一文总结之MyBatis

MyBatis

标签（空格分隔）：一文总结

目标

MyBatis动态代码生成
映射文件
与Spring集成
与SpringBoot集成

MyBatis演示

Configuration.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>

  <settings>
    <setting name="useGeneratedKeys" value="false"/>
    <setting name="useColumnLabel" value="true"/>
  </settings>

  <typeAliases>
    <typeAlias alias="UserAlias" type="org.apache.ibatis.submitted.complex_property.User"/>
  </typeAliases> -
  <environments default="development">
    <environment id="development">
      <transactionManager type="JDBC">
        <property name="" value=""/>
      </transactionManager>
      <dataSource type="UNPOOLED">
        <property name="driver" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://127.0.0.1:3306/micro_message"/>
        <property name="username" value="root"/>
        <property name="password" value="root"/>
      </dataSource>
    </environment>
  </environments>
  
  <mappers>
    <mapper resource="com/imooc/config/sqlxml/Message.xml"/>
  </mappers>

</configuration>

映射文件

<?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="org.zln.domain.Message">

    <resultMap id="messageResult" type="message">
        <id property="id" column="ID" jdbcType="INTEGER"/>
        <result property="command" column="COMMAND" jdbcType="VARCHAR"/>
        <result property="description" column="DESCRIPTION" jdbcType="VARCHAR"/>
        <result property="content" column="CONTENT" jdbcType="VARCHAR"/>
    </resultMap>

    <select id="queryMessageList" resultMap="messageResult">
        SELECT id,command,description,content FROM message
    </select>
</mapper>

初始化配置文件

package com.imooc.db;

import java.io.IOException;
import java.io.Reader;

import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;

/**
 * 访问数据库类
 */
public class DBAccess {
    public SqlSession getSqlSession() throws IOException {
        // 通过配置文件获取数据库连接信息
        Reader reader = Resources.getResourceAsReader("com/imooc/config/Configuration.xml");
        // 通过配置信息构建一个SqlSessionFactory
        SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        // 通过sqlSessionFactory打开一个数据库会话
        SqlSession sqlSession = sqlSessionFactory.openSession();
        return sqlSession;
    }
}

Dao

package org.zln.dao;

import org.springframework.stereotype.Repository;
import org.zln.domain.Message;

import java.util.List;

/**
 * Created by sherry on 000006/7/6 19:16.
 */
@Repository
public class MessageDao extends BaseDao {

    public List<Message> queryMessageList(String command,String description){
        return sqlSessionTemplate.selectList("org.zln.domain.Message.queryMessageList");
    }
}

Spring与MyBatis集成

pom

4.0.0

<groupId>org.zln.bms</groupId>
<artifactId>bms</artifactId>
<version>1.0-SNAPSHOT</version>
<packaging>war</packaging>


<properties>
    <spring.version>4.3.7.RELEASE</spring.version>
    <slf4j-api.version>1.7.25</slf4j-api.version>
    <log4j-slf4j-impl.version>2.8.1</log4j-slf4j-impl.version>
    <log4j-core.version>2.8.1</log4j-core.version>
    <commons-lang3.version>3.5</commons-lang3.version>
    <h2.version>1.4.194</h2.version>
    <mybatis.version>3.4.2</mybatis.version>
    <mybatis-spring.version>1.3.1</mybatis-spring.version>
    <jstl.version>1.2</jstl.version>
    <servlet-api.version>4.0.0-b01</servlet-api.version>
    <jackson-databind.version>2.8.7</jackson-databind.version>
    <pagehelper.version>4.2.1</pagehelper.version>
    <junit.version>4.12</junit.version>
    <quartz.version>2.2.2</quartz.version>
    <ehcache.version>2.10.3</ehcache.version>
    <poi.version>3.16</poi.version>
    <poi-contrib.version>3.1-FINAL</poi-contrib.version>
    <commons-io.version>2.2</commons-io.version>
    <mysql-connector-java.version>5.1.42</mysql-connector-java.version>
    <lombok.version>1.16.16</lombok.version>
    <druid.version>1.0.29</druid.version>
    <mock.version>1.10.19</mock.version>
    <aspect.version>1.8.10</aspect.version>
    <thymeleaf.version>3.0.5.RELEASE</thymeleaf.version>
</properties>

