Spring Boot (five) to achieve multi data source configuration and source code analysis from entry to the master

Multi data source configuration in the project are relatively common software development needs, Spring and Spring Boot in this regard has the appropriate solution for your reference. In Spring Boot, as MyBatis, JdbcTemplate Jpa and multiple data sources can be configured.

In a previous article, "Spring Boot from entry to the master (D) connection (with source) MySQL database" on the basis of the article on the project's source code to achieve integration MyBatis and Spring Boot JdbcTemplate use two ways to configure multiple data sources.

Spring Boot Integration MyBatis configuration and use of the public file JdbcTemplate

1, the configuration data files application.properties source
is assumed to have two data sources configurations, respectively, and the corresponding name is oneDataSource twoDataSource.
Configuration application.properties data source information in the following documents:

spring.datasource.one.url=jdbc:mysql://123.57.47.154:3306/springboot1
spring.datasource.one.username=root
spring.datasource.one.password=wangyoodb
spring.datasource.one.driverClassName=com.mysql.cj.jdbc.Driver

spring.datasource.two.url=jdbc:mysql://123.57.47.154:3306/springboot2
spring.datasource.two.username=root
spring.datasource.two.password=wangyoodb
spring.datasource.two.driverClassName=com.mysql.cj.jdbc.Driver

2, the data source configured java class file
by the previous operation, the use of keywords and one of the two data sources to distinguish, simply increasing the information is automatically loaded Spring Boot not be necessary to increase the loading code to implement the DataSource, below small manually configure DataSourceConfig, to provide DataSource Bean.
A data source: new java class file named DataSourceOneConfig, specific code as follows:

package com.yoodb.study.demo03.datasource;

import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;

import javax.sql.DataSource;

@Configuration
@MapperScan(basePackages = "com.yoodb.study.demo03.mapper.one", sqlSessionFactoryRef = "oneSqlSessionFactory")
public class DataSourceOneConfig {
    @Bean(name = "oneDataSource")
    @Primary
    @ConfigurationProperties(prefix = "spring.datasource.one")
    public DataSource getDateSourceOne() {
        return DataSourceBuilder.create().build();
    }

    @Bean(name = "oneSqlSessionFactory")
    @Primary
    public SqlSessionFactory oneSqlSessionFactory(@Qualifier("oneDataSource") DataSource datasource)
            throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(datasource);
        bean.setMapperLocations(
                new PathMatchingResourcePatternResolver().getResources("classpath*:mapper/one/*.xml"));
        return bean.getObject();
    }
    //
    @Bean("oneSqlSessionTemplate")
    @Primary
    public SqlSessionTemplate onesqlsessiontemplate(
            @Qualifier("oneSqlSessionFactory") SqlSessionFactory sessionfactory) {
        return new SqlSessionTemplate(sessionfactory);
    }
}

Two data sources: new java class file named DataSourceTwoConfig, specific code as follows:

package com.yoodb.study.demo03.datasource;

import com.zaxxer.hikari.HikariDataSource;
import org.apache.ibatis.session.SqlSessionFactory;
import org.mybatis.spring.SqlSessionFactoryBean;
import org.mybatis.spring.SqlSessionTemplate;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.boot.autoconfigure.jdbc.DataSourceProperties;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.boot.jdbc.DataSourceBuilder;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.io.support.PathMatchingResourcePatternResolver;

import javax.sql.DataSource;

