Java MongoDB : Update document（译）

 

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

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

 

Java MongoDB : Update document

In this tutorial, we show you how to use Java MongoDB API collection.update() to update documents.

译：在本教程中，我们将向您展示如何使用MongoDB Java API的 collection.update() 更新文件。

Test Data

 

Assume following data / documents are inserted.

译：假设以下是插入的数据/文件。

 

{
	"hosting" : "hostA",
	"type" : "vps",
	"clients" : 1000
},
{
	"hosting" : "hostB",
	"type" : "dedicated server",
	"clients" : 100
},
{
	"hosting" : "hostC",
	"type" : "vps",
	"clients" : 900
}

{ "_id" : { "$oid" : "id"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}

 

1. DBCollection.update() with $set

Find document where hosting = ‘hostB’, and update it’s clients values from 100 to 110.  

译：查找 hosting = 'hostB' 的文档并且更新 client 字段的值（从100改到110）。

 

	BasicDBObject newDocument = new BasicDBObject();
	newDocument.put("clients", 110);
 
	BasicDBObject searchQuery = new BasicDBObject().append("hosting", "hostB");
 
	collection.update(searchQuery, newDocument);

Output... 

 

 

{ "_id" : { "$oid" : "id"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{ "_id" : { "$oid" : "id"} , "clients" : 110}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}

The document is replaced!? （译：文件被替换了？）
Wait, the entire “hostB” document is replaced with another new document, this is not what we want.

 

译： 等等，整个 'hostB' 文档被另一个新的文档所取代了，这不是我们想要的结果。

 

To update a particular value only, uses $set update modifier.

译：更新一个特定的值，使用 $set 来处理。

 

	BasicDBObject newDocument = new BasicDBObject();
	newDocument.append("$set", new BasicDBObject().append("clients", 110));
 
	BasicDBObject searchQuery = new BasicDBObject().append("hosting", "hostB");
 
	collection.update(searchQuery, newDocument);

Output 

 

 

{ "_id" : { "$oid" : "id"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 110}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}

 

 

Note
The MongoDB team should create another new API named DBCollection.replace(), many beginners are trapped in this DBCollection.update() API and replace the entire document accidentally. Again, to update a particular value, use $set.

译：整个MongoDB团队应该创建一个新的API 取名 DBCollection.replace()，因为很多新手都受困于这个 DBCollection.update() API 和替换整个文档的意外之间。再次声明，更新一个特定的值要使用 $set。

2. DBCollection.update() with $inc

This example show the use of $inc modifier to increase a particular value. Find document where hosting = ‘hostB’, update it’s ‘clients’ value by increasing the value from 100 to 199, (100 + 99) = 199.

译：这个例子显示，使用 $inc 修改增加一个特定的值。查找到hosting = 'hostB'的文档用新增加特定的值 来修改 'clients' 字段的值，由100改成199（100+99=199）。

 

BasicDBObject newDocument = 
		new BasicDBObject().append("$inc", 
		new BasicDBObject().append("clients", 99));
/* 
BasicDBObject newDocument = 
		new BasicDBObject().append("$inc", 
		new BasicDBObject().append("total clients", 99));
*/

	collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument);

Output 

 

 

{ "_id" : { "$oid" : "id"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 199}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}

 

3. DBCollection.update() with multi

This example show the use of multi parameter to update a set of matched documents. Find document where type = ‘vps’, update all the matched documents’ ‘clients’ value to 888. 

译：这个例子显示，使用 multi 参数更新设置匹配的文档。查找type='vps'的文档，更新所有匹配文档的'clients'字段为888.

 

	BasicDBObject updateQuery = new BasicDBObject();
	updateQuery.append("$set", 
		new BasicDBObject().append("clients", "888"));
 
	BasicDBObject searchQuery = new BasicDBObject();
	searchQuery.append("type", "vps");
 
	collection.updateMulti(searchQuery, updateQuery);			
 
	//below statement set multi to true.
	//collection.update(searchQuery, updateQuery, false, true);

Output 

 

 

{ "_id" : { "$oid" : "id"} , "hosting" : "hostA" , "clients" : "888" , "type" : "vps"}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostC" , "clients" : "888" , "type" : "vps"}

Note
If update without the multi set to true. 

译：如果update的multi没有设置为true。

 

 

	BasicDBObject updateQuery = new BasicDBObject();
	updateQuery.append("$set", 
		new BasicDBObject().append("clients", "888"));
 
	BasicDBObject searchQuery = new BasicDBObject();
	searchQuery.append("type", "vps");
 
	collection.update(searchQuery, updateQuery);

You will noticed that only the first matched document is updated.

