目录
阅读提示:
本文默认已经预装预装maven
持久层框架,用于简化JDBC开发,是对JDBC的封装
持久层:
- 负责将数据保存到数据库的代码部分
- Java EE三层架构:表现层、业务层、持久层
硬编码,不利于维护
操作繁琐
硬编码 --> 配置文件
繁琐惭怍 --> 框架封装自动完成
需求:查询user表中的所有数据
SQL
create database mybatis;
use mybatis;
drop table if exists tb_user;
create table tb_user(
id int primary key auto_increment,
username varchar(20),
password varchar(20),
gender char(1),
addr varchar(30)
);
INSERT INTO tb_user VALUES (1, 'zhangsan', '123', '男', '北京');
INSERT INTO tb_user VALUES (2, '李四', '234', '女', '天津');
INSERT INTO tb_user VALUES (3, '王五', '11', '男', '西安');
代码实现
创建模块,导入坐标
在pom.xml中配置文件中添加依赖的坐标
注意:需要在项目的resources目录下创建logback的配置文件
<dependencies>
<!--mybatis 依赖-->
<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.5</version>
</dependency>
<!--mysql 驱动-->
<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.46</version>
</dependency>
<!--junit 单元测试-->
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.13</version>
<scope>test</scope>
</dependency>
<!-- 添加slf4j日志api -->
<dependency>
<groupId>org.slf4j</groupId>
<artifactId>slf4j-api</artifactId>
<version>1.7.20</version>
</dependency>
<!-- 添加logback-classic依赖 -->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-classic</artifactId>
<version>1.2.3</version>
</dependency>
<!-- 添加logback-core依赖 -->
<dependency>
<groupId>ch.qos.logback</groupId>
<artifactId>logback-core</artifactId>
<version>1.2.3</version>
</dependency>
</dependencies>
编写MyBatis核心文件
核心文件用于替换信息,解决硬编码问题
在模块下的resources目录下创建mybatis的配置文件
mybatis-config.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>
<environments default="development">
<environment id="development">
<!-- 采用JDBC的事务管理方式 -->
<transactionManager type="JDBC"/>
<!-- 数据库连接信息 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql:///mybatis?useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<!-- 加载SQL映射文件 -->
<mappers>
<mapper resource="UserMapper.xml"/>
</mappers>
</configuration>
编写SQL映射文件
SQL映射文件用于统一管理SQL语句,解决硬编码问题
在模块的resources目录下创建映射配置文件
UserMaooer.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">
<!--
namespace:命名空间
-->
<mapper namespace="test">
<!-- statement -->
<select id="selectAll" resultType="priv.dandelion.entity.User">
select * from tb_user;
</select>
</mapper>
编码
实体类
package priv.dandelion.entity;
public class User {private Integer id;
private String username;
private String password;
private String gender;
private String address;
public User() {
}
public User(Integer id, String username, String password, String gender, String address) {
this.id = id;
this.username = username;
this.password = password;
this.gender = gender;
this.address = address;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUsername() {
return username;
}
public void setUsername(String username) {
this.username = username;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public String getGender() {
return gender;
}
public void setGender(String gender) {
this.gender = gender;
}
public String getAddress() {
return address;
}
public void setAddress(String address) {
this.address = address;
}
@Override
public String toString() {
return "User{" +
"id=" + id +
", username='" + username + '\'' +
", password='" + password + '\'' +
", gender='" + gender + '\'' +
", address='" + address + '\'' +
'}';
}
}
测试类
