【IT168 专稿】在上一篇文章中，我们学习了Mongodb的安装和初步使用，在本文中，将学习如何使用Java去编程实现对Mongodb的操作。
HelloWorld程序
学习任何程序的第一步，都是编写HelloWorld程序，我们也不例外，看下如何通过Java编写一个HelloWorld的程序。
首先，要通过Java操作Mongodb，必须先下载Mongodb的Java驱动程序，可以在这里下载。
新建立一个Java工程，将下载的驱动程序放在库文件路径下，程序代码如下：
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 Hello world Example
*
*/
public class App {
public static void main(String[] args) {
try {
//实例化Mongo对象，连接27017端口
Mongo mongo = new Mongo("localhost", 27017);
//连接名为yourdb的数据库，假如数据库不存在的话，mongodb会自动建立
DB db = mongo.getDB("yourdb");
// Get collection from MongoDB, database named "yourDB"
//从Mongodb中获得名为yourColleection的数据集合，如果该数据集合不存在，Mongodb会为其新建立
DBCollection collection = db.getCollection("yourCollection");
// 使用BasicDBObject对象创建一个mongodb的document,并给予赋值。
BasicDBObject document = new BasicDBObject();
document.put("id", 1001);
document.put("msg", "hello world mongoDB in Java");
//将新建立的document保存到collection中去
collection.insert(document);
// 创建要查询的document
BasicDBObject searchQuery = new BasicDBObject();
searchQuery.put("id", 1001);
// 使用collection的find方法查找document
DBCursor cursor = collection.find(searchQuery);
//循环输出结果
while (cursor.hasNext()) {
System.out.println(cursor.next());
}
System.out.println("Done");
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (MongoException e) {
e.printStackTrace();
}
}
}
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 Hello world Example
*
*/
public class App {
public static void main(String[] args) {
try {
//实例化Mongo对象，连接27017端口
Mongo mongo = new Mongo("localhost", 27017);
//连接名为yourdb的数据库，假如数据库不存在的话，mongodb会自动建立
DB db = mongo.getDB("yourdb");
// Get collection from MongoDB, database named "yourDB"
//从Mongodb中获得名为yourColleection的数据集合，如果该数据集合不存在，Mongodb会为其新建立
DBCollection collection = db.getCollection("yourCollection");
// 使用BasicDBObject对象创建一个mongodb的document,并给予赋值。
BasicDBObject document = new BasicDBObject();
document.put("id", 1001);
document.put("msg", "hello world mongoDB in Java");
//将新建立的document保存到collection中去
collection.insert(document);
// 创建要查询的document
BasicDBObject searchQuery = new BasicDBObject();
searchQuery.put("id", 1001);
// 使用collection的find方法查找document
DBCursor cursor = collection.find(searchQuery);
//循环输出结果
while (cursor.hasNext()) {
System.out.println(cursor.next());
}
System.out.println("Done");
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (MongoException e) {
e.printStackTrace();
}
}
}
最后，输出的结果为：
{ "_id" : { "$oid" : "4dbe5596dceace565d229dc3"} ,
"id" : 1001 , "msg" : "hello world mongoDB in Java"}
Done
"id" : 1001 , "msg" : "hello world mongoDB in Java"}
Done
在上面的例子中，演示了使用Java对Mongodb操作的重要方法和步骤，首先通过创建Mongodb对象，传入构造函数的参数是Mongodb的数据库所在地址和端口，然后使用
getDB方法获得要连接的数据库名，使用getCollection获得数据集合的名，然后通过新建立BasicDBObject对象去建立document,最后通过collection的insert方法，将建立的document保存到数据库中去。而collection的find方法，则是用来在数据库中查找document。
从Mongodb中获得collection数据集
在Mongodb中，可以通过如下方法获得数据库中的collection:
DBCollection collection = db.getCollection("yourCollection");
如果你不知道collection的名称，可以使用db.getCollectionNames()获得集合，然后再遍历，如下：
DB db = mongo.getDB("yourdb");
Set collections = db.getCollectionNames();
for(String collectionName : collections){
System.out.println(collectionName);
}
Set collections = db.getCollectionNames();
for(String collectionName : collections){
System.out.println(collectionName);
}
完成的一个例子如下：
package com.mkyong.core;
import java.net.UnknownHostException;
import java.util.Set;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
/**
* Java : Get collection from MongoDB
*
*/
public class GetCollectionApp {
public static void main(String[] args) {
try {
Mongo mongo = new Mongo("localhost", 27017);
DB db = mongo.getDB("yourdb");
Set<String> collections = db.getCollectionNames();
for (String collectionName : collections) {
System.out.println(collectionName);
}
DBCollection collection = db.getCollection("yourCollection");
System.out.println(collection.toString());
System.out.println("Done");
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (MongoException e) {
e.printStackTrace();
}
}
}
import java.net.UnknownHostException;
