com.eclipsesource.json.JsonObject Maven / Gradle / Ivy
/*******************************************************************************
* Copyright (c) 2008, 2013 EclipseSource.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* Ralf Sternberg - initial implementation and API
******************************************************************************/
package com.eclipsesource.json;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.Reader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import com.eclipsesource.json.JsonObject.Member;
/**
* Represents a JSON object, i.e. an unordered set of name/value pairs, where the names are strings
* and the values are JSON values.
*
* Members can be added using the add(String, ...) methods which accept instances of
* {@link JsonValue}, strings, primitive numbers, and boolean values. To modify certain values of an
* object, use the set(String, ...) methods. Please note that the add
* methods are faster than set as they do not search for existing members. On the other
* hand, the add methods do not prevent adding multiple members with the same name.
* Duplicate names are discouraged but not prohibited by JSON.
*
*
* Members can be accessed by their name using {@link #get(String)}. A list of all names can be
* obtained from the method {@link #names()}. This class also supports iterating over the members in
* document order using an {@link #iterator()} or an enhanced for loop:
*
*
*
* for( Member member : jsonObject ) {
* String name = member.getName();
* JsonValue value = member.getValue();
* ...
* }
*
*
* Even though JSON objects are unordered by definition, instances of this class preserve the order
* of members to allow processing in document order and to guarantee a predictable output.
*
*
* Note that this class is not thread-safe. If multiple threads access a
* JsonObject instance concurrently, while at least one of these threads modifies the
* contents of this object, access to the instance must be synchronized externally. Failure to do so
* may lead to an inconsistent state.
*
*
* This class is not supposed to be extended by clients.
*
*/
@SuppressWarnings( "serial" )
// use default serial UID
public class JsonObject extends JsonValue implements Iterable {
private final List names;
private final List values;
private transient HashIndexTable table;
/**
* Creates a new empty JsonObject.
*/
public JsonObject() {
names = new ArrayList();
values = new ArrayList();
table = new HashIndexTable();
}
/**
* Creates a new JsonObject, initialized with the contents of the specified JSON object.
*
* @param object
* the JSON object to get the initial contents from, must not be null
*/
public JsonObject( JsonObject object ) {
this( object, false );
}
private JsonObject( JsonObject object, boolean unmodifiable ) {
if( object == null ) {
throw new NullPointerException( "object is null" );
}
if( unmodifiable ) {
names = Collections.unmodifiableList( object.names );
values = Collections.unmodifiableList( object.values );
} else {
names = new ArrayList( object.names );
values = new ArrayList( object.values );
}
table = new HashIndexTable();
updateHashIndex();
}
public void copyFrom(JsonObject object) {
if (object == null) {
throw new NullPointerException("object is null");
}
names.clear();
names.addAll(object.names);
values.clear();
values.addAll(object.values);
table = new HashIndexTable();
updateHashIndex();
}
/**
* Reads a JSON object from the given reader.
*
* Characters are read in chunks and buffered internally, therefore wrapping an existing reader in
* an additional BufferedReader does not improve reading
* performance.
*
*
* @param reader
* the reader to read the JSON object from
* @return the JSON object that has been read
* @throws IOException
* if an I/O error occurs in the reader
* @throws ParseException
* if the input is not valid JSON
* @throws UnsupportedOperationException
* if the input does not contain a JSON object
*/
public static JsonObject readFrom( Reader reader ) throws IOException {
return JsonValue.readFrom( reader ).asObject();
}
/**
* Reads a JSON object from the given string.
*
* @param string
* the string that contains the JSON object
* @return the JSON object that has been read
* @throws ParseException
* if the input is not valid JSON
* @throws UnsupportedOperationException
* if the input does not contain a JSON object
*/
public static JsonObject readFrom( String string ) {
return JsonValue.readFrom( string ).asObject();
}
/**
* Returns an unmodifiable JsonObject for the specified one. This method allows to provide
* read-only access to a JsonObject.
*
* The returned JsonObject is backed by the given object and reflect changes that happen to it.
* Attempts to modify the returned JsonObject result in an
* UnsupportedOperationException.
*
*
* @param object
* the JsonObject for which an unmodifiable JsonObject is to be returned
* @return an unmodifiable view of the specified JsonObject
*/
public static JsonObject unmodifiableObject( JsonObject object ) {
return new JsonObject( object, true );
}
/**
* Appends a new member to the end of this object, with the specified name and the JSON
* representation of the specified int value.