<dependencies>

    <dependency>
        <groupId>joda-time</groupId>
        <artifactId>joda-time</artifactId>
        <version>2.9.7</version>
    </dependency>

    <dependency>
        <groupId>org.mybatis.generator</groupId>
        <artifactId>mybatis-generator-core</artifactId>
        <version>1.3.5</version>
    </dependency>
    <dependency>
        <groupId>org.thymeleaf</groupId>
        <artifactId>thymeleaf</artifactId>
        <version>${thymeleaf.version}</version>
        <exclusions>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-api</artifactId>
            </exclusion>
        </exclusions>
    </dependency>
    <dependency>
        <groupId>org.thymeleaf</groupId>
        <artifactId>thymeleaf-spring4</artifactId>
        <version>${thymeleaf.version}</version>
        <exclusions>
            <exclusion>
                <groupId>org.slf4j</groupId>
                <artifactId>slf4j-api</artifactId>
            </exclusion>
        </exclusions>
    </dependency>

    <!--神器-->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <version>${lombok.version}</version>
    </dependency>

    <!--MySQL驱动-->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>${mysql-connector-java.version}</version>
    </dependency>

    <!--生产环境数据源-->
    <dependency>
        <groupId>com.alibaba</groupId>
        <artifactId>druid</artifactId>
        <version>${druid.version}</version>
    </dependency>


    <!--Spring-->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-webmvc</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-tx</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context-support</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-aop</artifactId>
        <version>${spring.version}</version>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjrt</artifactId>
        <version>${aspect.version}</version>
    </dependency>
    <dependency>
        <groupId>org.aspectj</groupId>
        <artifactId>aspectjweaver</artifactId>
        <version>${aspect.version}</version>
    </dependency>


    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-test</artifactId>
        <version>${spring.version}</version>
        <scope>test</scope>
    </dependency>

    <!--Excel操作-->
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi</artifactId>
        <version>${poi.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.poi</groupId>
        <artifactId>poi-ooxml</artifactId>
        <version>${poi.version}</version>
    </dependency>
    <dependency>
        <groupId>poi</groupId>
        <artifactId>poi-contrib</artifactId>
        <version>${poi-contrib.version}</version>
    </dependency>

    <dependency>
        <groupId>commons-io</groupId>
        <artifactId>commons-io</artifactId>
        <version>${commons-io.version}</version>
    </dependency>

    <!--日志-->
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-slf4j-impl</artifactId>
        <version>${log4j-slf4j-impl.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.logging.log4j</groupId>
        <artifactId>log4j-core</artifactId>
        <version>${log4j-core.version}</version>
    </dependency>

    <!--commons-->
    <dependency>
        <groupId>org.apache.commons</groupId>
        <artifactId>commons-lang3</artifactId>
        <version>${commons-lang3.version}</version>
    </dependency>

    <!--h2嵌入式数据库-->
    <!--开发环境数据源-->
    <dependency>
        <groupId>com.h2database</groupId>
        <artifactId>h2</artifactId>
        <version>${h2.version}</version>
    </dependency>

    <!--MyBatis-->
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>${mybatis.version}</version>
    </dependency>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis-spring</artifactId>
        <version>${mybatis-spring.version}</version>
    </dependency>
    <dependency>
        <groupId>com.github.pagehelper</groupId>
        <artifactId>pagehelper</artifactId>
        <version>${pagehelper.version}</version>
    </dependency>

    <!--jstl-->
    <dependency>
        <groupId>jstl</groupId>
        <artifactId>jstl</artifactId>
        <version>${jstl.version}</version>
    </dependency>
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>${servlet-api.version}</version>
        <scope>provided</scope>
    </dependency>