import java.util.Set;
import com.mongodb.DB;
import com.mongodb.DBCollection;
import com.mongodb.Mongo;
import com.mongodb.MongoException;
/**
* Java : Get collection from MongoDB
*
*/
public class GetCollectionApp {
public static void main(String[] args) {
try {
Mongo mongo = new Mongo("localhost", 27017);
DB db = mongo.getDB("yourdb");
Set<String> collections = db.getCollectionNames();
for (String collectionName : collections) {
System.out.println(collectionName);
}
DBCollection collection = db.getCollection("yourCollection");
System.out.println(collection.toString());
System.out.println("Done");
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (MongoException e) {
e.printStackTrace();
}
}
}
Mongodb中如何插入数据
下面，讲解下如何使用4种方式，将JSON数据插入到Mongodb中去。首先我们准备JSON
格式的数据，如下：
{
"database" : "mkyongDB",
"table" : "hosting",
"detail" :
{
records : 99,
index : "vps_index1",
active : "true"
}
}
}
"database" : "mkyongDB",
"table" : "hosting",
"detail" :
{
records : 99,
index : "vps_index1",
active : "true"
}
}
}
我们希望用不同的方式，通过JAVA代码向Mongodb插入以上格式的JSON数据
第一种方法，是使用BasicDBObject，方法如下代码所示：
BasicDBObject document = new BasicDBObject();
document.put("database", "mkyongDB");
document.put("table", "hosting");
BasicDBObject documentDetail = new BasicDBObject();
documentDetail.put("records", "99");
documentDetail.put("index", "vps_index1");
documentDetail.put("active", "true");
document.put("detail", documentDetail);
collection.insert(document);
document.put("database", "mkyongDB");
document.put("table", "hosting");
BasicDBObject documentDetail = new BasicDBObject();
documentDetail.put("records", "99");
documentDetail.put("index", "vps_index1");
documentDetail.put("active", "true");
document.put("detail", documentDetail);
collection.insert(document);
第二种方法是使用BasicDBObjectBuilder对象，如下代码所示：
BasicDBObjectBuilder documentBuilder = BasicDBObjectBuilder.start()
.add("database", "mkyongDB")
.add("table", "hosting");
BasicDBObjectBuilder documentBuilderDetail = BasicDBObjectBuilder.start()
.add("records", "99")
.add("index", "vps_index1")
.add("active", "true");
documentBuilder.add("detail", documentBuilderDetail.get());
collection.insert(documentBuilder.get());
.add("database", "mkyongDB")
.add("table", "hosting");
BasicDBObjectBuilder documentBuilderDetail = BasicDBObjectBuilder.start()
.add("records", "99")
.add("index", "vps_index1")
.add("active", "true");
documentBuilder.add("detail", documentBuilderDetail.get());
collection.insert(documentBuilder.get());
第三种方法是使用Map对象，代码如下：
Map documentMap =new HashMap();
documentMap.put("database", "mkyongDB");
documentMap.put("table", "hosting");
Map documentMapDetail =new HashMap();
documentMapDetail.put("records", "99");
documentMapDetail.put("index", "vps_index1");
documentMapDetail.put("active", "true");
documentMap.put("detail", documentMapDetail);
collection.insert(new BasicDBObject(documentMap));
documentMap.put("database", "mkyongDB");
documentMap.put("table", "hosting");
Map documentMapDetail =new HashMap();
documentMapDetail.put("records", "99");
documentMapDetail.put("index", "vps_index1");
documentMapDetail.put("active", "true");
documentMap.put("detail", documentMapDetail);
collection.insert(new BasicDBObject(documentMap));
第四种方法，也就是最简单的，即直接插入JSON格式数据
String json ="{'database' : 'mkyongDB','table' : 'hosting',"+
"'detail' : {'records' : 99, 'index' : 'vps_index1', 'active' : 'true'}}}";
DBObject dbObject =(DBObject)JSON.parse(json);
collection.insert(dbObject);
"'detail' : {'records' : 99, 'index' : 'vps_index1', 'active' : 'true'}}}";
DBObject dbObject =(DBObject)JSON.parse(json);
collection.insert(dbObject);
这里使用了JSON的parse方法，将解析后的JSON字符串转变为DBObject对象后再直接插入到collection中去。
完整的代码如下所示：
packagecom.mkyong.core;
importjava.net.UnknownHostException;
importjava.util.HashMap;
importjava.util.Map;
importcom.mongodb.BasicDBObject;
importcom.mongodb.BasicDBObjectBuilder;
importcom.mongodb.DB;
importcom.mongodb.DBCollection;
importcom.mongodb.DBCursor;
importcom.mongodb.DBObject;
importcom.mongodb.Mongo;
importcom.mongodb.MongoException;
importcom.mongodb.util.JSON;