*
* This method does not prevent duplicate names. Calling this method with a name
* that already exists in the object will append another member with the same name. In order to
* replace existing members, use the method set(name, value) instead. However,
* add is much faster than set (because it does not need to
* search for existing members). Therefore add should be preferred when constructing new
* objects.
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add
* @return the object itself, to enable method chaining
*/
public JsonObject add( String name, int value ) {
add( name, valueOf( value ) );
return this;
}
/**
* Appends a new member to the end of this object, with the specified name and the JSON
* representation of the specified long value.
*
* This method does not prevent duplicate names. Calling this method with a name
* that already exists in the object will append another member with the same name. In order to
* replace existing members, use the method set(name, value) instead. However,
* add is much faster than set (because it does not need to
* search for existing members). Therefore add should be preferred when constructing new
* objects.
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add
* @return the object itself, to enable method chaining
*/
public JsonObject add( String name, long value ) {
add( name, valueOf( value ) );
return this;
}
/**
* Appends a new member to the end of this object, with the specified name and the JSON
* representation of the specified float value.
*
* This method does not prevent duplicate names. Calling this method with a name
* that already exists in the object will append another member with the same name. In order to
* replace existing members, use the method set(name, value) instead. However,
* add is much faster than set (because it does not need to
* search for existing members). Therefore add should be preferred when constructing new
* objects.
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add
* @return the object itself, to enable method chaining
*/
public JsonObject add( String name, float value ) {
add( name, valueOf( value ) );
return this;
}
/**
* Appends a new member to the end of this object, with the specified name and the JSON
* representation of the specified double value.
*
* This method does not prevent duplicate names. Calling this method with a name
* that already exists in the object will append another member with the same name. In order to
* replace existing members, use the method set(name, value) instead. However,
* add is much faster than set (because it does not need to
* search for existing members). Therefore add should be preferred when constructing new
* objects.
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add
* @return the object itself, to enable method chaining
*/
public JsonObject add( String name, double value ) {
add( name, valueOf( value ) );
return this;
}
/**
* Appends a new member to the end of this object, with the specified name and the JSON
* representation of the specified boolean value.
*
* This method does not prevent duplicate names. Calling this method with a name
* that already exists in the object will append another member with the same name. In order to
* replace existing members, use the method set(name, value) instead. However,
* add is much faster than set (because it does not need to
* search for existing members). Therefore add should be preferred when constructing new
* objects.
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add
* @return the object itself, to enable method chaining
*/
public JsonObject add( String name, boolean value ) {
add( name, valueOf( value ) );
return this;
}
/**
* Appends a new member to the end of this object, with the specified name and the JSON
* representation of the specified string.
*
* This method does not prevent duplicate names. Calling this method with a name
* that already exists in the object will append another member with the same name. In order to
* replace existing members, use the method set(name, value) instead. However,
* add is much faster than set (because it does not need to
* search for existing members). Therefore add should be preferred when constructing new
* objects.
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add
* @return the object itself, to enable method chaining
*/
public JsonObject add( String name, String value ) {
add( name, valueOf( value ) );
return this;
}
/**
* Appends a new member to the end of this object, with the specified name and the specified JSON
* value.
*
* This method does not prevent duplicate names. Calling this method with a name
* that already exists in the object will append another member with the same name. In order to
* replace existing members, use the method set(name, value) instead. However,
* add is much faster than set (because it does not need to
* search for existing members). Therefore add should be preferred when constructing new
* objects.
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add, must not be null
* @return the object itself, to enable method chaining
*/
public JsonObject add( String name, JsonValue value ) {
if( name == null ) {
throw new NullPointerException( "name is null" );
}
if( value == null ) {
throw new NullPointerException( "value is null" );
}
table.add( name, names.size() );
names.add( name );
values.add( value );
return this;
}
/**
* Sets the value of the member with the specified name to the JSON representation of the
* specified int value. If this object does not contain a member with this name, a
* new member is added at the end of the object. If this object contains multiple members with
* this name, only the last one is changed.
*
* This method should only be used to modify existing objects. To fill a new
* object with members, the method add(name, value) should be preferred which is much
* faster (as it does not need to search for existing members).
