param <T> Type of object to filter. Must be of Comparable Type
* @param <R> Type returned from the Getter. Must be of Comparable Type
*/
public static class GreaterThan<T, R> extends AbstractQuery<T> {
/**
* Getter function
*/
private Function<T, R> getter;
/**
* Value to compare against
*/
private T value;
/**
* Constructor to check if the object is greater than
* @param value the value to compare on.
*/
public GreaterThan(T value) {
super(.1D);
if (value != null) {
ObjectUtils.throwIfNotInstance(Comparable.class, value, "Object must be Comparable.");
}
this.value = value;
}
/**
* Constructor to check if the object is greather than, with the specified weight.
* @param value the value to compare on
* @param weight the weight this should return if QueryFilter return matches.
*/
public GreaterThan(T value, Double weight) {
super(weight);
if (value != null) {
ObjectUtils.throwIfNotInstance(Comparable.class, value, "Object must be Comparable.");
}
this.value = value;
}
/**
* Constructor to use a Getter to compare aginst the value.
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
*/
public GreaterThan(Function<T, R> getter, T value) {
super(.1D);
if (value != null) {
ObjectUtils.throwIfNotInstance(Comparable.class, value, "Object must be Comparable.");
}
this.getter = getter;
this.value = value;
}
/**
* Constructor use a getter to compare against the value, and use the spedified weight.
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
*/
public GreaterThan(Function<T, R> getter, T value, Double weight) {
super(weight);
if (value != null) {
ObjectUtils.throwIfNotInstance(Comparable.class, value, "Object must be Comparable.");
}
this.getter = getter;
this.value = value;
}
/**
* Must return true in order for this filter to agree to inclusion.
*
* @param object Object the filter should check
* @return Boolean indicating if agree to inclusion.
*/
@Override
public Double process(T object) {
if (object != null && this.value != null) {
if (this.getter == null) {
ObjectUtils.throwIfNotInstance(Comparable.class, object, "Object must be Comparable.");
if (((Comparable<T>) object).compareTo(this.value) > 0) {
return this.getWeight();
}
} else {
Object obj = this.getter.apply(object);
ObjectUtils.throwIfNotInstance(Comparable.class, obj, "Value from getter must be Comparable.");
if (((Comparable<T>) obj).compareTo(this.value) > 0) {
return this.getWeight();
}
}
}
return 0D;
}
}This will throw an IllegalArgumentException if the value is not a Comparable.
IsEmpty QueryFilter
QueryFilter to check a value that is a string if it is empty. In this case it returns > 0 if the string is empty.
/**
* Check if the value of the string is empty. Null will return 0.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
*/
public static class IsEmpty<T, R> extends AbstractQuery<T> {
/**
* Getter Function
*/
private Function<T, R> getter;
/**
* Constructor with default weight
*/
public IsEmpty() {
super(.1D);
}
/**
* Constructor with specified weight.
* @param weight the weight this should return if QueryFilter return matches.
*/
public IsEmpty(Double weight) {
super(weight);
}
/**
* Constructor to use Getter
* @param getter the function used to extract the Comparable sort key
*/
public IsEmpty(Function<T, R> getter) {
super(.1D);
this.getter = getter;
}
/**
* Constructor to use Getter and specified Weigth.
* @param getter the function used to extract the Comparable sort key
* @param weight the weight this should return if QueryFilter return matches.
*/
public IsEmpty(Function<T, R> getter, Double weight) {
super(weight);
this.getter = getter;
}
/**
* Must return true in order for this filter to agree to inclusion.
*
* @param object Object the filter should check
* @return Double indicating 0 if not include, of Double > 0 indicating weight.
*/
@Override
public Double process(T object) {
if (object != null) {
if (this.getter != null) {
Object obj = this.getter.apply(object);
ObjectUtils.throwIfNotInstance(String.class, obj, "Value from getter must be of type String");
if (object.toString().isEmpty()) {
return this.getWeight();
}
} else {
ObjectUtils.throwIfNotInstance(String.class, object, "Object must be of type String");
if (object.toString().isEmpty()) {
return this.getWeight();
}
}
}
return 0D;
}
}This will throw an IllegalArgumentException if the value is not a String.
IsNull QueryFilter
Simple QueryFilter that checks if the value is Null, if it is null then it return > 0.
/**
* Query Filter to check for Null
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
*/
public static class IsNull<T, R> extends AbstractQuery<T> {
/**
* Getter Function
*/
private Function<T, R> getter;
/**
* Constructor for with default weight.
