Mybatis源码解析之四大对象

一 环境准备

以一个最简单的例子来看看Mybatis的运行流程以及Mybatis四大对象起了什么作用。

Employee.java

package com.lxj.bean;

public class Employee {

	private Integer id;
	private String lastName;
	private String email;
	private String gender;

	public Integer getId() {
		return id;
	}

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

	public String getLastName() {
		return lastName;
	}

	public void setLastName(String lastName) {
		this.lastName = lastName;
	}

	public String getEmail() {
		return email;
	}

	public void setEmail(String email) {
		this.email = email;
	}

	public String getGender() {
		return gender;
	}

	public void setGender(String gender) {
		this.gender = gender;
	}

	@Override
	public String toString() {
		return "Employee [id=" + id + ", lastName=" + lastName + ", email=" + email + ", gender=" + gender + "]";
	}

}

EmployeeMapper.java

package com.lxj.mapper;

import com.lxj.bean.Employee;

public interface EmployeeMapper {
	  public Employee getEmpById(Integer id);
}

EmployeeMapper.xml

	
		select * from tba_emp where id = #{id}
	

mybatis-config.xml

 

二  测试

测试代码如下：

public class MybatisTest {

	@Test
	public void testMybatisSource() throws IOException {
		SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();
		SqlSession openSession = sqlSessionFactory.openSession();
		try {
			EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);
			Employee employee = mapper.getEmpById(1);
			System.out.println(employee);
		}finally {
			openSession.close();
		}
	
	}

	private SqlSessionFactory getSqlSessionFactory() throws IOException {
		String resource = "mybatis-config.xml";
		InputStream inputStream = Resources.getResourceAsStream(resource);
		SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
		return sqlSessionFactory;
	}

}

可以看到运行一切正常，下面就开始从获取SqlSessionFactory开始打一个断点：

直接 Step Into

 

StatementHandler 借助ParameterHandler设置参数，借助ResultSetHandler处理结果

三 源码分析

StatementHandler：处理sql语句预编译，设置参数等相关工作；

ParameterHandler：设置预编译参数用的

ResultSetHandler：       处理结果集

TypeHandler：在整个过程中，进行数据库类型和javaBean类型的映射

时序图如下:

四 总结

    Mybatis基本运行流程就到这里，自己过一遍源码比看几遍更有效率， 如果有什么问题请留言。