译：你会注意到，只有第一个匹配的文档更新。

{"_id":{ "$oid" : "x"} , "hosting" : "hostA" , "clients" : "888" , "type" : "vps"}
{"_id":{ "$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{"_id":{ "$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}

To update a set of matched documents, you need to set “multi” to true.

译：更新一组匹配的文件，你需要设置“multi”为true。

 

4. Full Example

Full example by combining above code snippets.

译：结合上面的代码片段的完整示例。

package com.mkyong.core;
 
import java.net.UnknownHostException;
import com.mongodb.BasicDBObject;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.DBCursor;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
 
/**
 * Java MongoDB update document
 * 
 * @author mkyong
 * 
 */
 
public class UpdateApp {
 
	public static void printAllDocuments(DBCollection collection) {
		DBCursor cursor = collection.find();
		while (cursor.hasNext()) {
			System.out.println(cursor.next());
		}
	}
 
	public static void removeAllDocuments(DBCollection collection) {
		collection.remove(new BasicDBObject());
	}
 
	public static void insertDummyDocuments(DBCollection collection) {
		BasicDBObject document = new BasicDBObject();
		document.put("hosting", "hostA");
		document.put("type", "vps");
		document.put("clients", 1000);
 
		BasicDBObject document2 = new BasicDBObject();
		document2.put("hosting", "hostB");
		document2.put("type", "dedicated server");
		document2.put("clients", 100);
 
		BasicDBObject document3 = new BasicDBObject();
		document3.put("hosting", "hostC");
		document3.put("type", "vps");
		document3.put("clients", 900);
 
		collection.insert(document);
		collection.insert(document2);
		collection.insert(document3);
	}
 
	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");
 
	  System.out.println("Testing 1...no $set");
 
	  insertDummyDocuments(collection);
 
	  // find hosting = hostB, and update the clients to 110
	  BasicDBObject newDocument = new BasicDBObject();
	  newDocument.put("clients", 110);
 
	  BasicDBObject searchQuery = new BasicDBObject().append("hosting", "hostB");
 
	  collection.update(searchQuery, newDocument);
 
	  printAllDocuments(collection);
	  removeAllDocuments(collection);
 
	  System.out.println("\nTesting 1...with $set");
 
	  insertDummyDocuments(collection);
 
	  BasicDBObject updateDocument = new BasicDBObject();
	  updateDocument.append("$set", new BasicDBObject().append("clients", 110));
 
	  BasicDBObject searchQuery2 = new BasicDBObject().append("hosting", "hostB");
 
	  collection.update(searchQuery2, updateDocument);
 
	  printAllDocuments(collection);
	  removeAllDocuments(collection);
 
	  System.out.println("\nTesting 2... with $inc");
	  insertDummyDocuments(collection);
	  // find hosting = hostB and increase it's "clients" value by 99
	  BasicDBObject newDocument2 = new BasicDBObject().append("$inc",
		new BasicDBObject().append("clients", 99));
 
	  collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument2);
 
	  printAllDocuments(collection);
	  removeAllDocuments(collection);
 
	  System.out.println("\nTesting 3... with $multi");
 
	  insertDummyDocuments(collection);
	  // find type = vps , update all matched documents , clients value to 888
	  BasicDBObject updateQuery = new BasicDBObject();
	  updateQuery.append("$set", new BasicDBObject().append("clients", "888"));
 
	  BasicDBObject searchQuery3 = new BasicDBObject();
	  searchQuery3.append("type", "vps");
 
	  collection.updateMulti(searchQuery3, updateQuery);
	  // collection.update(searchQuery3, updateQuery, false, true);
 
	  printAllDocuments(collection);
	  removeAllDocuments(collection);
 
	  System.out.println("Done");
 
	} catch (UnknownHostException e) {
		e.printStackTrace();
	} catch (MongoException e) {
		e.printStackTrace();
	}
 
    }
}

Output 

Testing 1...no $set
{ "_id" : { "$oid" : "id"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{ "_id" : { "$oid" : "id"} , "clients" : 110}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
 
Testing 1...with $set
{ "_id" : { "$oid" : "id"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 110}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
 
Testing 2... with $inc
{ "_id" : { "$oid" : "id"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 199}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
 
Testing 3... with $multi
{ "_id" : { "$oid" : "id"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{ "_id" : { "$oid" : "id"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
{ "_id" : { "$oid" : "id"} , "clients" : "888" , "hosting" : "hostA" , "type" : "vps"}
Done

References

1. How to do updating in MongoDB
2. $set update modifier
3. $inc update modifier
4. Java MongoDB APIs , DBCollection JavaDoc