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Fixes #6558 - Allow configuring return type in JSON array parsing.
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Introduced `arrayConverter` in both JSON and AsyncJSON.Factory.

Signed-off-by: Simone Bordet <simone.bordet@gmail.com>
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@sbordet
sbordet committed Aug 2, 2021
1 parent 30a4257 commit 241f42c
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Showing 3 changed files with 131 additions and 7 deletions.
37 changes: 35 additions & 2 deletions jetty-util-ajax/src/main/java/org/eclipse/jetty/util/ajax/AsyncJSON.java
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Expand Up @@ -24,7 +24,9 @@
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;

import org.eclipse.jetty.util.ArrayTernaryTrie;
import org.eclipse.jetty.util.BufferUtil;
Expand Down Expand Up @@ -68,6 +70,8 @@
* </pre>
* <p>Class {@code com.acme.Person} must either implement {@link Convertible},
* or be mapped with a {@link Convertor} via {@link Factory#putConvertor(String, Convertor)}.</p>
* <p>JSON arrays are by default represented with a {@code List<Object>}, but the
* Java representation can be customized via {@link Factory#setArrayConverter(Function)}.</p>
*/
public class AsyncJSON
{
Expand All @@ -81,8 +85,31 @@ public static class Factory
{
private Trie<CachedString> cache;
private Map<String, Convertor> convertors;
private Function<List<?>, Object> arrayConverter = list -> list;
private boolean detailedParseException;

/**
* @return the function to customize the Java representation of JSON arrays
* @see #setArrayConverter(Function)
*/
public Function<List<?>, Object> getArrayConverter()
{
return arrayConverter;
}

/**
* <p>Sets the function to convert JSON arrays from their default Java
* representation, a {@code List<Object>}, to another Java data structure
* such as an {@code Object[]}.</p>
*
* @param arrayConverter the function to customize the Java representation of JSON arrays
* @see #getArrayConverter()
*/
public void setArrayConverter(Function<List<?>, Object> arrayConverter)
{
this.arrayConverter = Objects.requireNonNull(arrayConverter);
}

/**
* @return whether a parse failure should report the whole JSON string or just the last chunk
*/
Expand Down Expand Up @@ -873,9 +900,10 @@ private boolean parseArray(ByteBuffer buffer)
case ']':
{
buffer.get();
Object array = stack.peek().value;
@SuppressWarnings("unchecked")
List<Object> array = (List<Object>)stack.peek().value;
stack.pop();
stack.peek().value(array);
stack.peek().value(convertArray(array));
return true;
}
case ',':
Expand Down Expand Up @@ -1070,6 +1098,11 @@ private boolean parseObjectFieldValue(ByteBuffer buffer)
return true;
}

private Object convertArray(List<?> array)
{
return factory.getArrayConverter().apply(array);
}

private Object convertObject(Map<String, Object> object)
{
Object result = convertObject("x-class", object);
Expand Down
54 changes: 49 additions & 5 deletions jetty-util-ajax/src/main/java/org/eclipse/jetty/util/ajax/JSON.java
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Expand Up @@ -25,11 +25,14 @@
import java.lang.reflect.Array;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Objects;
import java.util.concurrent.ConcurrentHashMap;
import java.util.function.Function;

import org.eclipse.jetty.util.IO;
import org.eclipse.jetty.util.Loader;
Expand Down Expand Up @@ -94,6 +97,7 @@ public class JSON

private final Map<String, Convertor> _convertors = new ConcurrentHashMap<>();
private int _stringBufferSize = 1024;
private Function<List<?>, Object> _arrayConverter = List::toArray;

public JSON()
{
Expand Down Expand Up @@ -669,6 +673,12 @@ protected Map<String, Object> newMap()
return new HashMap<>();
}

