第一章：增删改查-Mybatis合辑2-Mybatis映射文件

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- 示例：
- 导入相关 jar 包的 Maven 坐标：

```
<dependency>
    <groupId>org.mybatis</groupId>
    <artifactId>mybatis</artifactId>
    <version>3.5.5</version>
</dependency>
<dependency>
    <groupId>log4j</groupId>
    <artifactId>log4j</artifactId>
    <version>1.2.17</version>
</dependency>
<dependency>
    <groupId>mysql</groupId>
    <artifactId>mysql-connector-java</artifactId>
    <version>8.0.21</version>
</dependency>
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.13</version>
    <scope>test</scope>
</dependency>
```

- db.properties

```
jdbc.url=jdbc:mysql://192.168.134.100:3306/test?useUnicode=true&characterEncoding=UTF-8&autoReconnect=true&useSSL=false&serverTimezone=GMT%2B8&allowPublicKeyRetrieval=true
jdbc.driverClass=com.mysql.cj.jdbc.Driver
jdbc.username=root
jdbc.password=123456
```
- log4j.xml

```
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
 
<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
 
 <appender name="STDOUT" class="org.apache.log4j.ConsoleAppender">
   <param name="Encoding" value="UTF-8" />
   <layout class="org.apache.log4j.PatternLayout">
    <param name="ConversionPattern" value="%-5p %d{MM-dd HH:mm:ss,SSS} %m  (%F:%L) \n" />
   </layout>
 </appender>
 <logger name="java.sql">
   <level value="debug" />
 </logger>
 <logger name="org.apache.ibatis">
   <level value="info" />
 </logger>
 <root>
   <level value="debug" />
   <appender-ref ref="STDOUT" />
 </root>
</log4j:configuration>
```
- Employee.java

```
package com.sunxiaping.domain;

import org.apache.ibatis.type.Alias;

@Alias("emp")
public class Employee {

private Integer id;

private String lastName;

private String email;

private String gender;

public Employee() {
    }

public Employee(Integer id, String lastName, String email, String gender) {
        this.id = id;
        this.lastName = lastName;
        this.email = email;
        this.gender = 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.sunxiaping.mapper;

import com.sunxiaping.domain.Employee;

public interface EmployeeMapper {

/**
     * 根据id查询员工的信息
     *
     * @param id
     * @return
     */
    Employee findById(Integer id);

/**
     * 增加员工信息
     *
     * @param employee
     */
    void addEmp(Employee employee);

/**
     * 修改员工信息
     *
     * @param employee
     */
    void updateEmp(Employee employee);

/**
     * 根据id删除员工信息
     *
     * @param id
     */
    void deleteEmpById(Integer id);

}
```
- EmployeeMapper.xml

```
<?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.sunxiaping.mapper.EmployeeMapper">
    <select id="findById" resultType="com.sunxiaping.domain.Employee">
        SELECT id,last_name as lastName,email,gender
        FROM employee
        WHERE id = #{id,jdbcType=INTEGER}
    </select>

<insert id="addEmp">
        INSERT INTO employee (last_name,email,gender)
        VALUES (#{lastName,jdbcType=VARCHAR},#{email,jdbcType=VARCHAR},#{gender,jdbcType=VARCHAR})
    </insert>

<update id="updateEmp">
        UPDATE employee
        SET last_name = #{lastName,jdbcType=VARCHAR},email = #{email,jdbcType=VARCHAR},gender=#{gender,jdbcType=VARCHAR}
        WHERE id = #{id,jdbcType=INTEGER}
    </update>
    <delete id="deleteEmpById">
        DELETE FROM employee
        WHERE id = #{id,jdbcType=INTEGER}
    </delete>
</mapper>
```
- mybatis-copnfig.xml

```
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>

</configuration>
```
- 测试：

```
package com.sunxiaping;

import com.sunxiaping.domain.Employee;
import com.sunxiaping.mapper.EmployeeMapper;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;

public class EmployeeTest {
    SqlSessionFactory sqlSessionFactory = null;
    SqlSession sqlSession = null;
    EmployeeMapper employeeMapper = null;

@Before
    public void before() throws IOException {
        String resource = "mybatis-config.xml";
        InputStream inputStream = Resources.getResourceAsStream(resource);
        sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        sqlSession = sqlSessionFactory.openSession(true);
        employeeMapper = sqlSession.getMapper(EmployeeMapper.class);
    }

@After
    public void after() {
        if (null != sqlSession) {
            sqlSession.close();
        }
    }

@Test
    public void testFindById() {

Employee employee = employeeMapper.findById(1);
        System.out.println("employee = " + employee);
    }

@Test
    public void testAddEmp() {
        Employee employee = new Employee();
        employee.setEmail("jerry@qq.com");
        employee.setGender("男");
        employee.setLastName("jerry");

employeeMapper.addEmp(employee);
    }

@Test
    public void testUpdateEmp(){

Employee employee = employeeMapper.findById(2);
        employee.setGender("女");

employeeMapper.updateEmp(employee);
    }

@Test
    public void testDeleteEmpById(){
        employeeMapper.deleteEmpById(2);

}

}
```