*/
public IsNull() {
super(.1D);
}
/**
* Constructor with specified weight.
* @param weight the weight this should return if QueryFilter return matches.
*/
public IsNull(Double weight) {
super(weight);
}
/**
* Constructor with Getter
* @param getter the function used to extract the Comparable sort key
*/
public IsNull(Function<T, R> getter) {
super(.1D);
this.getter = getter;
}
/**
* Constructor with Getter and Weight
* @param getter the function used to extract the Comparable sort key
* @param weight the weight this should return if QueryFilter return matches.
*/
public IsNull(Function<T, R> getter, Double weight) {
super(weight);
this.getter = getter;
}
/**
* Must return true in order for this filter to agree to inclusion.
*
* @param object Object the filter should check
* @return Double indicating 0 if not include, of Double > 0 indicating weight.
*/
@Override
public Double process(T object) {
if (this.getter != null) {
Object obj = this.getter.apply(object);
if (object == null) {
return this.getWeight();
}
} else if (object == null) {
return this.getWeight();
}
return 0D;
}
}LessThan QueryFilter
Just like the GreaterThan QueryFilter, this one checks if the value is less than the indicated value. It does not checks <= only <.
/**
* Query Filter to check if value is less than indicate value.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
*/
public static class LessThan<T, R> extends AbstractQuery<T> {
/**
* Value to compare
*/
private T value;
/**
* Getter Function
*/
private Function<T, R> getter;
/**
* Constructor with value
* @param value the value to compe on
*/
public LessThan(T value) {
super(.1D);
if (value != null) {
ObjectUtils.throwIfNotInstance(Comparable.class, value, "Object must be Comparable.");
}
this.value = value;
}
/**
* Constructor with value and weight.
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
*/
public LessThan(T value, Double weight) {
super(weight);
if (value != null) {
ObjectUtils.throwIfNotInstance(Comparable.class, value, "Object must be Comparable.");
}
this.value = value;
}
/**
* Constructor with Getter and Valued
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
*/
public LessThan(Function<T, R> getter, T value) {
super(.1D);
if (value != null) {
ObjectUtils.throwIfNotInstance(Comparable.class, value, "Object must be Comparable.");
}
this.getter = getter;
this.value = value;
}
/**
* Constructor with Getter, Value and Weight
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
*/
public LessThan(Function<T, R> getter, T value, Double weight) {
super(weight);
if (value != null) {
ObjectUtils.throwIfNotInstance(Comparable.class, value, "Object must be Comparable.");
}
this.getter = getter;
this.value = value;
}
/**
* Must return true in order for this filter to agree to inclusion.
*
* @param object Object the filter should check
* @return Boolean indicating if agree to inclusion.
*/
@Override
public Double process(T object) {
if (object != null && this.value != null) {
if (this.getter == null) {
ObjectUtils.throwIfNotInstance(Comparable.class, object, "Object must be Comparable.");
if (((Comparable<T>) object).compareTo(this.value) < 0) {
return this.getWeight();
}
} else {
Object obj = this.getter.apply(object);
ObjectUtils.throwIfNotInstance(Comparable.class, obj, "Value from getter must be Comparable.");
if (((Comparable<T>) obj).compareTo(this.value) < 0) {
return this.getWeight();
}
}
}
return 0D;
}
}This will throw an IllegalArgumentException if the value is not a Comparable.
Match QueryFilter
This QueryFilter should be called Equals, however because of Object::equals(), I could not add it to the Query object itself as a static shortcut method.
/**
* Compares an object to see if they are Equal.
*/
public static class Match<T, R> extends AbstractQuery<T> {
/**
* Value to compare
*/
private final T value;
/**
* Getter Function
*/
private Function<T, R> getter;
/**
* Constrctor with value to compare.
* @param value the value to compe on
*/
public Match(T value) {
super(1D);
if (value == null) {
throw new NullPointerException("value may not be null");
}
this.value = value;
this.getter = null;
}
/**
* Constructor with Getter and value to compare.
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
*/
public Match(Function<T, R> getter, T value) {
super(1D);
this.value = value;
this.getter = getter;
}
/**
* Constructor with value to compare and weight.
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
*/
public Match(T value, Double weight) {
super(weight);
if (value == null) {
throw new NullPointerException("value may not be null");
}
this.value = value;
this.getter = null;
}
/**
* Constructor with getter, value to compare and weight.