public static void main(String[] args) throws IOException {
// 加载mybatis的核心配置文件,获取SqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 获取Session对象,执行SQL语句
SqlSession sqlSession = sqlSessionFactory.openSession();
// 执行SQL,处理结果
List<User> users = sqlSession.selectList("test.selectAll");
System.out.println(users);
// 释放资源
sqlSession.close();
}
解决形如上述测试类中
List<User> users = sqlSession.selectList("test.selectAll");
的硬编码问题
定义与SQL映射文件同名的Mapper接口,并且将Mapper接口和SQL映射文件放置在同一目录下
maven项目开发时要求code和resources分开,可在resources中创建相同包文件来是实现上述效果
设置SQL映射文件的namespace
属性未Mapper接口的全限定名
在Mapper接口中定义方法,方法名就是SQL映射文件中SQL语句的id
,并且参数类型和返回值类型一致
修改SQL映射文件UserMapper.xml
同时还要修改其路径
<?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">
<!--
namespace:命名空间
-->
<mapper namespace="priv.dandelion.mapper.UserMapper">
<select id="selectAll" resultType="priv.dandelion.entity.User">
select * from tb_user;
</select>
</mapper>
创建对应的Mapper接口UserMapper.interface
public interface UserMapper {
List<User> selectAll();
}
修改mybatis核心配置文件中加载SQL映射的<mapper></mapper>
的路径
<mappers>
<mapper resource="priv/dandelion/mapper/UserMapper.xml"/>
</mappers>
测试代码
public static void main(String[] args) throws IOException {
// 加载mybatis的核心配置文件,获取SqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
// 获取Session对象,执行SQL语句
SqlSession sqlSession = sqlSessionFactory.openSession();
// 执行SQL,处理结果
// 获取UserMapper接口的代理对象
UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
List<User> users = userMapper.selectAll();
System.out.println(users);
// 释放资源
sqlSession.close();
}
改进
如果Mapper接口名称和SQL映射文件名称相同,并在同一目录下,则可以使用包扫描的方式简化SQL映射文件的加载,简化mybatis核心配置文件
<mappers>
<!--加载sql映射文件-->
<!-- <mapper resource="priv/dandelion/mapper/UserMapper.xml"/>-->
<!--Mapper代理方式-->
<package name="priv.dandelion.mapper"/>
</mappers>
在核心配置文件的
environments
标签中其实是可以配置多个environment
,使用id
给每段环境起名,在environments
中使用default='环境id'
来指定使用哪儿段配置。我们一般就配置一个environment
即可
<?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>
<typeAliases>
<package name="priv.dandelion.entity"/>
</typeAliases>
<environments default="development">
<environment id="development">
<!-- 采用JDBC的事务管理方式 -->
<transactionManager type="JDBC"/>
<!-- 数据库连接信息 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<!-- JDBC连接数据库,SSL,Unicode字符集,UTF-8编码 -->
<property name="url" value="jdbc:mysql:///mybatis?useSSL=false&useUnicode=true&characterEncoding=UTF-8"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
<environment id="test">
<transactionManager type="JDBC"/>
<!-- 数据库连接信息 -->
<dataSource type="POOLED">
<property name="driver" value="com.mysql.jdbc.Driver"/>
<property name="url" value="jdbc:mysql:///mybatis?useSSL=false"/>
<property name="username" value="root"/>
<property name="password" value="123456"/>
</dataSource>
</environment>
</environments>
<!-- 加载SQL映射文件 -->
<mappers>
<!-- <mapper resource="priv/dandelion/mapper/UserMapper.xml"/>-->
<package name="priv.dandelion.mapper"/>
</mappers>
</configuration>
映射配置文件中的
resultType
属性需要配置数据封装的类型(类的全限定名),繁琐Mybatis 提供了
类型别名
(typeAliases) 可以简化这部分的书写
<configuration>
<!-- name属性未实体类所在的包 -->
<typeAliases>
<package name="priv.dandelion.entity"/>
</typeAliases>
</configuration>
<mapper namespace="priv.dandelion.mapper.UserMapper">
<!-- resultType的值不区分大小写 -->
<select id="selectAll" resultType="user">
select * from tb_user;
