接口定义：

package com.mybatis.dao;

import com.mybatis.bean.Employee;

public interface EmployeeMapper {

    public void updateEmp(Employee employee);

    public void updateEmployee(Employee employee);

}

mapper定义：

<?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.mybatis.dao.EmployeeMapper">

    <update id="updateEmp">

        update tbl_employee

        <set>

            <if test="lastName!=null">

                last_name=#{lastName},

            </if>

            <if test="email!=null">

                email=#{email},

            </if>

            <if test="gender!=null">

                gender=#{gender}

            </if>

        </set>

        where id=#{id}

    </update>

    <update id="updateEmployee">

        update tbl_employee

        <trim prefix="set" suffixOverrides=",">

            <if test="lastName!=null">

                last_name=#{lastName},

            </if>

            <if test="email!=null">

                email=#{email},

            </if>

            <if test="gender!=null">

                gender=#{gender}

            </if>

        </trim>

        where id=#{id}

    </update>

</mapper>

测试代码：

package com.mybatis.demo;

import com.mybatis.bean.Employee;

import com.mybatis.dao.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.Test;

import java.io.IOException;

import java.io.InputStream;

import java.util.List;

public class MyTest {

    public SqlSessionFactory getSqlSessionFactory() throws IOException {

        String resource = "mybatis-config.xml";

        InputStream inputStream = Resources.getResourceAsStream(resource);

        return new SqlSessionFactoryBuilder().build(inputStream);

    }

    @Test

    public void test() throws IOException {

        SqlSessionFactory sqlSessionFactory = getSqlSessionFactory();

        SqlSession openSession = sqlSessionFactory.openSession(true);

        try {

            EmployeeMapper mapper = openSession.getMapper(EmployeeMapper.class);

            mapper.updateEmp(new Employee(1, "good", null, null));

            mapper.updateEmployee(new Employee(5, "test", null, null));

        } finally {

            openSession.close();

        }

    }

}