/**
* Java MongoDB : Insert a Document
*
*/
publicclass InsertDocumentApp {
publicstaticvoid main(String[] args){
try{
Mongo mongo =new Mongo("localhost", 27017);
DB db = mongo.getDB("yourdb");
// get a single collection
DBCollection collection = db.getCollection("dummyColl");
// BasicDBObject example
System.out.println("BasicDBObject example...");
BasicDBObject document =new BasicDBObject();
document.put("database", "mkyongDB");
document.put("table", "hosting");
BasicDBObject documentDetail =new BasicDBObject();
documentDetail.put("records", "99");
documentDetail.put("index", "vps_index1");
documentDetail.put("active", "true");
document.put("detail", documentDetail);
collection.insert(document);
DBCursor cursorDoc = collection.find();
while(cursorDoc.hasNext()){
System.out.println(cursorDoc.next());
}
collection.remove(new BasicDBObject());
// BasicDBObjectBuilder example
System.out.println("BasicDBObjectBuilder example...");
BasicDBObjectBuilder documentBuilder = BasicDBObjectBuilder.start()
.add("database", "mkyongDB")
.add("table", "hosting");
BasicDBObjectBuilder documentBuilderDetail = BasicDBObjectBuilder.start()
.add("records", "99")
.add("index", "vps_index1")
.add("active", "true");
documentBuilder.add("detail", documentBuilderDetail.get());
collection.insert(documentBuilder.get());
DBCursor cursorDocBuilder = collection.find();
while(cursorDocBuilder.hasNext()){
System.out.println(cursorDocBuilder.next());
}
collection.remove(new BasicDBObject());
// Map example
System.out.println("Map example...");
Map documentMap =new HashMap();
documentMap.put("database", "mkyongDB");
documentMap.put("table", "hosting");
Map documentMapDetail =new HashMap();
documentMapDetail.put("records", "99");
documentMapDetail.put("index", "vps_index1");
documentMapDetail.put("active", "true");
documentMap.put("detail", documentMapDetail);
collection.insert(new BasicDBObject(documentMap));
DBCursor cursorDocMap = collection.find();
while(cursorDocMap.hasNext()){
System.out.println(cursorDocMap.next());
}
collection.remove(new BasicDBObject());
// JSON parse example
System.out.println("JSON parse example...");
String json ="{'database' : 'mkyongDB','table' : 'hosting',"+
"'detail' : {'records' : 99, 'index' : 'vps_index1', 'active' : 'true'}}}";
DBObject dbObject =(DBObject)JSON.parse(json);
collection.insert(dbObject);
DBCursor cursorDocJSON = collection.find();
while(cursorDocJSON.hasNext()){
System.out.println(cursorDocJSON.next());
}
collection.remove(new BasicDBObject());
}catch(UnknownHostException e){
e.printStackTrace();
}catch(MongoException e){
e.printStackTrace();
}
}
}
importjava.net.UnknownHostException;
importjava.util.HashMap;
importjava.util.Map;
importcom.mongodb.BasicDBObject;
importcom.mongodb.BasicDBObjectBuilder;
importcom.mongodb.DB;
importcom.mongodb.DBCollection;
importcom.mongodb.DBCursor;
importcom.mongodb.DBObject;
importcom.mongodb.Mongo;
importcom.mongodb.MongoException;
importcom.mongodb.util.JSON;
/**
* Java MongoDB : Insert a Document
*
*/
publicclass InsertDocumentApp {
publicstaticvoid main(String[] args){
try{
Mongo mongo =new Mongo("localhost", 27017);
DB db = mongo.getDB("yourdb");
// get a single collection
DBCollection collection = db.getCollection("dummyColl");
// BasicDBObject example
System.out.println("BasicDBObject example...");
BasicDBObject document =new BasicDBObject();
document.put("database", "mkyongDB");
document.put("table", "hosting");
BasicDBObject documentDetail =new BasicDBObject();
documentDetail.put("records", "99");
documentDetail.put("index", "vps_index1");
documentDetail.put("active", "true");
document.put("detail", documentDetail);
collection.insert(document);
DBCursor cursorDoc = collection.find();
while(cursorDoc.hasNext()){
System.out.println(cursorDoc.next());
}
collection.remove(new BasicDBObject());
// BasicDBObjectBuilder example
System.out.println("BasicDBObjectBuilder example...");
BasicDBObjectBuilder documentBuilder = BasicDBObjectBuilder.start()
.add("database", "mkyongDB")
.add("table", "hosting");