*
*
* @param name
* the name of the member to replace
* @param value
* the value to set to the member
* @return the object itself, to enable method chaining
*/
public JsonObject set( String name, int value ) {
set( name, valueOf( value ) );
return this;
}
/**
* Sets the value of the member with the specified name to the JSON representation of the
* specified long value. If this object does not contain a member with this name, a
* new member is added at the end of the object. If this object contains multiple members with
* this name, only the last one is changed.
*
* This method should only be used to modify existing objects. To fill a new
* object with members, the method add(name, value) should be preferred which is much
* faster (as it does not need to search for existing members).
*
*
* @param name
* the name of the member to replace
* @param value
* the value to set to the member
* @return the object itself, to enable method chaining
*/
public JsonObject set( String name, long value ) {
set( name, valueOf( value ) );
return this;
}
/**
* Sets the value of the member with the specified name to the JSON representation of the
* specified float value. If this object does not contain a member with this name, a
* new member is added at the end of the object. If this object contains multiple members with
* this name, only the last one is changed.
*
* This method should only be used to modify existing objects. To fill a new
* object with members, the method add(name, value) should be preferred which is much
* faster (as it does not need to search for existing members).
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add
* @return the object itself, to enable method chaining
*/
public JsonObject set( String name, float value ) {
set( name, valueOf( value ) );
return this;
}
/**
* Sets the value of the member with the specified name to the JSON representation of the
* specified double value. If this object does not contain a member with this name, a
* new member is added at the end of the object. If this object contains multiple members with
* this name, only the last one is changed.
*
* This method should only be used to modify existing objects. To fill a new
* object with members, the method add(name, value) should be preferred which is much
* faster (as it does not need to search for existing members).
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add
* @return the object itself, to enable method chaining
*/
public JsonObject set( String name, double value ) {
set( name, valueOf( value ) );
return this;
}
/**
* Sets the value of the member with the specified name to the JSON representation of the
* specified boolean value. If this object does not contain a member with this name,
* a new member is added at the end of the object. If this object contains multiple members with
* this name, only the last one is changed.
*
* This method should only be used to modify existing objects. To fill a new
* object with members, the method add(name, value) should be preferred which is much
* faster (as it does not need to search for existing members).
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add
* @return the object itself, to enable method chaining
*/
public JsonObject set( String name, boolean value ) {
set( name, valueOf( value ) );
return this;
}
/**
* Sets the value of the member with the specified name to the JSON representation of the
* specified string. If this object does not contain a member with this name, a new member is
* added at the end of the object. If this object contains multiple members with this name, only
* the last one is changed.
*
* This method should only be used to modify existing objects. To fill a new
* object with members, the method add(name, value) should be preferred which is much
* faster (as it does not need to search for existing members).
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add
* @return the object itself, to enable method chaining
*/
public JsonObject set( String name, String value ) {
set( name, valueOf( value ) );
return this;
}
public JsonObject set( String name, Object value ) {
set( name, valueOf( value ) );
return this;
}
/**
* Sets the value of the member with the specified name to the specified JSON value. If this
* object does not contain a member with this name, a new member is added at the end of the
* object. If this object contains multiple members with this name, only the last one is changed.
*
* This method should only be used to modify existing objects. To fill a new
* object with members, the method add(name, value) should be preferred which is much
* faster (as it does not need to search for existing members).
*
*
* @param name
* the name of the member to add
* @param value
* the value of the member to add, must not be null
* @return the object itself, to enable method chaining
*/
public JsonObject set( String name, JsonValue value ) {
if( name == null ) {
throw new NullPointerException( "name is null" );
}
if( value == null ) {
throw new NullPointerException( "value is null" );
}
int index = indexOf( name );
if( index != -1 ) {
values.set( index, value );
} else {
table.add( name, names.size() );
names.add( name );
values.add( value );
}
return this;
}
/**
* Removes a member with the specified name from this object. If this object contains multiple
* members with the given name, only the last one is removed. If this object does not contain a
* member with the specified name, the object is not modified.
*
* @param name
* the name of the member to remove
* @return the object itself, to enable method chaining
*/
public JsonObject remove( String name ) {
if( name == null ) {
throw new NullPointerException( "name is null" );
}
int index = indexOf( name );
if( index != -1 ) {
table.remove( index );
names.remove( index );
values.remove( index );
}
return this;
}
/**
* Returns the value of the member with the specified name in this object. If this object contains
* multiple members with the given name, this method will return the last one.