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
*/
public Match(Function<T, R> getter, T value, Double weight) {
super(weight);
this.value = value;
this.getter = getter;
}
@Override
public Double process(T object) {
if (getter == null) {
if (value.equals(object)) {
return this.getWeight();
}
} else if (value.equals(this.getter.apply(object))) {
return this.getWeight();
}
return 0D;
}
}There is no multiplier here like Contains QueryFilter. This is expected to be a 100% or not all. This makes use of the Object::Equals so this must be implemented correctly on your type.
Not QueryFilter
Simply flips the value returned by the specified QueryFilter. If the specified QueryFilter return > 0, this will return 0, if it returns 0 it returns the indicated weight.
/**
* Used to flip the value of a filter.
*/
public static class Not<T> extends AbstractQuery<T> {
/**
* Filter to flip the value on.
*/
private final QueryFilter<T> filter;
/**
* Create a NotFilter to flip the value of a filter
*
* @param filter filter to flip the value on.
*/
public Not(QueryFilter<T> filter) {
super(.1D);
if (filter == null) {
throw new NullPointerException("Filter may not be null");
}
this.filter = filter;
}
/**
* Creatre NotFilter to flip the value on, with specified weight.
* @param filter Filter to flip value on.
* @param weight the weight this should return if QueryFilter return matches.
*/
public Not(QueryFilter<T> filter, Double weight) {
super(weight);
if (filter == null) {
throw new NullPointerException("Filter may not be null");
}
this.filter = filter;
}
@Override
public Double process(T object) {
if (this.filter.process(object) == 0D) {
return this.getWeight();
}
return 0D;
}
}NotEmpty QueryFilter
A simple QueryFilter that uses the Not and IsEmpty to create a NotEmpty. A shortcut QueryFilter for use, and one that is often missing. I find myself needing a notEmpty() far more often than I need an isEmpty().
/**
* Query Filter to check if string is not empty
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
*/
public static class NotEmpty<T, R> implements QueryFilter<T> {
/**
* Not filter to use internally to flip IsEmpty.
*/
private Not not;
/**
* Constructor with default weight.
*/
public NotEmpty() {
this.not = new Not(new IsEmpty());
}
/**
* Constructor with specified weight.
* @param weight the weight this should return if QueryFilter return matches.
*/
public NotEmpty(Double weight) {
this.not = new Not(new IsEmpty(weight));
}
/**
* Constructor with getter
* @param getter the function used to extract the Comparable sort key
*/
public NotEmpty(Function<T, R> getter) {
this.not = new Not(new IsEmpty(getter));
}
/**
* Constructor with getter and weight specified
* @param getter the function used to extract the Comparable sort key
* @param weight the weight this should return if QueryFilter return matches.
*/
public NotEmpty(Function<T, R> getter, Double weight) {
this.not = new Not(new IsEmpty(getter, weight));
}
/**
* Must return true in order for this filter to agree to inclusion.
*
* @param object Object the filter should check
* @return Double indicating 0 if not include, of Double > 0 indicating weight.
*/
@Override
public Double process(T object) {
return this.not.process(object);
}
}NotNull QueryFilter
A simple QueryFilter that uses the Not and IsNull to create a NotNull. A shortcut QueryFilter for use, and one that is often missing. I find myself needing a notNull() far more often than I need an isEmpty().
/**
* Query Filter to check if value is not null
* @param <T> Type of object to filter
* @param <R> Type returned from the Gettervvv
*/
public static class NotNull<T, R> implements QueryFilter<T> {
/**
* Not query filter to flip
*/
private Not not;
/**
* Constructor with default weight.
*/
public NotNull() {
this.not = new Not(new IsNull());
}
/**
*
* @param weight the weight this should return if QueryFilter return matches.
*/
public NotNull(Double weight) {
this.not = new Not(new IsNull(weight));
}
/**
*
* @param getter the function used to extract the Comparable sort key
*/
public NotNull(Function<T, R> getter) {
this.not = new Not(new IsNull(getter));
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param weight the weight this should return if QueryFilter return matches.
*/
public NotNull(Function<T, R> getter, Double weight) {
this.not = new Not(new IsNull(getter, weight));
}
/**
* Must return true in order for this filter to agree to inclusion.
*
* @param object Object the filter should check
* @return Double indicating 0 if not include, of Double > 0 indicating weight.