</select>
</mapper>
SQL
-- 删除tb_brand表
drop table if exists tb_brand;
-- 创建tb_brand表
create table tb_brand
(
-- id 主键
id int primary key auto_increment,
-- 品牌名称
brand_name varchar(20),
-- 企业名称
company_name varchar(20),
-- 排序字段
ordered int,
-- 描述信息
description varchar(100),
-- 状态:0:禁用 1:启用
status int
);
-- 添加数据
insert into tb_brand (brand_name, company_name, ordered, description, status)
values ('三只松鼠', '三只松鼠股份有限公司', 5, '好吃不上火', 0),
('华为', '华为技术有限公司', 100, '华为致力于把数字世界带入每个人、每个家庭、每个组织,构建万物互联的智能世界', 1),
('小米', '小米科技有限公司', 50, 'are you ok', 1);
SELECT * FROM tb_brand;
实体类
public class Brand {private Integer id;
private String brand_name;
private String company_name;
private Integer ordered;
private String description;
private Integer status;
public Brand() {
}
public Brand(
Integer id,
String brand_name,
String company_name,
Integer ordered,
String description,
Integer status
) {
this.id = id;
this.brand_name = brand_name;
this.company_name = company_name;
this.ordered = ordered;
this.description = description;
this.status = status;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getBrand_name() {
return brand_name;
}
public void setBrand_name(String brand_name) {
this.brand_name = brand_name;
}
public String getCompany_name() {
return company_name;
}
public void setCompany_name(String company_name) {
this.company_name = company_name;
}
public Integer getOrdered() {
return ordered;
}
public void setOrdered(Integer ordered) {
this.ordered = ordered;
}
public String getDescription() {
return description;
}
public void setDescription(String description) {
this.description = description;
}
public Integer getStatus() {
return status;
}
public void setStatus(Integer status) {
this.status = status;
}
@Override
public String toString() {
return "Brand{" +
"id=" + id +
", brand_name='" + brand_name + '\'' +
", company_name='" + company_name + '\'' +
", ordered=" + ordered +
", description='" + description + '\'' +
", status=" + status +
'}';
}
}
安装插件MyBatisX
步骤
本节要点:
编写接口方法
public interface BrandMapper {
public List<Brand> selectAll();
}
编写SQL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">
<!--
namespace:命名空间
-->
<mapper namespace="priv.dandelion.mapper.BrandMapper">
<!-- 起别名解决数据库和实体类字段名不同问题
<sql id="brand_column">
id, brand_name as brandName, company_name as companyName, ordered, description, status
</sql><select id="selectAll" resultType="priv.dandelion.entity.Brand">
select * from tb_brand;
select
<include refid="brand_column"/>
from tb_brand;
</select>
--><!-- resultMap解决数据库和实体类字段不同问题 -->
<resultMap id="brandResultMap" type="brand">
<result column="brand_name" property="brandName" />
<result column="company_name" property="companyName" />
</resultMap>
<!-- 不使用resultType, 使用resultMap -->
<select id="selectAll" resultMap="brandResultMap">
select *
from tb_brand;
</select>
</mapper>
编写测试方法
@Test
public void testSelectAll() throws IOException {
// 获取SqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);// 获取sqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession();
// 获取mapper接口的代理对象
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
// 执行方法
List<Brand> brands = brandMapper.selectAll();
System.out.println(brands);
// 释放资源
sqlSession.close();
}
本节要点:
使用占位符进行参数传递
占位符名称和参数保持一致
占位符
#{占位符名}
:会替换为?