    <!--jackson-databind-->
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>${jackson-databind.version}</version>
    </dependency>

    <!--junit-->
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>${junit.version}</version>
        <scope>test</scope>
    </dependency>

    <!--ehcache-->
    <dependency>
        <groupId>net.sf.ehcache</groupId>
        <artifactId>ehcache</artifactId>
        <version>${ehcache.version}</version>
    </dependency>

</dependencies>


<build>
    <finalName>${project.artifactId}</finalName>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</include>
                <include>**/*.sql</include>
                <include>**/*.html</include>
            </includes>
            <filtering>false</filtering>
        </resource>
    </resources>
    <!-- 配置插件 -->
    <plugins>
        <!-- 资源文件拷贝插件 -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-resources-plugin</artifactId>
            <version>2.7</version>
            <configuration>
                <encoding>UTF-8</encoding>
            </configuration>
        </plugin>
        <!-- java编译插件 -->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.2</version>
            <configuration>
                <source>1.8</source>
                <target>1.8</target>
                <encoding>UTF-8</encoding>
            </configuration>
        </plugin>
        <plugin>
            <groupId>org.apache.tomcat.maven</groupId>
            <artifactId>tomcat7-maven-plugin</artifactId>
            <version>2.2</version>
            <configuration>
                <port>8080</port>
                <path>/bms</path>
                <!--<url>http://192.168.25.135:8080/manager/text</url>-->
                <!--<username>tomcat</username>-->
                <!--<password>tomcat</password>-->
            </configuration>
        </plugin>
    </plugins>
</build>

Spring配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xmlns:tx="http://www.springframework.org/schema/tx"
       xmlns:p="http://www.springframework.org/schema/p" xmlns:c="http://www.springframework.org/schema/c"
       xmlns:jee="http://www.springframework.org/schema/jee"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans-4.3.xsd
       http://www.springframework.org/schema/context
       http://www.springframework.org/schema/context/spring-context-4.3.xsd
       http://www.springframework.org/schema/tx
       http://www.springframework.org/schema/tx/spring-tx-4.3.xsd http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee.xsd">

    <!--MyBatis配置-->
    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"
          p:dataSource-ref="dataSource"
          p:configLocation="classpath:myBatisConf.xml"
          p:mapperLocations="classpath:org/zln/**/*Mapper.xml"/>

    <!--扫描Mapper类-->
    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer"
          p:basePackage="org.zln"/>
    <!--sqlSessionTemplate-->
    <bean id="sqlSessionTemplate" class="org.mybatis.spring.SqlSessionTemplate"
          c:sqlSessionFactory-ref="sqlSessionFactory" primary="true"/>

    <bean id="sqlSessionTemplateBatch" class="org.mybatis.spring.SqlSessionTemplate"
          c:_0-ref="sqlSessionFactory"
          c:_1="BATCH"/>



    <!--事务管理器-->
    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager"
          p:dataSource-ref="dataSource"/>


    <!--使用注解配置事务-->
    <tx:annotation-driven transaction-manager="transactionManager"/>

</beans>

MyBatis配置文件

<?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>
    <settings>
        <!--配置日志框架-->
        <setting name="logImpl" value="LOG4J2"/>
    </settings>

    <!--别名-->
    <!--<typeAliases>-->
    <!--</typeAliases>-->

    <!-- 配置分页插件 -->
    <plugins>
        <!--正式执行SQL前,先执行实现了 interceptor 接口的类-->
        <plugin interceptor="com.github.pagehelper.PageHelper">
            <!-- 设置数据库类型 Oracle,Mysql,MariaDB,SQLite,Hsqldb,PostgreSQL六种数据库-->
            <property name="dialect" value="mysql"/>
        </plugin>
    </plugins>
</configuration>