*/
@Override
public Double process(T object) {
return this.not.process(object);
}
}Or QueryFilter
The Or QueryFilter is a simple filter that takes multiple QueryFilter’s and one of them must return a value > 0 in order for the Or to return a value.
/**
* Used to "Or" a list of queries together. Any filter returning true for this one to return true.
* Any Filter added that is "null" will be ignored.
*/
public static class Or<T> implements QueryFilter<T> {
private final List<QueryFilter<T>> list;
/**
* Generate an Or Filter with a list.
*
* @param list List of QueryFilter to require to be true.
*/
public Or(List<QueryFilter<T>> list) {
this.list = list;
}
/**
* Variable list of filters to check if one is true.
*
* @param filters Variable argument list of filters to process
*/
public Or(QueryFilter<T>... filters) {
this.list = Arrays.asList(filters);
}
/**
* Create a blank Or Filter
*/
public Or() {
this.list = new ArrayList<>();
}
/**
* Add a QueryFilter to the OrFilter
*
* @param queryFilter QueryFilter to add
* @return boolean indicating if successfully added
*/
public boolean add(QueryFilter<T> queryFilter) {
return list.add(queryFilter);
}
@Override
public Double process(T object) {
return this.list.parallelStream().filter(Objects::nonNull).map(filter -> filter.process(object)).filter(value -> value > 0).mapToDouble(value -> value).sum();
}
}Xor QueryFilter
The Xor QueryFilter is a simple filter that takes multiple QueryFilter’s and only one can return a value > 0 in order for the Xor to return a value.
/**
* Used to "Xor a list of queries together. Only one filter may return true for this one to return true.
* Any Filter added that is "null" will be ignored.
*/
public static class Xor<T> implements QueryFilter<T> {
private final List<QueryFilter<T>> list;
/**
* Generate an Or Filter with a list.
*
* @param list List of QueryFilter to process.
*/
public Xor(List<QueryFilter<T>> list) {
this.list = list;
}
/**
* Variable list of filters to check if one is true.
*
* @param filters Variable argument list of filters to process
*/
public Xor(QueryFilter<T>... filters) {
this.list = Arrays.asList(filters);
}
/**
* Create a blank Or Filter
*/
public Xor() {
this.list = new ArrayList<>();
}
/**
* Add a QueryFilter to the OrFilter
*
* @param queryFilter QueryFilter to add
* @return boolean indicating if successfully added
*/
public boolean add(QueryFilter<T> queryFilter) {
return list.add(queryFilter);
}
@Override
public Double process(T object) {
List<Double> values = this.list.parallelStream().filter(Objects::nonNull).map(filter -> filter.process(object)).collect(Collectors.toList());
values = values.stream().filter(value -> value != 0D).collect(Collectors.toList());
if (values.size() == 1) {
return values.get(0);
}
return 0D;
}
}Query Class and shortcut methods
I’m always looking for shortcuts in programming. Redundant code is just twice the amount of work. Therefore I look for ways to reduce any redundancy that I can. To that extent I created a Query class, with conveinence methods on it to build out a complex query easier. There is nothing fancy here.
/**
* Wraps a number of queries in an And filter. All queries must return a weight > 0 in order of this to pass.
* @param filters Array of filters to be wrapped in the And.
* @param <T> Type of object to filter
* @return And QueryFilter with the filters added to it
*/
public static <T> And<T> and(QueryFilter<T>... filters) {
return new And<>(filters);
}
/**
* Wraps a number of queries in an And filter. All queries must return a weight > 0 in order of this to pass.
* @param list List of QueryFilters for this And.
* @param <T> Type of object to filter
* @return And QueryFilter with the list of filters added to it
*/
public static <T> And<T> and(List<QueryFilter<T>> list) {
return new And<>(list);
}
/**
* Wraps a number of queries in an And filter. All queries must return a weight > 0 in order of this to pass.
* @param <T> Type of object to filter
* @return And QueryFilter ready to add queries to.
*/
public static <T> And<T> and() {
return new And<>();
}
/**
* Creates a QueryFilter that will pass the filter if the object is between low and max.
* @param low the low value to compare on.
* @param max the hight value to compare on.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return Between QueryFilter to check if the value is between low/max
*/
public static <T, R> Between<T, R> between(T low, T max) {
return new Between<>(low, max);
}
/**
* Creates a QueryFilter that will pass the filter if the object is between low and max.
* @param getter the function used to extract the Comparable sort key
* @param low the low value to compare on.