@Configuration
@MapperScan(basePackages = "com.yoodb.study.demo03.mapper.two", sqlSessionFactoryRef = "twoSqlSessionFactory")
public class DataSourceTwoConfig {
    @Bean(name = "twoDataSource")
    @ConfigurationProperties(prefix = "spring.datasource.two")
    public DataSource getDateSourceTwo(DataSourceProperties properties) {
        return DataSourceBuilder.create(properties.getClassLoader())
                .type(HikariDataSource.class)
                .driverClassName(properties.determineDriverClassName())
                .url(properties.determineUrl())
                .username(properties.determineUsername())
                .password(properties.determinePassword())
                .build();
    }
    @Bean(name = "twoSqlSessionFactory")
    public SqlSessionFactory twoSqlSessionFactory(@Qualifier("twoDataSource") DataSource datasource)
            throws Exception {
        SqlSessionFactoryBean bean = new SqlSessionFactoryBean();
        bean.setDataSource(datasource);
        bean.setMapperLocations(
                new PathMatchingResourcePatternResolver().getResources("classpath*:mapper/two/*.xml"));
        return bean.getObject();
    }
    @Bean("twoSqlSessionTemplate")
    public SqlSessionTemplate twosqlsessiontemplate(
            @Qualifier("twoSqlSessionFactory") SqlSessionFactory sessionfactory) {
        return new SqlSessionTemplate(sessionfactory);
    }
}

Notes meanings used in the above code can be written "Spring Boot analysis from entry to the master (three) common meaning and usage summary notes," the article (see micro-channel public number "Java Selection") prior reference, the following meanings using annotations :

@Configuration

Used to define the configuration class, alternative xml configuration file, the internal class annotated with one or more methods are annotated @Bean, these methods will be carried out or AnnotationConfigWebApplicationContext AnnotationConfigApplicationContext scan type, and used to construct bean definitions, initialization Spring container.

@MapperScan

To specify the scan path mapper class package, the interface configuration storage position of mybatis.

@Bean

Tell method for generating a Bean object, and then the Spring Bean object to management.

@ConfigurationProperties

Spring is type-safe property is bound Boot provided to the first Bean, for example, @ ConfigurationProperties (prefix = "spring.datasource.one") represents the use of database configuration spring.datasource.one prefix to create a DataSource.

@Primary

It will be appreciated preferentially selected as the default, not a plurality of simultaneously, this must be increased for distinguishing the primary annotation database (default database).

@Qualifier

Injecting a bean to achieve especially the role of representing the Spring container to find the object with the specified name.

note:

bean.setMapperLocations (new PathMatchingResourcePatternResolver (). getResources ( "***")) xml file location mapper form must be configured, otherwise the project will be reported no statement error message.

3, the entity class file

New entity class file, a common source of two data entity class, specific code as follows:

package com.yoodb.study.demo03.bean;

public class BootUser {
    private String id;
    private String name;
    private String detail;

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getDetail() {
        return detail;
    }

    public void setDetail(String detail) {
        this.detail = detail;
    }
}

Integrated Mybatis

1, the new mapper xml file
data source a: Create BootUserOneMapper.xml file src / main / resources / mapper / one ( add the new file does not exist), the configuration information is as follows:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.yoodb.study.demo03.mapper.one.BootUserOneMapper" >
    <resultMap id="BaseResultMap" type="com.yoodb.study.demo03.bean.BootUser" >
        <id column="id" property="id" jdbcType="VARCHAR" />
        <result column="user_name" property="name" jdbcType="VARCHAR" />
        <result column="detail" property="detail" jdbcType="VARCHAR" />
    </resultMap>

    <select id="selectAll" resultMap="BaseResultMap">
    select
         id, user_name, detail
    from boot_user order by detail asc
    </select>
</mapper>

Two data sources: Create BootUserTwoMapper.xml file src / main / resources / mapper / two (newly added file does not exist), the configuration information is as follows:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd" >
<mapper namespace="com.yoodb.study.demo03.mapper.two.BootUserTwoMapper" >
    <resultMap id="BaseResultMap" type="com.yoodb.study.demo03.bean.BootUser" >
        <id column="id" property="id" jdbcType="VARCHAR" />
        <result column="user_name" property="name" jdbcType="VARCHAR" />
        <result column="detail" property="detail" jdbcType="VARCHAR" />
    </resultMap>

    <select id="selectAll" resultMap="BaseResultMap">
    select
         id, user_name, detail
    from boot_user order by detail asc
    </select>
</mapper>

