前言
最近因工作原因,需要研究下spring的事务部分和mybatis的多数据源的源码实现,这样才能更容易的在代码层面通过扩展/重写等方式去定制自己的实现。
以前虽然用过几次mybatis,但是却一直没抽出时间认真翻看下源码,趁这次机会,花点时间研究下,顺便做个笔记。
关于看源码,我向来是觉得只有一步步去debug整个流程,查看每一步的数据流向和数据状态,才会有个更清晰的深知。如果只是看的话,有些源码中各种继承、适配、代理、装饰等,会分不清当前使用的到底是哪个类。
于是乎,所谓工欲善其事,必先利其器。先搭建个极简单的mybatis的工程环境,用来调试源码。
这个工程用了spring boot+mybatis。mybatis采用java config的形式(是真心不喜欢xml配置,所以源码研究上也会避开xml的加载)
后面博文关于分析描述就会针对这个工程的配置来说了。
另外,代码中关于spring事务的注解先注释了。
说了这么多,是希望缓解自己又写了篇这么没技术含量的博客的尴尬,哎,最近这段时间写的博客确实有些凑数了。
工程代码
数据库脚本:
CREATE DATABASE `testdb` /*!40100 DEFAULT CHARACTER SET utf8 */
-- ----------------------------
-- Table structure for user
-- ----------------------------
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`age` int(11) NOT NULL,
`username` varchar(255) DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;
工程结构
按工程结构,列一下文件代码:
User.java
public class User {
int id;
int age;
String username;
public User() {
}
public User(int id, int age, String username) {
this.id = id;
this.age = age;
this.username = username;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", age=" + age +
", username='" + username + '\'' +
'}';
}
}
MybatisConfig.java
@Configuration
@MapperScan(basePackageClasses = {UserDao.class})
//@EnableTransactionManagement //启用spring事务
public class MybatisConfig {
@Autowired
private Environment environment;
// 数据源配置
@Bean
public DataSource dataSource() {
// mybatis自带的一个简易数据库连接池,只是为了debug代码,这个就不关心了
PooledDataSource pooledDataSource = new PooledDataSource();
pooledDataSource.setDriver(environment.getProperty("mysql.driver"));
pooledDataSource.setUsername(environment.getProperty("mysql.username"));
pooledDataSource.setPassword(environment.getProperty("mysql.passwd"));
pooledDataSource.setUrl(environment.getProperty("mysql.url"));
return pooledDataSource;
}
// spring事务管理的基础bean,事务部分会用到
@Bean
public PlatformTransactionManager transactionManager(DataSource dataSource) {
DataSourceTransactionManager transactionManager = new DataSourceTransactionManager();
transactionManager.setDataSource(dataSource);
return transactionManager;
}
@Bean
public SqlSessionFactoryBean sqlSessionFactoryBean(DataSource dataSource) throws IOException {
SqlSessionFactoryBean sqlSessionFactoryBean = new SqlSessionFactoryBean();
sqlSessionFactoryBean.setDataSource(dataSource);
ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
sqlSessionFactoryBean.setMapperLocations(resourcePatternResolver.getResources("classpath:/mapper/*.xml"));
return sqlSessionFactoryBean;
}
}
UserController.java
@RestController
@RequestMapping("/user")
public class UserController {
@Autowired
IUserService userService;
@GetMapping("/save")
public String saveUser() {
User user = new User(10, 100, "test user");
try {
return userService.saveUser(user) ? "save success" : "save fail";
} catch (Exception ignore) {
ignore.printStackTrace();// 不打印日志了,堆栈信息直接打到控制台看
return "save error: " + ignore.getMessage();
}
}
@GetMapping("/list")
public String getUsers() throws Exception {
return userService.getUsers().toString();
}
@GetMapping("/delete")
public String deleteUser() throws Exception {
return userService.deleteUser() ? "delete success" : "delete fail";
}
}
UserDao.java
@Repository
public interface UserDao {
boolean saveUser(User user);
List<User> getUsers();
boolean deleteUser();
}
UserServiceImpl.java
@Service
public class UserServiceImpl implements IUserService {
@Autowired
UserDao userDao;
//@Transactional //指定这个方法的事务属性
@Override
public boolean saveUser(User user) throws Exception {
boolean success = userDao.saveUser(user);
// spring事务能力测试的时候,使用下面这段代码
/*if (true) {
throw new RuntimeException();
}*/
return success;
}
@Override
public List<User> getUsers() throws Exception {
return userDao.getUsers();
}
@Override
public boolean deleteUser() throws Exception {
return userDao.deleteUser();
}
}
IUserService.java
public interface IUserService {
boolean saveUser(User user) throws Exception;
List<User> getUsers() throws Exception;
boolean deleteUser() throws Exception;
}
WebApplication.java
@SpringBootApplication
public class WebApplication {
public static void main(String[] args) {
SpringApplication.run(WebApplication.class, args);
}
}
UserMapper.xml
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper 3.0" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.xuxd.demo.dao.UserDao">
<sql id="user_column">
id,age,username
</sql>
<select id="getUsers" resultType="com.xuxd.demo.beans.User">
select * from user
</select>
<!-- 增加用户 -->
<insert id="saveUser" parameterType="com.xuxd.demo.beans.User">
insert into user
(<include refid="user_column"/>)
values
(#{id},#{age},#{username})
</insert>
<delete id="deleteUser">
DELETE from USER where id = 10
</delete>
</mapper>
application.properties
#data source config
mysql.driver=com.mysql.jdbc.Driver
mysql.username=root
mysql.passwd=123456
mysql.url=jdbc:mysql://localhost:3306/testdb?useSSL=false
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.xuxd</groupId>
<artifactId>spring-mybatis.demo</artifactId>
<version>1.0-SNAPSHOT</version>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>1.5.6.RELEASE</version>
</parent>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-jdbc</artifactId>
<version>4.3.1.RELEASE</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.3.1</version>
</dependency>
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis-spring</artifactId>
<version>1.2.5</version>
</dependency>
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.43</version>
</dependency>
</dependencies>
</project>
后续就用这个工程debug源码了。