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Introduce random JsonPath function #4

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Mar 1, 2024
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Introduce random JsonPath function #4

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32 changes: 17 additions & 15 deletions README.md
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Expand Up @@ -58,21 +58,23 @@ Functions
Functions can be invoked at the tail end of a path - the input to a function is the output of the path expression.
The function output is dictated by the function itself.

| Function | Description | Output type |
|:------------|:-------------------------------------------------------------------------------------|:---------------------|
| `min()` | Provides the min value of an array of numbers | Double |
| `max()` | Provides the max value of an array of numbers | Double |
| `avg()` | Provides the average value of an array of numbers | Double |
| `stddev()` | Provides the standard deviation value of an array of numbers | Double |
| `length()` | Provides the length of an array | Integer |
| `sum()` | Provides the sum value of an array of numbers | Double |
| `keys()` | Provides the property keys (An alternative for terminal tilde `~`) | `Set<E>` |
| `concat(X)` | Provides a concatinated version of the path output with a new item | like input |
| `append(X)` | add an item to the json path output array | like input |
| `first()` | Provides the first item of an array | Depends on the array |
| `last()` | Provides the last item of an array | Depends on the array |
| `index(X)` | Provides the item of an array of index: X, if the X is negative, take from backwards | Depends on the array |
| `distinct()`| Provides an array containing only unique items from the input array | List<E> |
| Function | Description | Output type |
|:------------|:---------------------------------------------------------------------------------------|:---------------------|
| `min()` | Provides the min value of an array of numbers | Double |
| `max()` | Provides the max value of an array of numbers | Double |
| `avg()` | Provides the average value of an array of numbers | Double |
| `stddev()` | Provides the standard deviation value of an array of numbers | Double |
| `length()` | Provides the length of an array | Integer |
| `sum()` | Provides the sum value of an array of numbers | Double |
| `keys()` | Provides the property keys (An alternative for terminal tilde `~`) | `Set<E>` |
| `concat(X)` | Provides a concatinated version of the path output with a new item | like input |
| `append(X)` | add an item to the json path output array | like input |
| `first()` | Provides the first item of an array | Depends on the array |
| `last()` | Provides the last item of an array | Depends on the array |
| `index(X)` | Provides the item of an array of index: X, if the X is negative, take from backwards | Depends on the array |
| `distinct()`| Provides an array containing only unique items from the input array | List<E> |
| `random()` | Provides one random item from the array | Depends on the array |

Filter Operators
-----------------

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2 changes: 2 additions & 0 deletions json-path/src/main/java/com/jayway/jsonpath/internal/function/PathFunctionFactory.java
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Expand Up @@ -12,6 +12,7 @@
import com.jayway.jsonpath.internal.function.sequence.First;
import com.jayway.jsonpath.internal.function.sequence.Index;
import com.jayway.jsonpath.internal.function.sequence.Last;
import com.jayway.jsonpath.internal.function.sequence.Random;
import com.jayway.jsonpath.internal.function.text.Concatenate;
import com.jayway.jsonpath.internal.function.text.Length;

Expand Down Expand Up @@ -56,6 +57,7 @@ public class PathFunctionFactory {
map.put("last", Last.class);
map.put("distinct", Distinct.class);
map.put("index", Index.class);
map.put("random", Random.class);


FUNCTIONS = Collections.unmodifiableMap(map);
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34 changes: 34 additions & 0 deletions json-path/src/main/java/com/jayway/jsonpath/internal/function/sequence/Random.java
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@@ -0,0 +1,34 @@
package com.jayway.jsonpath.internal.function.sequence;

import com.jayway.jsonpath.JsonPathException;
import com.jayway.jsonpath.internal.EvaluationContext;
import com.jayway.jsonpath.internal.PathRef;
import com.jayway.jsonpath.internal.function.Parameter;
import com.jayway.jsonpath.internal.function.PathFunction;

import java.security.SecureRandom;
import java.util.List;
import java.util.stream.Collectors;
import java.util.stream.StreamSupport;

/**
* Take a random item from collection of JSONArray
*/
public class Random implements PathFunction {
@Override
public Object invoke(String currentPath, PathRef parent, Object model, EvaluationContext ctx, List<Parameter> parameters) {
if (ctx.configuration().jsonProvider().isArray(model)) {
Iterable<?> objects = ctx.configuration().jsonProvider().toIterable(model);
List<?> elements = StreamSupport.stream(objects.spliterator(), false)
.collect(Collectors.toList());

if (elements.isEmpty()) {
throw new JsonPathException("Aggregation function attempted to get a random item from empty array");
}

SecureRandom rand = new SecureRandom();
return elements.get(rand.nextInt(elements.size()));
}
throw new JsonPathException("Aggregation function attempted to get a random item from not array");
}
}
6 changes: 5 additions & 1 deletion json-path/src/test/java/com/jayway/jsonpath/internal/function/BaseFunctionTest.java
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Expand Up @@ -40,8 +40,12 @@ public class BaseFunctionTest {
* The expected value to be returned from the test
*/
protected void verifyFunction(Configuration conf, String pathExpr, String json, Object expectedValue) {
assertThat(evaluate(conf, pathExpr, json)).isEqualTo(expectedValue);
}

protected Object evaluate(Configuration conf, String pathExpr, String json) {
Object result = using(conf).parse(json).read(pathExpr);
assertThat(conf.jsonProvider().unwrap(result)).isEqualTo(expectedValue);
return conf.jsonProvider().unwrap(result);
}

protected void verifyMathFunction(Configuration conf, String pathExpr, Object expectedValue) {
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17 changes: 17 additions & 0 deletions ...-path/src/test/java/com/jayway/jsonpath/internal/function/SequentialPathFunctionTest.java
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@@ -1,11 +1,13 @@
package com.jayway.jsonpath.internal.function;

import static com.jayway.jsonpath.JsonPath.using;
import static org.assertj.core.api.Assertions.assertThat;

import com.fasterxml.jackson.databind.ObjectMapper;
import com.jayway.jsonpath.Configuration;
import com.jayway.jsonpath.Configurations;
import java.util.Arrays;
import java.util.List;

import com.jayway.jsonpath.spi.json.JacksonJsonProvider;
import com.jayway.jsonpath.spi.mapper.JacksonMappingProvider;
Expand All @@ -18,6 +20,7 @@
* -last
* -index(X)
* -distinct
* -random
*
* Created by git9527 on 6/11/22.
*/
Expand Down Expand Up @@ -90,4 +93,18 @@ public void testDistinctOfEmptyObjects() throws Exception {
final Object expectedValue = Configuration.defaultConfiguration().jsonProvider().parse("[]");
verifyFunction(conf, "$.empty.distinct()", OBJECT_SERIES, expectedValue);
}

@Test
public void testRandomForStrings() throws Exception {
List<Object> elements = (List<Object>) evaluate(conf, "$.text", TEXT_AND_NUMBER_SERIES);
Object randomElement = evaluate(conf, "$.text.random()", TEXT_AND_NUMBER_SERIES);
assertThat(randomElement).isInstanceOf(String.class).isIn(elements);
}

@Test
public void testRandomForNumbers() throws Exception {
List<Object> elements = (List<Object>) evaluate(conf, "$.numbers", TEXT_AND_NUMBER_SERIES);
Object randomElement = evaluate(conf, "$.numbers.random()", TEXT_AND_NUMBER_SERIES);
assertThat(randomElement).isInstanceOf(Integer.class).isIn(elements);
}
}
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