看代码，项目见码云 test是条件判断，当传入的参数不是null时才可以
<?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.xdl.dao.XdlUserMapper"> <!--sql片段，作用是被引用--> <sql id="xdlUser">select * from user1</sql> <select id="findAll" resultType="com.xdl.entity.XdlUser"> /* 使用include标签引用*/ <include refid="xdlUser"></include> </select> <select id="findByCondit" resultType="com.xdl.entity.XdlUser"> select * from user1 where <choose> <when test="id != null"> id = #{id} </when> <when test="username != null and username!= ''"> username = #{username} </when> <otherwise> passwd = #{passwd} </otherwise> </choose> <!--<trim prefix="where" suffixOverrides="and"> <if test="id != null"> id = #{id} and </if> <if test="username != null"> username = #{username} and </if> <if test="passwd != null"> passwd = #{passwd} and </if> </trim>--> </select> <update id="update" parameterType="com.xdl.entity.XdlUser"> update user1 <trim prefix="set" suffixOverrides=","> <if test="username != null"> username = #{username} , </if> <if test="passwd != null"> passwd = #{passwd} </if> </trim> <where> <if test="id != null"> id = #{id} </if> </where> </update> <insert id="add" parameterType="com.xdl.entity.XdlUser" useGeneratedKeys="true" keyProperty="id"> insert into user1(username,passwd) values ( <choose> <when test="passwd == '333'">'man'</when> <when test="passwd == '222'">'女'</when> <otherwise>'not all'</otherwise> </choose> ) </insert> <delete id="delMore" > delete from user1 where id in (${value }) </delete> <select id="findByList" resultType="com.xdl.entity.XdlUser"> select * from user1 where /*如果传入是集合则collection里添list,数组则array*/ <foreach collection="array" item="id" open="(" close=")" separator="or"> id = #{id} </foreach> </select> <delete id="delByList"> delete from user1 where id in <foreach collection="array" item="id" open="(" close=")" separator=","> #{id} </foreach> </delete> <insert id="insertUser"> insert into user1 values <foreach collection="array" item="user" separator=","> (null,#{user.username},#{user.passwd}) </foreach> </insert> <update id="updateMore"> <foreach collection="array" item="user"> /*注意update操作时，一定要在jdbc后面加allowMultiQueries=true，即jdbc:mysql://localhost:3306/test?allowMultiQueries=true*/ update user1 set username = #{user.username},passwd = #{user.passwd} where id = #{user.id}; </foreach> </update> </mapper>