其它

Mapper接口的生成与XML都可以使用代码生成工具生成
如果有需要修改，再在此基础上进行修改

如果需要执行批量操作，建议使用JDBC，用MyBatis有点麻烦

SpringBoot与MyBatis集成

POM

<?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>org.zln.spb</groupId>
    <artifactId>spb02-web</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>spb02-web</name>
    <description>JavaWeb开发模板</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.5.4.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
        <thymeleaf.version>3.0.2.RELEASE</thymeleaf.version>
        <thymeleaf-layout-dialect.version>2.0.4</thymeleaf-layout-dialect.version>
        <lombok.version>1.16.16</lombok.version>
        <commons-lang3.version>3.5</commons-lang3.version>
        <h2.version>1.4.194</h2.version>
        <mybatis.starter.version>1.3.0</mybatis.starter.version>
        <pagehelper.version>4.2.1</pagehelper.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>com.github.pagehelper</groupId>
            <artifactId>pagehelper</artifactId>
            <version>${pagehelper.version}</version>
        </dependency>
        <dependency>
            <groupId>com.h2database</groupId>
            <artifactId>h2</artifactId>
            <version>${h2.version}</version>
        </dependency>
        <dependency>
            <groupId>org.apache.commons</groupId>
            <artifactId>commons-lang3</artifactId>
            <version>${commons-lang3.version}</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>${lombok.version}</version>
        </dependency>

        <!--starter pom-->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-thymeleaf</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-websocket</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-jdbc</artifactId>
        </dependency>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>${mybatis.starter.version}</version>
        </dependency>


        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

数据准备

schema.sql

-- 测试用表
create table User (
  id identity
  ,username varchar(100)
  ,password varchar(100)
);

test-data.sql

insert into User (username,password) values ('姓名1','pd1');
insert into User (username,password) values ('姓名2','pd2');
insert into User (username,password) values ('姓名3','pd3');
insert into User (username,password) values ('姓名4','pd4');
insert into User (username,password) values ('姓名5','pd5');
insert into User (username,password) values ('姓名6','pd6');
insert into User (username,password) values ('姓名7','pd7');
insert into User (username,password) values ('姓名8','pd8');
insert into User (username,password) values ('姓名9','pd9');
insert into User (username,password) values ('姓名10','pd10');
insert into User (username,password) values ('姓名11','pd11');

数据源配置

package org.zln.spb.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.Primary;
import org.springframework.context.annotation.Profile;
import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseBuilder;
import org.springframework.jdbc.datasource.embedded.EmbeddedDatabaseType;

import javax.sql.DataSource;

/**
 * 数据库相关配置
 * Created by nbcoolkid on 2017-06-26.
 */
@Configuration
public class DbConfig {


    /**
     * H2嵌入式数据库，用于开发
     * @return
     */
    @Bean(destroyMethod = "shutdown")
    @Primary
    @Profile("dev")
    public DataSource dataSourceH2(){
        return new EmbeddedDatabaseBuilder()
                .setType(EmbeddedDatabaseType.H2)
                .addScript("classpath:sql/schema.sql")
                .addScript("classpath:sql/test-data.sql")
                .setScriptEncoding("UTF-8")
                .build();
    }

}

Dao

UserMapper

package org.zln.spb.dao.mapper;

import org.apache.ibatis.annotations.Mapper;
import org.zln.spb.pojo.vo.User;

/**
 * Created by nbcoolkid on 2017-06-26.
 */
@Mapper
public interface UserMapper {

    User selectByPrimaryKey(int id);

}

UserMapper.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="org.zln.spb.dao.mapper.UserMapper">
    <select id="selectByPrimaryKey" parameterType="int" resultType="org.zln.spb.pojo.vo.User">
        SELECT id,username,password FROM User where id = #{_parameter}
    </select>
</mapper>

测试

package org.zln.spb.dao.mapper;

import lombok.extern.slf4j.Slf4j;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;

import static org.junit.Assert.*;