* @param max the hight value to compare on.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return Between QueryFilter to check if the value is between low/max
*/
public static <T, R> Between<T, R> between(Function<T, R> getter, T low, T max) {
return new Between<>(getter, low, max);
}
/**
*
* @param low the low value to compare on.
* @param max the hight value to compare on.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return BetweenOrEuals QueryFilter to check if the value is between low/max or equal
*/
public static <T, R> BetweenOrEqual<T, R> betweenOrEqual(T low, T max) {
return new BetweenOrEqual<>(low, max);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param low the low value to compare on.
* @param max the hight value to compare on.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return BetweenOrEuals QueryFilter to check if the value is between low/max or equal
*/
public static <T, R> BetweenOrEqual<T, R> betweenOrEqual(Function<T, R> getter, T low, T max) {
return new BetweenOrEqual<>(getter, low, max);
}
/**
*
* @param value the value to compe on the value to compare on.
* @param <T> Type of object to filter
* @return Contains QueryFilter to check if the object contains the value.
*/
public static <T> Contains<T> contains(String value) {
return new Contains<T>(value);
}
/**
*
* @param value the value to compe on
* @param getter the function used to extract the Comparable sort key
* @param <T> Type of object to filter
* @return Contains QueryFilter to check if the object contains the value.
*/
public static <T> Contains<T> contains(String value, Function<T, String> getter) {
return new Contains<T>(value, getter);
}
/**
*
* @param value the value to compe on
* @param weigth the weight this should return if QueryFilter return matches.
* @param multiplier In the case of an exact match, this is applied to the weight
* @param <T> Type of object to filter
* @return Contains QueryFilter to check if the object contains the value.
*/
public static <T> Contains<T> contains(String value, Double weigth, Integer multiplier) {
return new Contains<T>(value, weigth, multiplier);
}
/**
*
* @param value the value to compe on
* @param getter the function used to extract the Comparable sort key
* @param weight the weight this should return if QueryFilter return matches.
* @param multiplier In the case of an exact match, this is applied to the weight
* @param <T> Type of object to filter
* @return Contains QueryFilter to check if the object contains the value.
*/
public static <T> Contains<T> contains(String value, Function<T, String> getter, Double weight, Integer multiplier) {
return new Contains<T>(value, getter, weight, multiplier);
}
/**
*
* @param value the value to compe on
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return Match QueryFilter to check if the object equalss the value.
*/
public static <T, R> Match<T, R> match(T value) {
return new Match<>(value);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return Match QueryFilter to check if the object equalss the value.
*/
public static <T, R> Match<T, R> match(Function<T, R> getter, T value) {
return new Match<>(getter, value);
}
/**
*
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return Match QueryFilter to check if the object equalss the value.
*/
public static <T, R> Match<T, R> match(T value, Double weight) {
return new Match<>(value, weight);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return Match QueryFilter to check if the object equalss the value.
*/
public static <T, R> Match<T, R> match(Function<T, R> getter, T value, Double weight) {
return new Match<>(getter, value, weight);
}
/**
*
* @param value the value to compe on
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return GreaterThan QueryFilter to check if the object is greater than the value when compared.
*/
public static <T, R> GreaterThan<T, R> greaterThan(T value) {
return new GreaterThan<>(value);
}
/**
*
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return GreaterThan QueryFilter to check if the object is greater than the value when compared.
*/
public static <T, R> GreaterThan<T, R> greaterThan(T value, Double weight) {
return new GreaterThan<>(value, weight);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return GreaterThan QueryFilter to check if the object is greater than the value when compared.
*/
public static <T, R> GreaterThan<T, R> greaterThan(Function<T, R> getter, T value) {
return new GreaterThan<>(getter, value);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return GreaterThan QueryFilter to check if the object is greater than the value when compared.
