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