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
- How to do updating in MongoDB
- $set update modifier
- $inc update modifier
- Java MongoDB APIs , DBCollection JavaDoc