*/
public static <T, R> GreaterThan<T, R> greaterThan(Function<T, R> getter, T value, Double weight) {
return new GreaterThan<>(getter, value, weight);
}
/**
*
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return IsEmpty QueryFilter to check if the object is empty
*/
public static <T, R> IsEmpty<T, R> isEmpty() {
return new IsEmpty<>();
}
/**
*
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return IsEmpty QueryFilter to check if the object is empty
*/
public static <T, R> IsEmpty<T, R> isEmpty(Double weight) {
return new IsEmpty<>(weight);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return IsEmpty QueryFilter to check if the object is empty
*/
public static <T, R> IsEmpty<T, R> isEmpty(Function<T, R> getter) {
return new IsEmpty<>(getter);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return IsEmpty QueryFilter to check if the object is empty
*/
public static <T, R> IsEmpty<T, R> isEmpty(Function<T, R> getter, Double weight) {
return new IsEmpty<>(getter, weight);
}
/**
*
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return IsNull QueryFilter to check if the object is null
*/
public static <T, R> IsNull<T, R> isNull() {
return new IsNull<>();
}
/**
*
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return IsNull QueryFilter to check if the object is null
*/
public static <T, R> IsNull<T, R> isNull(Double weight) {
return new IsNull<>(weight);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return IsNull QueryFilter to check if the object is null
*/
public static <T, R> IsNull<T, R> isNull(Function<T, R> getter) {
return new IsNull<>(getter);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return IsNull QueryFilter to check if the object is null
*/
public static <T, R> IsNull<T, R> isNull(Function<T, R> getter, Double weight) {
return new IsNull<>(getter, weight);
}
/**
*
* @param value the value to compe on
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return LessThan QueryFilter to check if the object is less than the value when compared.
*/
public static <T, R> LessThan<T, R> lessThan(T value) {
return new LessThan<>(value);
}
/**
*
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return LessThan QueryFilter to check if the object is less than the value when compared.
*/
public static <T, R> LessThan<T, R> lessThan(T value, Double weight) {
return new LessThan<>(value, weight);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return LessThan QueryFilter to check if the object is less than the value when compared.
*/
public static <T, R> LessThan<T, R> lessThan(Function<T, R> getter, T value) {
return new LessThan<>(getter, value);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param value the value to compe on
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return LessThan QueryFilter to check if the object is less than the value when compared.
*/
public static <T, R> LessThan<T, R> lessThan(Function<T, R> getter, T value, Double weight) {
return new LessThan<>(getter, value, weight);
}
/**
*
* @param filter QueryFilter to flip the value on
* @param <T> Type of object to filter
* @return Not QueryFilter flips the value of QueryFilter
*/
public static <T> Not<T> not(QueryFilter<T> filter) {
return new Not<>(filter);
}
/**
*
* @param filter QueryFilter to flip the value on
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @return Not QueryFilter flips the value of QueryFilter
*/
public static <T> Not<T> not(QueryFilter<T> filter, Double weight) {
return new Not<>(filter, weight);
}
/**
*
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return NotEmpty QueryFilter to check if the object is not empty
*/
public static <T, R> NotEmpty<T, R> notEmpty() {
return new NotEmpty<>();
}
/**
*
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return NotEmpty QueryFilter to check if the object is not empty
*/
public static <T, R> NotEmpty<T, R> notEmpty(Double weight) {
return new NotEmpty<>(weight);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return NotEmpty QueryFilter to check if the object is not empty
*/
public static <T, R> NotEmpty<T, R> notEmpty(Function<T, R> getter) {
return new NotEmpty<>(getter);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return NotEmpty QueryFilter to check if the object is not empty
*/
public static <T, R> NotEmpty<T, R> notEmpty(Function<T, R> getter, Double weight) {
return new NotEmpty<>(getter, weight);
}
/**
*
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return NotNull QueryFilter to check if the object is not null
*/
public static <T, R> NotNull<T, R> notNull() {
return new NotNull<>();
}
/**
*
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return NotNull QueryFilter to check if the object is not null
*/
public static <T, R> NotNull<T, R> notNull(Double weight) {
return new NotNull<>(weight);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return NotNull QueryFilter to check if the object is not null
*/
public static <T, R> NotNull<T, R> notNull(Function<T, R> getter) {
return new NotNull<>(getter);
}
/**
*
* @param getter the function used to extract the Comparable sort key
* @param weight the weight this should return if QueryFilter return matches.
* @param <T> Type of object to filter
* @param <R> Type returned from the Getter
* @return NotNull QueryFilter to check if the object is not null
*/
public static <T, R> NotNull<T, R> notNull(Function<T, R> getter, Double weight) {
return new NotNull<>(getter, weight);
}
/**
*
* @param list List of QueryFilters to include in the Or
* @param <T> Type of object to filter
* @return Or queryFilter to check if at least one QueryFilter in the Or is positive.
*/
public static <T> Or<T> or(List<QueryFilter<T>> list) {
return new Or<>(list);
}
/**
*
* @param filters Array of QueryFilters to include in the Or
* @param <T> Type of object to filter
* @return Or queryFilter to check if at least one QueryFilter in the Or is positive.