2, the new mapper interface class file

A data source: Mapper interface class file, specific code as follows:

package com.yoodb.study.demo03.mapper.one;
import com.yoodb.study.demo03.bean.BootUser;
import java.util.List;
public interface BootUserOneMapper {
　　List<BootUser> selectAll();
}

Two data sources: Mapper interface class file, specific code as follows:

package com.yoodb.study.demo03.mapper.two;
import com.yoodb.study.demo03.bean.BootUser;
import java.util.List;
public interface BootUserTwoMapper {
　　List<BootUser> selectAll();
}

3. Create a service class file
new file name BootUserService class files, the specific code as follows:

package com.yoodb.study.demo03.service;

import com.yoodb.study.demo03.bean.BootUser;
import com.yoodb.study.demo03.mapper.one.BootUserOneMapper;
import com.yoodb.study.demo03.mapper.two.BootUserTwoMapper;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

import java.util.List;

@Service
public class BootUserService {
    
    @Autowired
    private BootUserOneMapper onemapper;

    @Autowired
    private BootUserTwoMapper twomapper;

    public List<BootUser> getUsers(){
        List<BootUser> listone = onemapper.selectAll();
        List<BootUser> listtwo = twomapper.selectAll();
        listone.addAll(listtwo);
        return listone;
    }
}

4. Create a controller class file
new file name BootUserController class files, the specific code as follows:

package com.yoodb.study.demo03;

import java.util.List;

import com.yoodb.study.demo03.bean.BootUser;
import com.yoodb.study.demo03.service.BootUserService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/myt")
public class BootUserController {
    @Autowired
    private BootUserService service;

    @RequestMapping("/getUsers")
    public List<BootUser> getUsers() {
        List<BootUser> list = service.getUsers();
        return list;
    }

}

After mapper interface, xml files and physical files, service layer, controller layer is created, as shown in the directory:

5, project start

After the above operation is complete, the project start-up process console being given the wrong information is as follows:

### Error querying database. Cause: org.h2.jdbc.JdbcSQLSyntaxErrorException: Table "BOOT_USER" not found; SQL statement:
select
id, user_name, detail
from boot_user order by detail asc [42102-200]
### The error may exist in file [F:\project\study\springboot-study-demo03\target\classes\mapper\one\BootUserOneMapper.xml]
### The error may involve com.yoodb.study.demo03.mapper.one.BootUserOneMapper.selectAll
### The error occurred while executing a query
### SQL: select id, user_name, detail from boot_user order by detail asc
### Cause: org.h2.jdbc.JdbcSQLSyntaxErrorException: Table "BOOT_USER" not found; SQL statement:

问题分析：目前Spring Boot最新版本不会将application.properties文件加载到classes目录下，导致无法读取到application.properties文件信息，从而在项目访问的时候控制台报上述错误信息。
解决方法：就是在pom.xml文件中增加如下配置信息：

<resources>
    <resource>
        <!-- 指定resources插件处理哪个目录下的资源文件 -->
        <directory>src/main/resources</directory>
        <includes>
            <include>**/**</include>
        </includes>
    </resource>
</resources>

上述问题解决完后系统可以正常启动，但是在通过浏览器访问时还是会报错。

访问地址：

http://localhost:8080/myt/getUsers

错误信息如下：

### Error querying database. Cause: java.lang.IllegalArgumentException: dataSource or dataSourceClassName or jdbcUrl is required.
### The error may exist in file [F:\project\study\springboot-study-demo03\target\classes\mapper\one\BootUserOneMapper.xml]
### The error may involve com.yoodb.study.demo03.mapper.BootUserOneMapper.selectAll
### The error occurred while executing a query
### Cause: java.lang.IllegalArgumentException: dataSource or dataSourceClassName or jdbcUrl is required.] with root cause
java.lang.IllegalArgumentException: dataSource or dataSourceClassName or jdbcUrl is required.

