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使用Java操作MongoDB

时间:2021-07-01 10:21:17 帮助过:30人阅读

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

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();

}

}

}

  最后,输出的结果为:

{?”_id”?: {?”$oid”?:?”4dbe5596dceace565d229dc3″} ,?

“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);

}

  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?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”

}

}

}

  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);

  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());

  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));

  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);

  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();

}

}

}

  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}

?  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);

?  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}

?  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);

?  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}

?  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);

?  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”}

?  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);

?  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);

  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”}

  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();

}

}

}

  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));



}

?  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);

?  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());

}

?  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}

?  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());

}

?  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());

}

?  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}

  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());

}

?  输出如下:

  {“_id”?: {“$oid”?:?”4dc7f7b7bd0fb9a86c6c80c2″} ,?”number”?:?6}

{“_id”?: {“$oid”?:?”4dc7f7b7bd0fb9a86c6c80c3″} ,?”number”?:?7}

{“_id”?: {“$oid”?:?”4dc7f7b7bd0fb9a86c6c80c4″} ,?”number”?:?8}

{“_id

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