/**
* @param size the size of the array
* @return a new array
* @deprecated use {@link #setArrayConverter(Function)} instead.
*/
@Deprecated
protected Object[] newArray(int size)
{
return new Object[size];
Expand Down Expand Up @@ -764,6 +774,39 @@ public void addConvertorFor(String name, Convertor convertor)
_convertors.put(name, convertor);
}

/**
* Removes a registered {@link JSON.Convertor} for the given named class or interface.
*
* @param name name of a class or an interface for a registered {@link JSON.Convertor}
* @return the {@link JSON.Convertor} that was removed, or null
*/
public Convertor removeConvertorFor(String name)
{
return _convertors.remove(name);
}

/**
* @return the function to customize the Java representation of JSON arrays
* @see #setArrayConverter(Function)
*/
public Function<List<?>, Object> getArrayConverter()
{
return _arrayConverter;
}

/**
* <p>Sets the function to convert JSON arrays from their default Java
* representation, a {@code List<Object>}, to another Java data structure
* such as an {@code Object[]}.</p>
*
* @param arrayConverter the function to customize the Java representation of JSON arrays
* @see #getArrayConverter()
*/
public void setArrayConverter(Function<List<?>, Object> arrayConverter)
{
_arrayConverter = Objects.requireNonNull(arrayConverter);
}

/**
* Lookup a convertor for a named class.
*
Expand Down Expand Up @@ -1047,14 +1090,15 @@ protected Object parseArray(Source source)
switch (size)
{
case 0:
return newArray(0);
list = Collections.emptyList();
break;
case 1:
Object array = newArray(1);
Array.set(array, 0, item);
return array;
list = Collections.singletonList(item);
break;
default:
return list.toArray(newArray(list.size()));
break;
}
return getArrayConverter().apply(list);

case ',':
if (comma)
Expand Down
47 changes: 47 additions & 0 deletions jetty-util-ajax/src/test/java/org/eclipse/jetty/util/ajax/AsyncJSONTest.java
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Expand Up @@ -24,15 +24,19 @@
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Function;

import org.hamcrest.Matchers;
import org.junit.jupiter.api.Test;
import org.junit.jupiter.params.ParameterizedTest;
import org.junit.jupiter.params.provider.MethodSource;
import org.junit.jupiter.params.provider.ValueSource;

import static java.nio.charset.StandardCharsets.UTF_8;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertFalse;
import static org.junit.jupiter.api.Assertions.assertNotNull;
import static org.junit.jupiter.api.Assertions.assertSame;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.assertTrue;
Expand Down Expand Up @@ -525,4 +529,47 @@ public void testEncodedCaching()
assertSame(foo, item);
}
}

@Test
public void testArrayConverter()
{
// Test root arrays.
testArrayConverter("[1]", Function.identity());

// Test non-root arrays.
testArrayConverter("{\"array\": [1]}", object ->
{
@SuppressWarnings("unchecked")
Map<String, Object> map = (Map<String, Object>)object;
return map.get("array");
});
}

private void testArrayConverter(String json, Function<Object, Object> extractor)
{
AsyncJSON.Factory factory = new AsyncJSON.Factory();
AsyncJSON async = factory.newAsyncJSON();
JSON sync = new JSON();

async.parse(UTF_8.encode(json));
Object result = extractor.apply(async.complete());
// AsyncJSON historically defaults to list.
assertThat(result, Matchers.instanceOf(List.class));
// JSON historically defaults to array.
result = extractor.apply(sync.parse(new JSON.StringSource(json)));
assertNotNull(result);
assertTrue(result.getClass().isArray(), json + " -> " + result);

// Configure AsyncJSON to return arrays.
factory.setArrayConverter(List::toArray);
async.parse(UTF_8.encode(json));
result = extractor.apply(async.complete());
assertNotNull(result);
assertTrue(result.getClass().isArray(), json + " -> " + result);

// Configure JSON to return lists.
sync.setArrayConverter(list -> list);
result = extractor.apply(sync.parse(new JSON.StringSource(json)));
assertThat(result, Matchers.instanceOf(List.class));
}
}

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