*
* @param name
* the name of the member whose value is to be returned
* @return the value of the last member with the specified name, or null if this
* object does not contain a member with that name
*/
public JsonValue get( String name ) {
if( name == null ) {
throw new NullPointerException( "name is null" );
}
int index = indexOf( name );
return index != -1 ? values.get( index ) : null;
}
/**
* Returns the number of members (i.e. name/value pairs) in this object.
*
* @return the number of members in this object
*/
public int size() {
return names.size();
}
/**
* Returns true if this object contains no members.
*
* @return true if this object contains no members
*/
public boolean isEmpty() {
return names.isEmpty();
}
/**
* Returns a list of the names in this object in document order. The returned list is backed by
* this object and will reflect subsequent changes. It cannot be used to modify this object.
* Attempts to modify the returned list will result in an exception.
*
* @returns a list of the names in this object
*/
public List names() {
return Collections.unmodifiableList( names );
}
/**
* Returns an iterator over the members of this object in document order. The returned iterator
* cannot be used to modify this object.
*
* @return an iterator over the members of this object
*/
public Iterator iterator() {
final Iterator namesIterator = names.iterator();
final Iterator valuesIterator = values.iterator();
return new Iterator() {
public boolean hasNext() {
return namesIterator.hasNext();
}
public Member next() {
String name = namesIterator.next();
JsonValue value = valuesIterator.next();
return new Member( name, value );
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
@Override
protected void write( JsonWriter writer ) throws IOException {
writer.writeObject( this );
}
@Override
public boolean isObject() {
return true;
}
@Override
public JsonObject asObject() {
return this;
}
@Override
public int hashCode() {
int result = 1;
result = 31 * result + names.hashCode();
result = 31 * result + values.hashCode();
return result;
}
@Override
public boolean equals( Object obj ) {
if( this == obj ) {
return true;
}
if( obj == null ) {
return false;
}
if( getClass() != obj.getClass() ) {
return false;
}
JsonObject other = (JsonObject)obj;
return names.equals( other.names ) && values.equals( other.values );
}
int indexOf( String name ) {
int index = table.get( name );
if( index != -1 && name.equals( names.get( index ) ) ) {
return index;
}
return names.lastIndexOf( name );
}
private synchronized void readObject( ObjectInputStream inputStream ) throws IOException,
ClassNotFoundException
{
inputStream.defaultReadObject();
table = new HashIndexTable();
updateHashIndex();
}
private void updateHashIndex() {
int size = names.size();
for( int i = 0; i < size; i++ ) {
table.add( names.get( i ), i );
}
}
/**
* Represents a member of a JSON object, i.e. a pair of name and value.
*/
public static class Member {
private final String name;
private final JsonValue value;
Member( String name, JsonValue value ) {
this.name = name;
this.value = value;
}
/**
* Returns the name of this member.
*
* @return the name of this member, never null
*/
public String getName() {
return name;
}
/**
* Returns the value of this member.
*
* @return the value of this member, never null
*/
public JsonValue getValue() {
return value;
}
@Override
public int hashCode() {
int result = 1;
result = 31 * result + name.hashCode();
result = 31 * result + value.hashCode();
return result;
}
@Override
public boolean equals( Object obj ) {
if( this == obj ) {
return true;
}
if( obj == null ) {
return false;
}
if( getClass() != obj.getClass() ) {
return false;
}
Member other = (Member)obj;
return name.equals( other.name ) && value.equals( other.value );
}
}
static class HashIndexTable {
private final byte[] hashTable = new byte[32]; // must be a power of two
public HashIndexTable() {
}
public HashIndexTable( HashIndexTable original ) {
System.arraycopy( original.hashTable, 0, hashTable, 0, hashTable.length );
}
void add( String name, int index ) {
int slot = hashSlotFor( name );
if( index < 0xff ) {
// increment by 1, 0 stands for empty
hashTable[slot] = (byte)( index + 1 );
} else {
hashTable[slot] = 0;
}
}
void remove( int index ) {
for( int i = 0; i < hashTable.length; i++ ) {
if( hashTable[i] == index + 1 ) {
hashTable[i] = 0;
} else if( hashTable[i] > index + 1 ) {
hashTable[i]--;
}
}
}
int get( Object name ) {
int slot = hashSlotFor( name );
// subtract 1, 0 stands for empty
return ( hashTable[slot] & 0xff ) - 1;
}
private int hashSlotFor( Object element ) {
return element.hashCode() & hashTable.length - 1;
}
}
}