*/
public static <T> Or<T> or(QueryFilter<T>... filters) {
return new Or<>(filters);
}
/**
*
* @param <T> Type of object to filter
* @return Or queryFilter to check if at least one QueryFilter in the Or is positive.
*/
public static <T> Or<T> or() {
return new Or<>();
}
/**
*
* @param <T> Type of object to filter
* @return Or queryFilter to check if only one QueryFilter in the Or is positive.
*/
public static <T> Xor<T> xor() {
return new Xor<>();
}
/**
*
* @param list List of QueryFilters to include in the Xor
* @param <T> Type of object to filter
* @return Or queryFilter to check if only one QueryFilter in the Or is positive.
*/
public static <T> Xor<T> xor(List<QueryFilter<T>> list) {
return new Xor<>(list);
}
/**
*
* @param filters Array of QueryFilters to include in the Xor
* @param <T> Type of object to filter
* @return Or queryFilter to check if only one QueryFilter in the Or is positive.
*/
public static <T> Xor<T> xor(QueryFilter<T>... filters) {
return new Xor<>(filters);
}
This is for creating queries that are readable.
And and = new And(new Match(Person::getName,"Bob"),new Between(Person::getAge,35,55))or
And and = Query.and(Query.match(Person::getName,"Bob"),Query.between(Person::getAge,35,55));QueryFilterStream use in stream::filter
So we’ve created all of this code, but how do we use it? Well, it was designed for two places to be used. In a Stream::filter is the first place. For this, we created a QueryFilterStream that implements a Predicate.
/**
* QueryFilter Predicate to use in a filter method for determining whether to filter the item.
* @param <T> Type of object to filter
*/
public static class QueryFilterStream<T> implements Predicate<T> {
/**
* QueryFilter to use in the processing
*/
private QueryFilter<T> filter;
/**
* Constructor for creating the QueryFilter for filter processing
* @param filter QueryFilter to use for processing.
*/
public QueryFilterStream(QueryFilter<T> filter) {
this.filter = filter;
}
/**
* Evaluates this predicate on the given argument.
*
* @param t the input argument
* @return {@code true} if the input argument matches the predicate,
* otherwise {@code false}
*/
@Override
public boolean test(T t) {
if (filter.process(t) > 0D) {
return true;
}
return false;
}
}Simple method that will call the process() method on a QueryFilter and return true if the value returned is > 0, otherwise it returns false. Wrap you query as needed and pass into Query::filter method to generate this filter to use in Stream::filter
/**
* Given a QueryFilter to use, returns a Predicate suited for a Java Stream, or Pipeline filter() call.
*
* @param filter QueryFilter structure defining the query to perform
* @param <T> Type of data that will be passed in.
* @return Predicate suitable for a filter() call.
*/
public static <T> Predicate<T> filter(QueryFilter<T> filter) {
return new QueryFilterStream<>(filter);
}QueryComparator use in Stream::sorted
This was the whole point of creating this system with weights. Now we can use the weight to determine the sorting order. For ths I created the QueryComparator that implements a Comparator
/**
* Comparator that accepts a QueryFilter for processing weights to determine order.
* @param <T> Type of object in filter
*/
public static class QueryComparator<T> implements Comparator<T> {
/**
*
*/
private QueryFilter<T> filter;
/**
* Constructor taking in the QueryFilter to use for processing
* @param filter QueryFilter to use for processing.
*/
public QueryComparator(QueryFilter<T> filter) {
this.filter = filter;
}
/**
* Compares its two arguments for order. Returns a negative integer,
* zero, or a positive integer as the first argument is less than, equal
* to, or greater than the second.<p>
* <p>
* The implementor must ensure that {@code sgn(compare(x, y)) ==
* -sgn(compare(y, x))} for all {@code x} and {@code y}. (This
* implies that {@code compare(x, y)} must throw an exception if and only
* if {@code compare(y, x)} throws an exception.)<p>
* <p>
* The implementor must also ensure that the relation is transitive:
* {@code ((compare(x, y)>0) && (compare(y, z)>0))} implies
* {@code compare(x, z)>0}.<p>
* <p>
* Finally, the implementor must ensure that {@code compare(x, y)==0}
* implies that {@code sgn(compare(x, z))==sgn(compare(y, z))} for all
* {@code z}.<p>
* <p>
* It is generally the case, but <i>not</i> strictly required that
* {@code (compare(x, y)==0) == (x.equals(y))}. Generally speaking,
* any comparator that violates this condition should clearly indicate
* this fact. The recommended language is "Note: this comparator
* imposes orderings that are inconsistent with equals."<p>
* <p>
* In the foregoing description, the notation
* {@code sgn(}<i>expression</i>{@code )} designates the mathematical
* <i>signum</i> function, which is defined to return one of {@code -1},
* {@code 0}, or {@code 1} according to whether the value of
* <i>expression</i> is negative, zero, or positive, respectively.
