什么是Spring Data Mongo
Spring Data MongoDB项目对访问MongoDB的Java客户端API进行了封装，这种封装类似于Spring封装Hibernate和JDBC而提供的HibernateTemplate和JDBCTemplate，主要能力包括
1. 封装客户端跟MongoDB的链接管理
2. 文档-对象映射，通过注解:@Document(collection="collectionName")
3.对模版式的代码，进行了封装，类似于JDBCTemplate和HibernateTemplate
Spring Data Mongo在Spring中的基本配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:mongo="http://www.springframework.org/schema/data/mongo"
xsi:schemaLocation="http://www.springframework.org/schema/data/mongo
http://www.springframework.org/schema/data/mongo/spring-mongo-1.0.xsd
http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">
<mongo:mongo replica-set="localhost:27018,localhost:27017,localhost:27019">
<mongo:options connections-per-host="200"
threads-allowed-to-block-for-connection-multiplier="100"
connect-timeout="1000"
max-wait-time="1500"
auto-connect-retry="true"
socket-keep-alive="true"
socket-timeout="1500"
slave-ok="true"
write-number="1"
write-timeout="0"
write-fsync="true"/>
</mongo:mongo>
<mongo:db-factory dbname="foolbar" username="" password="" mongo-ref="mongo"/>
<bean id="mongoTemplate" class="org.springframework.data.mongodb.core.MongoTemplate">
<constructor-arg name="mongoDbFactory" ref="mongoDbFactory"/>
</bean>
</beans>
说明：
1.其中的mongoTemplate是客户端操作MongoDB的主要类，它包含了增删改查功能以及其它一些操作，这些操作在以后的篇幅中会讲到
2.replica-set是副本集集群的MongoDB服务器的链接地址，以逗号分开，如果仅有一台服务器，使用host="localhost:27017”或者replica-set="localhost:27017"都可以，
3.mongo:options定义了链接属性和读写相关属性，以后再来完善这部分
Document和Collection注解
package com.tom.user.model;
import org.bson.types.ObjectId;
import org.springframework.data.annotation.Id;
import org.springframework.data.mongodb.core.mapping.Document;
@Document(collection = "users")
public class User {
@Id
private ObjectId userId;
private String name;
private String passwd;
public ObjectId getUserId() {
return userId;
}
public void setUserId(ObjectId userId) {
this.userId = userId;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPasswd() {
return passwd;
}
public void setPasswd(String passwd) {
this.passwd = passwd;
}
}
上面的代码定义了一个类似于Hibernate实体Bean的POJO，在Hibernate它可以和数据库的一个表建立映射关系，但是在MongoDB中，一个集合中的文档的Field是任意的，因此POJO必须映射到文档一级(@Document)，同时注解中指明这个文档属于哪个集合(一个文档只能属于一个集合)。当使用MongoDBTemplate对POJO进行操作时，可以根据POJO的类型得到它要往那个集合中写文档
MongoDBTemplate简单CRUD操作
package com.tom.user.storage;
import com.tom.user.model.User;
import org.junit.Assert;
import org.junit.Before;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.data.mongodb.core.MongoTemplate;
import org.springframework.data.mongodb.core.query.Criteria;
import org.springframework.data.mongodb.core.query.Query;
import org.springframework.data.mongodb.core.query.Update;
import java.util.List;
/*
http://www.tuicool.com/articles/EFnyye
http://www.mkyong.com/mongodb/spring-data-mongodb-hello-world-example/
*/
public class UserMongoDBStorageServiceTest2 {
private ApplicationContext cxt = null;
@Before
public void setup() {
cxt = new ClassPathXmlApplicationContext("applicationContext.xml");
}
private void create() {
drop();
MongoTemplate template = cxt.getBean("mongoTemplate", MongoTemplate.class);
User user = new User();
user.setName("abc");
user.setPasswd("def");
template.insert(user);
}
public void query() {
Query query = new Query(new Criteria("name").is("abc"));
MongoTemplate template = cxt.getBean("mongoTemplate", MongoTemplate.class);
List<User> users = template.find(query, User.class);
Assert.assertEquals(1, users.size());
User user = users.get(0);
Assert.assertEquals("abc", user.getName());
Assert.assertEquals("def", user.getPasswd());
}
public void update() {
Query query = new Query(new Criteria("name").is("abc"));
MongoTemplate template = cxt.getBean("mongoTemplate", MongoTemplate.class);
List<User> users = template.find(query, User.class);
Assert.assertEquals(1, users.size());
User user = users.get(0);
user.setPasswd("def-updated");
Update update = new Update();
update.set("passwd",user.getPasswd());
template.updateFirst(query, update, User.class);
Assert.assertEquals("abc", user.getName());
}
public void queryUpdate() {
MongoTemplate template = cxt.getBean("mongoTemplate", MongoTemplate.class);
List<User> users = template.findAll(User.class);
Assert.assertEquals(1, users.size());
User user = users.get(0);
Assert.assertEquals("abc", user.getName());
Assert.assertEquals("def-updated",user.getPasswd());
}
public void drop() {
MongoTemplate template = cxt.getBean("mongoTemplate", MongoTemplate.class);
template.dropCollection(User.class);
}
@org.junit.Test
public void testCRUD() {
create();
query();
update();
queryUpdate();
drop();
}
}
只对Update操作做下说明：
public void update() {
Query query = new Query(new Criteria("name").is("abc"));
MongoTemplate template = cxt.getBean("mongoTemplate", MongoTemplate.class);
List<User> users = template.find(query, User.class);
Assert.assertEquals(1, users.size());
User user = users.get(0);
user.setPasswd("def-updated");
Update update = new Update();
update.set("passwd",user.getPasswd());
template.updateFirst(query, update, User.class);
Assert.assertEquals("abc", user.getName());
}
User两个字段name和passwd，Update中只通过Update.set方法对passwd进行了更改，那么name这个属性在更新操作完成后是从文档中被删除了还是保留下来了？答案是保留下来了，并且值保持不变，这就为更新操作提供了很大的便利性，要改什么就在Update中指定什么，