// BasicDBObjectBuilder.java
/**
* Copyright (C) 2008 10gen Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.mongodb;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
/**
* utility for building complex objects
* example:
* BasicDBObjectBuilder.start().add( "name" , "eliot" ).add( "number" , 17 ).get()
*/
public class BasicDBObjectBuilder {
/**
* creates an empty object
*/
public BasicDBObjectBuilder(){
_stack = new LinkedList<DBObject>();
_stack.add( new BasicDBObject() );
}
/**
* Creates an empty object
* @return The new empty builder
*/
public static BasicDBObjectBuilder start(){
return new BasicDBObjectBuilder();
}
/**
* creates an object with the given key/value
* @param k The field name
* @param val The value
*/
public static BasicDBObjectBuilder start( String k , Object val ){
return (new BasicDBObjectBuilder()).add( k , val );
}
/**
* Creates an object builder from an existing map.
* @param m map to use
* @return the new builder
*/
@SuppressWarnings("unchecked")
public static BasicDBObjectBuilder start(Map m){
BasicDBObjectBuilder b = new BasicDBObjectBuilder();
Iterator<Map.Entry> i = m.entrySet().iterator();
while (i.hasNext()) {
Map.Entry entry = i.next();
b.add(entry.getKey().toString(), entry.getValue());
}
return b;
}
/**
* appends the key/value to the active object
* @param key
* @param val
* @return returns itself so you can chain
*/
public BasicDBObjectBuilder append( String key , Object val ){
_cur().put( key , val );
return this;
}
/**
* same as appends
* @see #append(String, Object)
* @param key
* @param val
* @return returns itself so you can chain
*/
public BasicDBObjectBuilder add( String key , Object val ){
return append( key, val );
}
/**
* creates an new empty object and inserts it into the current object with the given key.
* The new child object becomes the active one.
* @param key
* @return returns itself so you can chain
*/
public BasicDBObjectBuilder push( String key ){
BasicDBObject o = new BasicDBObject();
_cur().put( key , o );
_stack.addLast( o );
return this;
}
/**
* pops the active object, which means that the parent object becomes active
* @return returns itself so you can chain
*/
public BasicDBObjectBuilder pop(){
if ( _stack.size() <= 1 )
throw new IllegalArgumentException( "can't pop last element" );
_stack.removeLast();
return this;
}
/**
* gets the base object
* @return The base object
*/
public DBObject get(){
return _stack.getFirst();
}
/**
* returns true if no key/value was inserted into base object
* @return True if empty
*/
public boolean isEmpty(){
return ((BasicDBObject) _stack.getFirst()).size() == 0;
}
private DBObject _cur(){
return _stack.getLast();
}
private final LinkedList<DBObject> _stack;
}