BasicDBObjectBuilder documentBuilderDetail = BasicDBObjectBuilder.start()
.add("records", "99")
.add("index", "vps_index1")
.add("active", "true");
documentBuilder.add("detail", documentBuilderDetail.get());
collection.insert(documentBuilder.get());
DBCursor cursorDocBuilder = collection.find();
while(cursorDocBuilder.hasNext()){
System.out.println(cursorDocBuilder.next());
}
collection.remove(new BasicDBObject());
// Map example
System.out.println("Map example...");
Map documentMap =new HashMap();
documentMap.put("database", "mkyongDB");
documentMap.put("table", "hosting");
Map documentMapDetail =new HashMap();
documentMapDetail.put("records", "99");
documentMapDetail.put("index", "vps_index1");
documentMapDetail.put("active", "true");
documentMap.put("detail", documentMapDetail);
collection.insert(new BasicDBObject(documentMap));
DBCursor cursorDocMap = collection.find();
while(cursorDocMap.hasNext()){
System.out.println(cursorDocMap.next());
}
collection.remove(new BasicDBObject());
// JSON parse example
System.out.println("JSON parse example...");
String json ="{'database' : 'mkyongDB','table' : 'hosting',"+
"'detail' : {'records' : 99, 'index' : 'vps_index1', 'active' : 'true'}}}";
DBObject dbObject =(DBObject)JSON.parse(json);
collection.insert(dbObject);
DBCursor cursorDocJSON = collection.find();
while(cursorDocJSON.hasNext()){
System.out.println(cursorDocJSON.next());
}
collection.remove(new BasicDBObject());
}catch(UnknownHostException e){
e.printStackTrace();
}catch(MongoException e){
e.printStackTrace();
}
}
}
更新Document
假设如下的JSON格式的数据已经保存到Mongodb中去了，现在要更新相关的数据。
{"_id" : {"$oid" : "x"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{"_id" : {"$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{"_id" : {"$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
{"_id" : {"$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{"_id" : {"$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
假设现在要将hosting中值为hostB的进行更新，则可以使用如下的方法：
BasicDBObject newDocument =new BasicDBObject();
newDocument.put("hosting", "hostB");
newDocument.put("type", "shared host");
newDocument.put("clients", 111);
collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument);
newDocument.put("hosting", "hostB");
newDocument.put("type", "shared host");
newDocument.put("clients", 111);
collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument);
可以看到，这里依然使用了BasicDBObject对象，并为其赋值了新的值后，然后使用collection的update方法，即可更新该对象。
更新后的输出如下：
{"_id" : {"$oid" : "x"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{"_id" : {"$oid" : "x"} , "hosting" : "hostB" , "type" : "shared host" , "clients" : 111}
{"_id" : {"$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
{"_id" : {"$oid" : "x"} , "hosting" : "hostB" , "type" : "shared host" , "clients" : 111}
{"_id" : {"$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
另外，还可以使用mongodb中的$inc修饰符号去对某个值进行更新，比如，要将hosting值为hostB的document的clients的值得更新为199(即100+99=199)，可以这样：
BasicDBObject newDocument =new BasicDBObject().append("$inc",
new BasicDBObject().append("clients", 99));
collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument);
new BasicDBObject().append("clients", 99));
collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument);
则输出如下：
{"_id" : {"$oid" : "x"} , "hosting" : "hostA" , "type" : "vps" , "clients" : 1000}
{"_id" : {"$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 199}
{"_id" : {"$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
{"_id" : {"$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 199}
{"_id" : {"$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
接下来，讲解$set修饰符的使用。比如要把hosting中值为hostA的document中的
type的值进行修改，则可以如下实现：
BasicDBObject newDocument3 =new BasicDBObject().append("$set",
new BasicDBObject().append("type", "dedicated server"));
collection.update(new BasicDBObject().append("hosting", "hostA"), newDocument3);
new BasicDBObject().append("type", "dedicated server"));
collection.update(new BasicDBObject().append("hosting", "hostA"), newDocument3);
则输出如下，把type的值从vps改为dedicated server:
{"_id" : {"$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{"_id" : {"$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
{"_id" : {"$oid" : "x"} , "hosting" : "hostA" , "clients" : 1000 , "type" : "dedicated server"}
{"_id" : {"$oid" : "x"} , "hosting" : "hostC" , "type" : "vps" , "clients" : 900}
{"_id" : {"$oid" : "x"} , "hosting" : "hostA" , "clients" : 1000 , "type" : "dedicated server"}
要注意的是，如果不使用$set的修饰符，而只是如下代码：
BasicDBObject newDocument3 =new BasicDBObject().append("type", "dedicated server");
collection.update(new BasicDBObject().append("hosting", "hostA"), newDocument3);
collection.update(new BasicDBObject().append("hosting", "hostA"), newDocument3);
则会将所有的三个document的type类型都改为dedicated server了，因此要使用$set以更新特定的document的特定的值。
如果要更新多个document中相同的值，可以使用$multi，比如，要把所有vps为type的document,将它们的clients的值更新为888，可以如下实现：
BasicDBObject updateQuery =new BasicDBObject().append("$set",
new BasicDBObject().append("clients", "888"));
collection.update(new BasicDBObject().append("type", "vps"), updateQuery, false, true);
new BasicDBObject().append("clients", "888"));
collection.update(new BasicDBObject().append("type", "vps"), updateQuery, false, true);
输出如下：
{"_id" : {"$oid" : "x"} , "hosting" : "hostA" , "clients" : "888" , "type" : "vps"}
{"_id" : {"$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{"_id" : {"$oid" : "x"} , "hosting" : "hostC" , "clients" : "888" , "type" : "vps"}
{"_id" : {"$oid" : "x"} , "hosting" : "hostB" , "type" : "dedicated server" , "clients" : 100}
{"_id" : {"$oid" : "x"} , "hosting" : "hostC" , "clients" : "888" , "type" : "vps"}
最后，还是给出更新document的完整例子：
package com.liao;
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;
publicclass UpdateDocumentApp {
publicstaticvoid printAllDocuments(DBCollection collection){
DBCursor cursor = collection.find();
while (cursor.hasNext()) {
System.out.println(cursor.next());
}
}
publicstaticvoid removeAllDocuments(DBCollection collection){
collection.remove(new BasicDBObject());
}
publicstaticvoid 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);
}
publicstaticvoid main(String[] args) {
try {
Mongo mongo = new Mongo("localhost", 27017);
DB db = mongo.getDB("yourdb");
DBCollection collection = db.getCollection("dummyColl");
System.out.println("Testing 1...");
insertDummyDocuments(collection);
//find hosting = hostB, and update it with new document
BasicDBObject newDocument = new BasicDBObject();
newDocument.put("hosting", "hostB");
newDocument.put("type", "shared host");
newDocument.put("clients", 111);
collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument);
printAllDocuments(collection);
removeAllDocuments(collection);
System.out.println("Testing 2...");
insertDummyDocuments(collection);
BasicDBObject newDocument2 = new BasicDBObject().append("$inc",
new BasicDBObject().append("clients", 99));
collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument2);
printAllDocuments(collection);
removeAllDocuments(collection);
System.out.println("Testing 3...");
insertDummyDocuments(collection);
BasicDBObject newDocument3 = new BasicDBObject().append("$set",
new BasicDBObject().append("type", "dedicated server"));
collection.update(new BasicDBObject().append("hosting", "hostA"), newDocument3);
printAllDocuments(collection);
removeAllDocuments(collection);
System.out.println("Testing 4...");
insertDummyDocuments(collection);
BasicDBObject updateQuery = new BasicDBObject().append("$set",
new BasicDBObject().append("clients", "888"));
collection.update(
new BasicDBObject().append("type", "vps"), updateQuery, false, true);
printAllDocuments(collection);
removeAllDocuments(collection);
System.out.println("Done");
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (MongoException e) {
e.printStackTrace();
}
}
}
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;
publicclass UpdateDocumentApp {
publicstaticvoid printAllDocuments(DBCollection collection){
DBCursor cursor = collection.find();
while (cursor.hasNext()) {
System.out.println(cursor.next());
}
}
publicstaticvoid removeAllDocuments(DBCollection collection){