问题分析：

1）在Spring Boot 1.* 版本中配置数据源是spring.datasource.url和spring.datasource.driverClassName；

2）在Spring Boot 2.* 版本中配置数据源是spring.datasource.jdbc-url和spring.datasource.driver-class-name；

3）Spring Boot项目中（本文是基于Spring Boot 2.3.0.M2 版本）由于无法读取到application.properties文件中“driver-class-name”和“jdbc-url”两个参数导致项目报错。

解决方法：
将application.properties文件中spring.datasource..url和spring.datasource..driverClassName分别替换成spring.datasource..jdbc-url和spring.datasource..driver-class-name。

*Spring Boot源码分析：

1）spring.datasource.*.url替换成spring.datasource.*.jdbcUrl也没有任何问题。

源码org.springframework.boot.jdbc包中DatabaseDriver.class文件反编译后，发现url参数必须以“jdbc”开始，具体源码如下：

public static DatabaseDriver fromJdbcUrl(String url) {
    if (StringUtils.hasLength(url)) {
        Assert.isTrue(url.startsWith("jdbc"), "URL must start with 'jdbc'");
        String urlWithoutPrefix = url.substring("jdbc".length()).toLowerCase(Locale.ENGLISH);
        DatabaseDriver[] var2 = values();
        int var3 = var2.length;

        for(int var4 = 0; var4 < var3; ++var4) {
            DatabaseDriver driver = var2[var4];
            Iterator var6 = driver.getUrlPrefixes().iterator();

            while(var6.hasNext()) {
                String urlPrefix = (String)var6.next();
                String prefix = ":" + urlPrefix + ":";
                if (driver != UNKNOWN && urlWithoutPrefix.startsWith(prefix)) {
                    return driver;
                }
            }
        }
    }

    return UNKNOWN;
}

2）spring.datasource.*.driverClassName不替换也没有影响。

源码org.springframework.boot.autoconfigure.jdbc包中ConfigurationProperties.class文件反编译后，发现属性即为driverClassName字段，具体源码如下：

public String determineDriverClassName() {
    if (StringUtils.hasText(this.driverClassName)) {
        Assert.state(this.driverClassIsLoadable(), () -> {
            return "Cannot load driver class: " + this.driverClassName;
        });
        return this.driverClassName;
    } else {
    ...

修改application.properties文件配置，参考信息如下：

spring.datasource.one.jdbc-url=jdbc:mysql://123.57.47.154:3306/springboot1
spring.datasource.one.username=root
spring.datasource.one.password=wangyoodb
spring.datasource.one.driver-class-name=com.mysql.cj.jdbc.Driver

spring.datasource.two.jdbc-url=jdbc:mysql://123.57.47.154:3306/springboot2
spring.datasource.two.username=root
spring.datasource.two.password=wangyoodb
spring.datasource.two.driver-class-name=com.mysql.cj.jdbc.Driver

引入话题
之前有群里的网友问Spring Boot中jdbc-url和url有什么区别？（题外话：关注微信公众号“Java精选”，留言切换工会总好后台发送消息可以进群，群内只允许探讨技术，完全免费，帮助大家解决各位技术难题。）
相信现在通过上述的分析，大家应该很清楚了吧，两者是因为Spring Boot升级版本调整了源码，所以“url”参数被重新命名了。
至此集成mybatis实现多数据源的方法已完成，项目启动成功后可以正常访问，通过浏览器访问输出如下信息：

[{"id":"1","name":"素文宅博客","detail":"欢迎关注“Java精选”微信公众号，专注程序员推送一些Java开发知识，包括基础知识、各大流行框架（Mybatis、Spring、Spring Boot等）、大数据技术（Storm、Hadoop、MapReduce、Spark等）、数据库（Mysql、Oracle、NoSQL等）、算法与数据结构、面试专题、面试技巧经验、职业规划以及优质开源项目等。"},{"id":"2","name":"素文宅博客导航","detail":"欢迎关注“Java精选”微信公众号，一部分由小编总结整理，另一部分来源于网络上优质资源，希望对大家的学习和工作有所帮助。"}]

