Java MongoDB : Delete document（译）

 

原文出自：http://www.mkyong.com/mongodb/java-mongodb-delete-document/

返回目录：http://ysj5125094.iteye.com/blog/2192754  

 

Java MongoDB : Delete document

In this tutorial, we show you how to use collection.remove() to delete documents from the collection.

译：在本教程中，我们将向你展示使用 collection.remove() 从集合中删除文档。

1. Test Data

Insert 10 documents from number 1 to 10 for testing.

译：插入number 为 1 到 10的 10条文档。

 

for (int i=1; i <= 10; i++) {
    collection.insert(new BasicDBObject().append("number", i));
}

 

2. DBCollection.remove()

See below code snippets to delete documents.（译：看下面删除文档的代码片断）

Example 1

Get first document and delete it. In this case, number = 1 is deleted. 

译：获取第一个文档并删除他，相当于删除number = 1的文档。

 

	DBObject doc = collection.findOne(); //get first document
	collection.remove(doc);

 

Example 2

Puts query in a BasicDBObject. In this case, number = 2 is deleted. 

译：向BasicDBObject对象中put一个number = 2 ，再删除。

 

	BasicDBObject document = new BasicDBObject();
	document.put("number", 2);
	collection.remove(document);

 

 

And Operator?（译：and 操作符）

 

Two common mistakes :（译：两个常见的错误）

1. A query like this only delete number = 3.

译：只删除number=3的。

	BasicDBObject document = new BasicDBObject();
	document.put("number", 2);
        document.put("number", 3); //override above value 2，会重写上面的值
	collection.remove(document);

2. Nice try below, but query like this will not work, it will delete NOTHING.

译：这是种不错的尝试，但是这种尝试，将不会删除任何数据。

	BasicDBObject document = new BasicDBObject();
	List<Integer> list = new ArrayList<Integer>();
	list.add(7);
	list.add(8);
	document.put("number", list);
	collection.remove(document);

 

For “AND” query, you need to use “$in” or “$and” operator, see example 5.

译：使用"AND"查询，你需要使用"$in" 或 "$and"操作符，see example 5.

 

Example 3

Use BasicDBObject directly. In this case, number = 3 is deleted.

译：直接使用BasicDBObject 对象。在这种情况下，number=3是可以删除的。

 

collection.remove(new BasicDBObject().append("number", 3));

 

Example 4

Puts a $gt operator in a BasicDBObject object. In this case, number = 10 is deleted. 

译：将 $gt 操作符put BasicDBObject对象。在这种情况下，number=10是可以删除的。

 

	BasicDBObject query = new BasicDBObject();
	query.put("number", new BasicDBObject("$gt", 9));
	collection.remove(query);

 

Example 5

Puts a $in operator in a BasicDBObject object, constructs the query in ArrayList. In this case, number = 4 and number = 5 are deleted. 

译：put一个 $in 操作符到 BasicDBObject 对象，构建查询列表。在这种情况下，number=4和number=5被删除。

 

	BasicDBObject query2 = new BasicDBObject();
	List<Integer> list = new ArrayList<Integer>();
	list.add(4);
	list.add(5);
	query2.put("number", new BasicDBObject("$in", list));
	collection.remove(query2);

More MongoDB Operators
For more operators, read this MongoDB operators quick reference. 

 

译：更多操作符，请阅读此文档（MongoDB operators quick reference.）。

 

Example 6

Use cursor to delete all available documents. (Not recommended, prefer example 7)

译：使用游标，删除所有可用文档（不推荐使用，建议选择example 7）

 

	DBCursor cursor = collection.find();
	while (cursor.hasNext()) {
		collection.remove(cursor.next());
	}

 

Example 7

Pass an empty BasicDBObject, and the entire documents will be deleted. 

译：传递一个空的 BasicDBObject 对象，整个文档会被删除。

 

collection.remove(new BasicDBObject());

 

Example 8

It deletes the entire documents and drop the collection. 

译：删除所有文档及整个集合。

 

collection.drop();

 

Example 9

The remove() will returns a WrireResult object, it contains useful information about the remove operation. And you can uses getN() to get the number of documents affected. 

译：使用 remove() 命令将返回一个 WrireResult 对象，他包含删除操作的信息，你可以使用 getN() 方法得到影响文档的行数。

       WriteResult result = collection.remove(query2);
       System.out.println("Number of documents are deleted : " + result.getN());

3. Full Example

Full example to show the different ways to delete documents. 

package com.mkyong.core;
 
import java.net.UnknownHostException;
import java.util.ArrayList;
import java.util.List;
 
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.DBObject;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
 
/**
 * Java MongoDB : Delete document
 * @author mkyong
 */
 
public class App {
    public static void main(String[] args) {
 
      try {
 
	Mongo mongo = new Mongo("localhost", 27017);
	DB db = mongo.getDB("yourdb");
 
	// get a single collection
	DBCollection collection = db.getCollection("dummyColl");
 
	//insert number 1 to 10 for testing
	for (int i=1; i <= 10; i++) {
		collection.insert(new BasicDBObject().append("number", i));
	}
 
	//remove number = 1
	DBObject doc = collection.findOne(); //get first document
	collection.remove(doc);
 
	//remove number = 2
	BasicDBObject document = new BasicDBObject();
	document.put("number", 2);
	collection.remove(document);
 
	//remove number = 3
	collection.remove(new BasicDBObject().append("number", 3));
 
	//remove number > 9 , means delete number = 10
	BasicDBObject query = new BasicDBObject();
	query.put("number", new BasicDBObject("$gt", 9));
	collection.remove(query);
 
	//remove number = 4 and 5
	BasicDBObject query2 = new BasicDBObject();
	List<Integer> list = new ArrayList<Integer>();
	list.add(4);
	list.add(5);
	query2.put("number", new BasicDBObject("$in", list));
	collection.remove(query2);
 
	//print out the document
	DBCursor cursor = collection.find();
        while(cursor.hasNext()) {
             System.out.println(cursor.next());
        }
 
        collection.drop();
 
        System.out.println("Done");
 
      } catch (UnknownHostException e) {
	e.printStackTrace();
      } catch (MongoException e) {
	e.printStackTrace();
      }
 
   }
}

Output… 

{ "_id" : { "$oid" : "4dc7a6989e3a66c5faeee757"} , "number" : 6}
{ "_id" : { "$oid" : "4dc7a6989e3a66c5faeee758"} , "number" : 7}
{ "_id" : { "$oid" : "4dc7a6989e3a66c5faeee759"} , "number" : 8}
{ "_id" : { "$oid" : "4dc7a6989e3a66c5faeee75a"} , "number" : 9}
Done

References

1. MongoDB operators quick reference
2. MongoDB WriteResult JavaDoc