collection.remove(new BasicDBObject());
}
publicstaticvoid 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);
}
publicstaticvoid main(String[] args) {
try {
Mongo mongo = new Mongo("localhost", 27017);
DB db = mongo.getDB("yourdb");
DBCollection collection = db.getCollection("dummyColl");
System.out.println("Testing 1...");
insertDummyDocuments(collection);
//find hosting = hostB, and update it with new document
BasicDBObject newDocument = new BasicDBObject();
newDocument.put("hosting", "hostB");
newDocument.put("type", "shared host");
newDocument.put("clients", 111);
collection.update(new BasicDBObject().append("hosting", "hostB"), newDocument);
printAllDocuments(collection);
removeAllDocuments(collection);
System.out.println("Testing 2...");
insertDummyDocuments(collection);
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("Testing 3...");
insertDummyDocuments(collection);
BasicDBObject newDocument3 = new BasicDBObject().append("$set",
new BasicDBObject().append("type", "dedicated server"));
collection.update(new BasicDBObject().append("hosting", "hostA"), newDocument3);
printAllDocuments(collection);
removeAllDocuments(collection);
System.out.println("Testing 4...");
insertDummyDocuments(collection);
BasicDBObject updateQuery = new BasicDBObject().append("$set",
new BasicDBObject().append("clients", "888"));
collection.update(
new BasicDBObject().append("type", "vps"), updateQuery, false, true);
printAllDocuments(collection);
removeAllDocuments(collection);
System.out.println("Done");
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (MongoException e) {
e.printStackTrace();
}
}
}
查询Document
下面学习如何查询document,先用下面的代码往数据库中插入1-10数字：
for(int i=1; i <=10; i++){
collection.insert(new BasicDBObject().append("number", i));
}
collection.insert(new BasicDBObject().append("number", i));
}
接下来，看下如下的例子：
1) 获得数据库中的第一个document:
DBObject doc = collection.findOne();
System.out.println(dbObject);
System.out.println(dbObject);
输出为：
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80bd"} , "number" : 1}
2)获得document的集合
DBCursor cursor = collection.find();
while(cursor.hasNext()){
System.out.println(cursor.next());
}
while(cursor.hasNext()){
System.out.println(cursor.next());
}
这里，使用collection.find()方法，获得当前数据库中所有的documents对象集合
然后通过对DBCursor对象集合的遍历，即可输出当前所有documents。输出如下：
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80bd"} , "number" : 1}
//..........中间部分省略，为2到9的输出
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c6"} , "number" : 10}
//..........中间部分省略，为2到9的输出
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c6"} , "number" : 10}
3) 获取指定的document
比如要获得number=5的document对象内容，可以使用collection的find方法即可，如下：
BasicDBObject query =new BasicDBObject();
query.put("number", 5);
DBCursor cursor = collection.find(query);
while(cursor.hasNext()){
System.out.println(cursor.next());
}
query.put("number", 5);
DBCursor cursor = collection.find(query);
while(cursor.hasNext()){
System.out.println(cursor.next());
}
即输出：
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c1"} , "number" : 5}
4) 使用in操作符号
在mongodb中，也可以使用in操作符，比如要获得number=9和number=10的document对象，可以如下操作：
BasicDBObject query =new BasicDBObject();
List list =new ArrayList();
list.add(9);
list.add(10);
query.put("number", new BasicDBObject("$in", list));
DBCursor cursor = collection.find(query);
while(cursor.hasNext()){
System.out.println(cursor.next());
}
List list =new ArrayList();
list.add(9);
list.add(10);
query.put("number", new BasicDBObject("$in", list));
DBCursor cursor = collection.find(query);
while(cursor.hasNext()){
System.out.println(cursor.next());
}
这里使用了一个List，并将list传入到BasicDBObject的构造函数中，并使用了in操作符号，输出如下：
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c5"} , "number" : 9}
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c6"} , "number" : 10}
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c6"} , "number" : 10}
5) 使用>,<等比较符号
在mongodb中，也可以使用比如>,<等数量比较符号，比如要输出number>5的document集合，则使用“$gt”即可，同理，小于关系则使用$lt，例子如下：
BasicDBObject query =new BasicDBObject();
query.put("number", new BasicDBObject("$gt", 5));
