spring boot mongodb 复制集、主从实现

1.上篇文章简单的介绍了Mongodb，和做了一个简单的SpringBoot - Mongodb单机实现，本文将介绍 SpringBoot mongodb replica set复制集读写分离的实现，主库：Primary ，从库：Secondary
复制主要用于备份、灾难恢复和读写分离，可以应对更多的读操作，当主库挂了可以从副本集中选一个主节点，更多作用请自行百度，怎么搭建复制集请参考我之前的 Mongodb安装与设置副本集二教程

2.spring boot 项目 Pom.xml中添加 spring-boot-starter-data-mongodb 包引用

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-data-mongodb</artifactId>
</dependency>

3.在application.properties中配置连接信息(使用yaml配置比较优雅，但我配置后未能实现连接)

spring.data.mongodb.primary.host=192.168.68.128
spring.data.mongodb.primary.port=27017
spring.data.mongodb.primary.database=test
spring.data.mongodb.primary.username=admin
spring.data.mongodb.primary.password=admin

spring.data.mongodb.secondary.host=192.168.68.129
spring.data.mongodb.secondary.port=27017
spring.data.mongodb.secondary.database=test
spring.data.mongodb.secondary.username=admin
spring.data.mongodb.secondary.password=admin

4.创建一个实体 User ,重写toString()方法，并在类上注解 @Document(collection = “user”) ，表名

@Document(collection = "user")
public class User {

    private Long mid;
    private String userName;
    private String passWord;

    @Override
    public String toString() {
        return "User{" +
                "mid=" + mid +
                ", userName='" + userName + '\'' +
                ", passWord='" + passWord + '\'' +
                '}';
    }
    //Getter Setter....
}

5.重点–创建一个抽象类 AbstractMongoConfig.class ，创建一个主库配置类 PrimaryMongoConfig.class 和一个从库配置类 SecondaryMongoConfig.class 继承抽象类，重写 getMongoTemplate() 方法，用户返回 MongoTemplate 对象

public abstract class AbstractMongoConfig {

    // Mongo DB Properties
    private String host, database, username, password;
    private int port;

    /*
     * Method that creates MongoDbFactory Common to both of the MongoDb
     * connections
     */
    public MongoDbFactory mongoDbFactory() throws Exception {
        String url = "mongodb://"+username+":"+password+"@"+host+":"+port+"/"+database;
        MongoClientURI uri = new MongoClientURI(url);
        return new SimpleMongoDbFactory(new MongoClient(uri),database);
    }

    /*
     * Factory method to create the MongoTemplate
     */
    abstract public MongoTemplate getMongoTemplate() throws Exception;

    //host, database, username, password Getter Setter....
}

@Configuration
//在application.properties中查找 spring.data.mongodb.primary 开头的配置信息
@ConfigurationProperties(prefix = "spring.data.mongodb.primary") 
public class PrimaryMongoConfig extends AbstractMongoConfig {

    /**
     * Implementation of the MongoTemplate factory method
     * @Bean gives a name (primaryMongoTemplate) to the created MongoTemplate instance
     * @Primary declares that if MongoTemplate is autowired without providing a specific name,
     * this is the instance which will be mapped by         default
     */
    @Primary
    @Override
    public @Bean(name = "primaryMongoTemplate") MongoTemplate getMongoTemplate() throws Exception {
        return new MongoTemplate(mongoDbFactory());
    }
}

@Configuration  
//在application.properties中查找 spring.data.mongodb.secondary开头的配置信息
@ConfigurationProperties(prefix = "spring.data.mongodb.secondary")  
public class SecondaryMongoConfig extends  AbstractMongoConfig {

    /**
     * Implementation of the MongoTemplate factory method
     * @Bean gives a name (primaryMongoTemplate) to the created MongoTemplate instance
     * Note that this method doesn't have @Primary
     */
    @Override
    public @Bean(name = "secondaryMongoTemplate") MongoTemplate getMongoTemplate() throws Exception {
        return new MongoTemplate(mongoDbFactory());
    }
}

6.UserDaoImpl类(省略了UserDao接口类)，使用配置类，获取 MongoTemplate

@Repository
public class UserDaoImpl implements UserDao{

    // Using MongoTemplate for primary database
    @Autowired
    @Qualifier(value = "primaryMongoTemplate") //和上面配置类中的Bean（name）的名字对应
    protected MongoTemplate primaryMongoTemplate;

    // Using mongoTemplate for secondary database
    @Autowired
    @Qualifier(value = "secondaryMongoTemplate")//和上面配置类中的Bean（name）的名字对应
    protected MongoTemplate secondaryMongoTemplate;

    //主库存
    @Override
    public void savePrimary(User user) {
        primaryMongoTemplate.save(user);
    }
    //从库存
    @Override
    public void saveSecondary(User user) {
        secondaryMongoTemplate.save(user);
    }
    //从库读
    @Override
    public User findUserByUserName(String userName) {
        Query query = new Query();
        query.addCriteria(Criteria.where("userName").is(userName));
        return secondaryMongoTemplate.findOne(query,User.class);
    }

}

7.测试，在测试类中运行如下代码：

//1.测试主库存
@Test
public void testSavePrimary() throws Exception {
    User pUser = new User();
    pUser.setMid(11L);
    pUser.setUserName("primary");
    pUser.setPassWord("123456");
    userDao.savePrimary(pUser);
}
//2.测试从库存
@Test
public void testSaveSecondary() throws Exception {
    User pSecond = new User();
    pSecond.setMid(12L);
    pSecond.setUserName("secondary");
    pSecond.setPassWord("123456");
    userDao.savePrimary(pSecond);
}
//3.从库读
@Test
public void testFindUser() throws Exception {
    User pSecond = userDao.findUserByUserName("secondary");
    System.out.println(pSecond.toString());
}

8.测试结果正确的保存和读取出来了，主库-从库保存的数据，从库读取的数据直接用toString()方法打印到控制台了：
这里写图片描述

实现读写分离还有另外一个方式：使用 lombok和spring-boot-autoconfigure 包，但我未实现出来，供大家参考和百度。

最后总结，此方式还不是太优雅，只能算是一个简单实现，遗留问题：要是有多个从库该怎么办，在配置文件中配置多个数据源？然后写多个从库配置类？调用的时候再写一个轮询方法，用来获取MongoTemplate？这些都是应该考虑的问题，现在的方式还不够优雅。。。有待研究与改进。希望那位大大指教指教

spring boot mongodb 复制集、主从实现

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