/**
 * Created by nbcoolkid on 2017-06-26.
 */
@RunWith(SpringRunner.class)
@SpringBootTest
@Slf4j
public class UserMapperTest {

    @Autowired
    private UserMapper userMapper;

    @Test
    public void selectByPrimaryKey() throws Exception {
        System.out.println("UserMapper:"+userMapper);
        System.out.println(userMapper.selectByPrimaryKey(1));
    }

}

MyBatis配置文件详解

Mybatis映射文件详解

动态SQL元素

动态SQL

if

<if test="roleName!=null and rowName!=''">
    and role_name like concat('%',#{roleName},'%')
</if>

choose、when、otherwise

<choose>
    <when test="roleNo!=null">
        and role_no=#{roleNo}
    </when>
    <when test="roleName!=null">
        and role_name like concat('%',#{roleName},'%')
    </when>
    <otherwise>
        and note is not null
    </otherwise>
</choose>

where、trim、set

where

<where>
    <if test="roleName!=null and rowName!=''">
        and role_name like concat('%',#{roleName},'%')
    </if>
</where>

当条件满足的时候，才会拼接where关键字
而且前缀and会自动去掉

trim

<trim prefix="where" prefixOverrides="and">
    <if test="roleName!=null and rowName!=''">
        and role_name like concat('%',#{roleName},'%')
    </if>
</trim>

prefix表示语句的前缀
prefixOverrides表示需要去掉的第一个字符串，如果有多种，可以这样子prefixOverrides="and|or"

set

用于执行更新语句

update t_tole
<set>
    <if test="roleName!=null">
        tole_name=#{roleName},
    </if>
    where role_no=#{roleNo}
</set>

使用trim改写

update t_tole
<trim prefix="set" suffixOverrides=",">
    <if test="roleName!=null">
        tole_name=#{roleName},
    </if>
    where role_no=#{roleNo}
</set>

suffixOverrides表示需要去掉的最后一个字符串

foreach

    <select id="getStudentListByClassIDs" resultMap="studentResultMap">
        SELECT * FROM STUDENT_TBL ST
        WHERE ST.CLASS_ID IN
        <foreach collection="list" item="classList"  open="(" separator="," close=")">
            #{classList}
        </foreach>
    </select>

bind与模糊查询

bind一般用于模糊查询的字符串连接
MySQL中使用concat
Oracle中使用||

<select id="" resultType="">
    <bind name="pattern" value="'%'+_parameter+'%'"/>
    select * from tt where role_name like #{pattern}
</select>

如果传递过来的参数有多个，
则编写多个bind标签即可

MyBatis中使用OGNL表达式

在MyBatis中，通过使用OGNL表达式，从传递的参数中获取数据，组装SQL

String与基本数据类型　　　　_parameter

自定义类型（对象）　　　　　属性名

集合

　　数组　　　　　　　　　　array

　　List　　　　　　　　　　list

　　Map　　　　　　　　　　_parameter

获取集合中的一条数据

　　数组　　　　　　　　　　array[索引]　　　　　　基本数据类型数组

　　　　　　　　　　　　　　array[索引].属性名　　对象数据类型数组　　　　　　　　　　　　

　　List　　　　　　　　　　list[索引]

　　　　　　　　　　　　　　list[索引].属性名

　　Map　　　　　　　　　　_parameter.key

　　　　　　　　　　　　　　_parameter.key.属性名

利用foreach标签从集合中取出数据（遍历拼接SQL）

　　如果collection中的数组或List，i表示下标，如果collection是Map，i表示key。item（或item.属性名）表示迭代出来的值

　　separator 表示迭代出来的元素之间的分隔符

　　举例

<delete id="deleteBatch" parameterType="java.util.List">
      delete from MESSAGE where ID in(
          <foreach collection="list" item="item" separator=",">
              #{item}
          </foreach>
      )
  </delete>

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原文地址：https://www.cnblogs.com/sherrykid/p/7354780.html