DBCursor cursor = collection.find(query);
while(cursor.hasNext()){
System.out.println(cursor.next());
}
query.put("number", new BasicDBObject("$gt", 5));
DBCursor cursor = collection.find(query);
while(cursor.hasNext()){
System.out.println(cursor.next());
}
输出如下：
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c2"} , "number" : 6}
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c3"} , "number" : 7}
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c4"} , "number" : 8}
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c5"} , "number" : 9}
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c6"} , "number" : 10}
也可以多个比较符号一起使用，比如要输出number>5和number<8的document,则如下：
BasicDBObject query =new BasicDBObject();
query.put("number", new BasicDBObject("$gt", 5).append("$lt", 8));
DBCursor cursor = collection.find(query);
while(cursor.hasNext()){
System.out.println(cursor.next());
}
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c3"} , "number" : 7}
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c4"} , "number" : 8}
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c5"} , "number" : 9}
{"_id" : {"$oid" : "4dc7f7b7bd0fb9a86c6c80c6"} , "number" : 10}
也可以多个比较符号一起使用，比如要输出number>5和number<8的document,则如下：
BasicDBObject query =new BasicDBObject();
query.put("number", new BasicDBObject("$gt", 5).append("$lt", 8));
DBCursor cursor = collection.find(query);
while(cursor.hasNext()){
System.out.println(cursor.next());
}
同样，如果是不等于的关系的话，可以使用$ne操作符，如下：
BasicDBObject query5 =new BasicDBObject();
query5.put("number", new BasicDBObject("$ne", 8));
DBCursor cursor6 = collection.find(query5);
while(cursor6.hasNext()){
System.out.println(cursor6.next());
}
query5.put("number", new BasicDBObject("$ne", 8));
DBCursor cursor6 = collection.find(query5);
while(cursor6.hasNext()){
System.out.println(cursor6.next());
}
以上输出number=8之外的所有document。
删除document
下面我们学习如何删除document，依然以上面的已插入的1-10的documents集合为例说明：
1) 删除第一个document
DBObject doc = collection.findOne();
collection.remove(doc);
collection.remove(doc);
2) 删除指定的document
比如删除number=2的document,如下方法：
BasicDBObject document =new BasicDBObject();
document.put("number", 2);
collection.remove(document);
document.put("number", 2);
collection.remove(document);
要注意的是，如下的方法将只会删除number=3的document。
BasicDBObject document =new BasicDBObject();
document.put("number", 2);
document.put("number", 3);
collection.remove(document);
document.put("number", 2);
document.put("number", 3);
collection.remove(document);
3) 使用in 操作符号指定删除document
下面的例子将同时删除number=4和number=5的document，使用的是in操作符
BasicDBObject query2 =new BasicDBObject();
List list =new ArrayList();
list.add(4);
list.add(5);
query2.put("number", new BasicDBObject("$in", list));
collection.remove(query2);
List list =new ArrayList();
list.add(4);
list.add(5);
query2.put("number", new BasicDBObject("$in", list));
collection.remove(query2);
4) 使用“$gt”删除大于某个值的document
BasicDBObject query =new BasicDBObject();
query.put("number", new BasicDBObject("$gt", 9));
collection.remove(query);
query.put("number", new BasicDBObject("$gt", 9));
collection.remove(query);
以上会删除number=10的document。
5) 删除所有的document
DBCursor cursor = collection.find();
while(cursor.hasNext()){
collection.remove(cursor.next());
}
while(cursor.hasNext()){
collection.remove(cursor.next());
}
保存图片到Mongodb
下面将讲解如何使用Java MongoDB GridFS API去保存图片等二进制文件到Monodb，关于Java MongoDB GridFS API的详细论述，请参考http://www.mongodb.org/display/DOCS/GridFS+Specification
1)保存图片
代码段如下：
String newFileName ="mkyong-java-image";
File imageFile =newFile("c:\\JavaWebHosting.png");
GridFS gfsPhoto =new GridFS(db, "photo");
GridFSInputFile gfsFile = gfsPhoto.createFile(imageFile);
gfsFile.setFilename(newFileName);
gfsFile.save();
File imageFile =newFile("c:\\JavaWebHosting.png");
GridFS gfsPhoto =new GridFS(db, "photo");
GridFSInputFile gfsFile = gfsPhoto.createFile(imageFile);
gfsFile.setFilename(newFileName);
gfsFile.save();
这里，将c盘下的JavaWebHosting.png保存到mongodb中去，并命名为mkyong-java-image。
2) 读取图片信息
代码段如下
String newFileName ="mkyong-java-image";