使用JdbcTemplate
1、新增controller类文件
新增文件名JdbcTemplateController类文件，具体代码如下：

package com.yoodb.study.demo03;

import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

import com.yoodb.study.demo03.bean.BootUser;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import javax.annotation.Resource;

@RestController
@RequestMapping("/jte")
public class JdbcTemplateController {
    @Autowired
    private JdbcTemplate oneSqlSessionTemplate;

    @Autowired
    private JdbcTemplate twoSqlSessionTemplate;

    @RequestMapping("/getOneUsers")
    public List<Map<String, Object>> getOneUsers(){
        String sql = "select * from boot_user";
        List<Map<String, Object>> list =  twoSqlSessionTemplate.queryForList(sql);
        for (Map<String, Object> map : list) {
            Set<Entry<String, Object>> entries = map.entrySet( );
            if(entries != null) {
                Iterator<Entry<String, Object>> iterator = entries.iterator( );
                while(iterator.hasNext( )) {
                    Entry<String, Object> entry =(Entry<String, Object>) iterator.next( );
                    Object key = entry.getKey( );
                    Object value = entry.getValue();
                    System.out.println(key+":"+value);
                }
            }
        }
        return list;
    }

    @RequestMapping("/getTwoUsers")
    public List<BootUser> getTwoUsers() {
        List<BootUser> list = twoSqlSessionTemplate.query("select id,user_name " +
                "name,detail from boot_user", new BeanPropertyRowMapper<>(BootUser.class));
        return list;
    }
    
}

多数据源配置文件、多数据源类文件、实体类文件、controller层创建完成后，目录如图：

上述操作完成后，因为集成mybatis时部分代码已存在（配置多数据源类文件），所以使用JdbcTemplate配置完成。

2、项目启动

项目启动后访问多数据源一请求地址：
http://localhost:8080/jte/getOneUsers
通过浏览器访问输出如下信息：

[{"id":1,"user_name":"素文宅博客","password":"e10adc3949ba59abbe56e057f20f883e","role_name":"素文宅博客","detail":"欢迎关注“Java精选”微信公众号，专注程序员推送一些Java开发知识，包括基础知识、各大流行框架（Mybatis、Spring、Spring Boot等）、大数据技术（Storm、Hadoop、MapReduce、Spark等）、数据库（Mysql、Oracle、NoSQL等）、算法与数据结构、面试专题、面试技巧经验、职业规划以及优质开源项目等。"}]

项目启动后访问多数据源二请求地址：
http://localhost:8080/jte/getTwoUsers
通过浏览器访问输出如下信息：

[{"id":"1","name":"素文宅博客","detail":"欢迎关注“Java精选”微信公众号，专注程序员推送一些Java开发知识，包括基础知识、各大流行框架（Mybatis、Spring、Spring Boot等）、大数据技术（Storm、Hadoop、MapReduce、Spark等）、数据库（Mysql、Oracle、NoSQL等）、算法与数据结构、面试专题、面试技巧经验、职业规划以及优质开源项目等。"}]

Spring容器中JdbcTemplate提供了两种注入方式，一种是使用@Resource注解，直接通过byName的方式注入进来，另外一种就是@Autowired注解加上@Qualifier注解，两者联合起来，实际上也是byName。

注意：

将JdbcTemplate注入成功后，oneSqlSessionTemplate和twoSqlSessionTemplate此时就代表操作不同的数据源，使用不同的JdbcTemplate操作不同的数据源，实现了多数据源配置。
Spring Boot从入门到精通项目源码（多数据源配置springboot-study-demo03）地址：
https://github.com/yoodb/springboot
至此，Spring Boot集成MyBatis和使用JdbcTemplate两种方式多数据源配置完成，下面大家有什么问题欢迎留言评论。