*
* @param o1 the first object to be compared.
* @param o2 the second object to be compared.
* @return a negative integer, zero, or a positive integer as the
* first argument is less than, equal to, or greater than the
* second.
* @throws NullPointerException if an argument is null and this
* comparator does not permit null arguments
* @throws ClassCastException if the arguments' types prevent them from
* being compared by this comparator.
*/
@Override
public int compare(T o1, T o2) {
Double value1 = this.filter.process(o1);
Double value2 = this.filter.process(o2);
return value1.compareTo(value2);
}
}Simple method that will call the process() method for two objects on the QueryFilter and compare the results. Wrap you query as needed and pass into Query::comparator method to generate this filter to use in Stream::sorted.
/**
* Returns a comparator that will act be based on the how well the objects match the query.
* @param filter Query to use to compare the objects
* @param <T> Type of data that will be passed in.
* @return Comparator suitable for a sort() or sorted() call.
*/
public static <T> Comparator<T> comparator(QueryFilter<T> filter) { return new QueryComparator<>(filter);}Additional Methods I found helpful.
I added a few other methods that I found helpful. Here they are.
/**
* Returns a stream with the elements filtered based on the provided query
* @param list List of elements to filter and generate stream.
* @param query Query to apply to List.
* @param <T> Type of data that will be passed in.
* @return stream returns a stream of elements based on the query.
*/
public static <T> Stream<T> stream(List<T> list, QueryFilter<T> query) {
return list.stream().filter(Query.filter(query)).sorted(Query.comparator(query));
}Takes a list returns a stream that is filtered and sorted.
/**
* Returns a stream with the elements filtered based on the provided query
* @param array Array of elements to filter and generate stream.
* @param query Query to apply to List.
* @param <T> Type of data that will be passed in.
* @return stream returns a stream of elements based on the query.
*/
public static <T> Stream<T> stream(T[] array, QueryFilter<T> query) {
return Stream.of(array).filter(Query.filter(query)).sorted(Query.comparator(query));
}Takes an array and returns a stream that is filtered and sorted.
/**
* Returns a collection with the elements filtered based on the provided query
* @param list List of elements to filter and generate stream.
* @param query Query to apply to List.
* @param <T> Type of data that will be passed in.
* @param <R> Type of data that will be returned.
* @return stream returns a collection of elements based on the query.
*/
public static <T,A,R> R collect(List<T> list, QueryFilter<T> query, Collector<? super T,A,R> collector) {
return Query.stream(list,query).collect(collector);
}Takes a list and collector will return a collection of the filtered and sorted data.
/**
* Returns a collection with the elements filtered based on the provided query
* @param array List of elements to filter and generate stream.
* @param query Query to apply to List.
* @param <T> Type of data that will be passed in.
* @param <R> Type of data that will be returned.
* @return stream returns a collection of elements based on the query.
*/
public static <T,A,R> R collect(T[] array, QueryFilter<T> query, Collector<? super T,A,R> collector) {
return Query.stream(array,query).collect(collector);
}Takes an array and collector will return a collection of the filtered and sorted data.
/**
* Processes each matching element filtered based on the provided query
* @param list List of elements to filter and generate stream.
* @param query Query to apply to List.
* @param <T> Type of data that will be passed in.
* @return stream returns a collection of elements based on the query.
*/
public static <T> void forEach(List<T> list, QueryFilter<T> query, Consumer<? super T> action) {
Query.stream(list,query).forEach(action);
}Takes a list and Consumer to process on the filtered and sorted data.
/**
* Processes each matching element filtered based on the provided query
* @param array Array of elements to filter and generate stream.
* @param query Query to apply to List.
* @param <T> Type of data that will be passed in.
* @return stream returns a collection of elements based on the query.
*/
public static <T> void forEach(T[]array, QueryFilter<T> query, Consumer<? super T> action) {
Query.stream(array,query).forEach(action);
}Takes an array and Consumer to process on the filtered and sorted data.
GitHub
The latest versions of these files can be found here: mymiller_extensions