GridFS gfsPhoto =new GridFS(db, "photo");
GridFSDBFile imageForOutput = gfsPhoto.findOne(newFileName);
System.out.println(imageForOutput);
GridFS gfsPhoto =new GridFS(db, "photo");
GridFSDBFile imageForOutput = gfsPhoto.findOne(newFileName);
System.out.println(imageForOutput);
将会输出JSON格式的结果;
{
"_id" :
{
"$oid" : "4dc9511a14a7d017fee35746"
} ,
"chunkSize" : 262144 ,
"length" : 22672 ,
"md5" : "1462a6cfa27669af1d8d21c2d7dd1f8b" ,
"filename" : "mkyong-java-image" ,
"contentType" : null ,
"uploadDate" :
{
"$date" : "2011-05-10T14:52:10Z"
} ,
"aliases" : null
}
"_id" :
{
"$oid" : "4dc9511a14a7d017fee35746"
} ,
"chunkSize" : 262144 ,
"length" : 22672 ,
"md5" : "1462a6cfa27669af1d8d21c2d7dd1f8b" ,
"filename" : "mkyong-java-image" ,
"contentType" : null ,
"uploadDate" :
{
"$date" : "2011-05-10T14:52:10Z"
} ,
"aliases" : null
}
可以看到，输出的是文件的属性相关信息。
3) 输出已保存的所有图片
下面代码段，输出所有保存在photo命名空间下的图片信息：
GridFS gfsPhoto =new GridFS(db, "photo");
DBCursor cursor = gfsPhoto.getFileList();
while(cursor.hasNext()){
System.out.println(cursor.next());
}
DBCursor cursor = gfsPhoto.getFileList();
while(cursor.hasNext()){
System.out.println(cursor.next());
}
4) 从数据库中读取一张图片并另存
下面的代码段，从数据库中读取一张图片并另存为另外一张图片到磁盘中
String newFileName ="mkyong-java-image";
GridFS gfsPhoto =new GridFS(db, "photo");
GridFSDBFile imageForOutput = gfsPhoto.findOne(newFileName);
imageForOutput.writeTo("c:\\JavaWebHostingNew.png");
GridFS gfsPhoto =new GridFS(db, "photo");
GridFSDBFile imageForOutput = gfsPhoto.findOne(newFileName);
imageForOutput.writeTo("c:\\JavaWebHostingNew.png");
5) 删除图片
String newFileName ="mkyong-java-image";
GridFS gfsPhoto =new GridFS(db, "photo");
gfsPhoto.remove(gfsPhoto.findOne(newFileName));
GridFS gfsPhoto =new GridFS(db, "photo");
gfsPhoto.remove(gfsPhoto.findOne(newFileName));
如何将JSON数据格式转化为DBObject格式
在mongodb中，可以使用com.mongodb.util.JSON类，将JSON格式的字符串转变为DBObject对象。MongoDB for JAVA驱动中提供了用于向数据库中存储普通对象的接口DBObject，当一个文档从MongoDB中取出时，它会自动把文档转换成DBObject接口类型，要将它实例化为需要的对象。比如：
{
'name' : 'mkyong',
'age' : 30
}
'name' : 'mkyong',
'age' : 30
}
这样的JSON格式字符串，转换方法为：
DBObject dbObject =(DBObject) JSON.parse("{'name':'mkyong', 'age':30}");
完整的代码如下：
packagecom.mkyong.core;
importjava.net.UnknownHostException;
importcom.mongodb.DB;
importcom.mongodb.DBCollection;
importcom.mongodb.DBCursor;
importcom.mongodb.DBObject;
importcom.mongodb.Mongo;
importcom.mongodb.MongoException;
importcom.mongodb.util.JSON;
/**
* Java MongoDB : Convert JSON data to DBObject
*
*/
publicclass App {
publicstaticvoid main(String[] args){
try{
Mongo mongo =new Mongo("localhost", 27017);
DB db = mongo.getDB("yourdb");
DBCollection collection = db.getCollection("dummyColl");
DBObject dbObject =(DBObject) JSON
.parse("{'name':'mkyong', 'age':30}");
collection.insert(dbObject);
DBCursor cursorDoc = collection.find();
while(cursorDoc.hasNext()){
System.out.println(cursorDoc.next());
}
System.out.println("Done");
}catch(UnknownHostException e){
e.printStackTrace();
}catch(MongoException e){
e.printStackTrace();
}
}
}
importjava.net.UnknownHostException;
importcom.mongodb.DB;
importcom.mongodb.DBCollection;
importcom.mongodb.DBCursor;
importcom.mongodb.DBObject;
importcom.mongodb.Mongo;
importcom.mongodb.MongoException;
importcom.mongodb.util.JSON;
/**
* Java MongoDB : Convert JSON data to DBObject
*
*/
publicclass App {
publicstaticvoid main(String[] args){
try{
Mongo mongo =new Mongo("localhost", 27017);
DB db = mongo.getDB("yourdb");
DBCollection collection = db.getCollection("dummyColl");
DBObject dbObject =(DBObject) JSON
.parse("{'name':'mkyong', 'age':30}");
collection.insert(dbObject);
DBCursor cursorDoc = collection.find();
while(cursorDoc.hasNext()){
System.out.println(cursorDoc.next());
}
System.out.println("Done");
}catch(UnknownHostException e){
e.printStackTrace();
}catch(MongoException e){
e.printStackTrace();
}
}
}
则输出为：
{"_id" : {"$oid" : "4dc9ebb5237f275c2fe4959f"} , "name" : "mkyong" , "age" : 30}
Done
可以看到，将JSON格式的数据类型直接转换为mongodb中的文档类型并输出。
小结：
本文学习了如何使用Mongodb for JAVA驱动，对mongodb进行日常的数据库操作，比如增加，删除和修改，下一篇教程中，将指导学习Spring对mongodb的操作。