,防止SQL注入,一般用于替换字段值${占位符名}
:存在SQL注入问题,一般用于执行动态SQL语句,如表名列名不固定的情况(见)编写接口方法
void update(Brand brand);
SQL映射文件查询代码标签
<resultMap id="brandResultMap" type="brand">
<result column="brand_name" property="brandName" />
<result column="company_name" property="companyName" />
</resultMap>
<select id="selectById" resultMap="brandResultMap">
select *
from tb_brand where id = #{id};
</select>
测试方法
@Test
public void testSelectByCondition() throws IOException {
// 接收参数
int status = 1;
String companyName = "华为";
String brandName = "华为"; // 获取SqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
// 获取sqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession();
// 获取mapper接口的代理对象
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
// 执行方法
companyName = "%" + companyName + "%";
brandName = "%" + brandName + "%";
List<Brand> brands = brandMapper.selectByCondition(status, companyName, brandName);
System.out.println(brands);
// 释放资源
sqlSession.close();
}</code></pre></li>
本节要点:
多条件查询
SQL映射文件
<!-- resultMap解决数据库和实体类字段不同问题 -->
<resultMap id="brandResultMap" type="brand">
<result column="brand_name" property="brandName"/>
<result column="company_name" property="companyName"/>
</resultMap>
<!-- 条件查询 -->
<select id="selectByCondition" resultMap="brandResultMap">
select *
from tb_brand
where status = #{status}
and company_name like #{companyName}
and brand_name like #{brandName}
</select>
散装参数
接口
// 散装参数
List<Brand> selectByCondition(
@Param("status")int status,
@Param("companyName")String companyName,
@Param("brandName")String brandName
);
测试方法
@Test
public void testSelectByCondition() throws IOException {
// 接收参数
int status = 1;
String companyName = "华为";
String brandName = "华为";
// 获取SqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);// 获取sqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession();
// 获取mapper接口的代理对象
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
// 执行方法
companyName = "%" + companyName + "%";
brandName = "%" + brandName + "%";
List&lt;Brand&gt; brands = brandMapper.selectByCondition(
status, companyName, brandName);
System.out.println(brands);
// 释放资源
sqlSession.close();
}</code></pre></li></ul>
对象参数
接口
// 对象参数
List<Brand> selectByCondition(Brand brand);
测试方法
// 细节不表,仅展示执行方法
// 执行方法
Brand brand = new Brand();
brand.setStatus(status);
brand.setCompanyName("%" + companyName + "%");
brand.setBrandName("%" + brandName + "%");
List<Brand> brands = brandMapper.selectByCondition(brand);
System.out.println(brands);
map集合参数
接口
// 集合参数
List<Brand> selectByCondition(Map map);
测试方法
// 细节不表,仅展示执行方法
// 执行方法
Map map = new HashMap();
map.put("status", status);
map.put("companyName", "%" + companyName + "%");
map.put("brandName", "%" + brandName + "%");
List<Brand> brands = brandMapper.selectByCondition(map);
System.out.println(brands);
多条件动态条件查询
优化条件查询,如页面上表单存在多个条件选项,但实际填写表单仅使用部分条件筛选的情况
SQL映射文件
<!-- resultMap解决数据库和实体类字段不同问题 -->
<resultMap id="brandResultMap" type="brand">
<result column="brand_name" property="brandName"/>
<result column="company_name" property="companyName"/>
</resultMap>
<!-- 动态条件查询 -->
<select id="selectByCondition" resultMap="brandResultMap">
select *
from tb_brand
<where>
<if test="status != null">
status = #{status}
</if>
<if test="companyName != null">
and company_name like #{companyName}
</if>
<if test="brandName != null">
and brand_name like #{brandName}
</if>
</where>
</select>
注:
单条件的动态条件查询
优化条件查询:如表单中存在多个条件筛选,但仅有其中一个生效的情况
使用标签
choose
标签类似于Java
中的switch
when
标签类似于Java
中的case
otherwise
标签类似于Java
中的default
SQL映射文件
<!-- resultMap解决数据库和实体类字段不同问题 -->
<resultMap id="brandResultMap" type="brand">
<result column="brand_name" property="brandName"/>
<result column="company_name" property="companyName"/>
</resultMap>
<!-- 单条件动态查询 -->
<select id="selectByConditionSingle" resultMap="brandResultMap">
select *
from tb_brand
<where>
<choose>
<when test="status != null">
status = #{status}
</when>
<when test="companyName != null and companyName != ''">
company_name like #{companyName}
</when>
<when test="brandName != null and brandName != ''">
brand_name like #{brandName}
</when>
</choose>
</where>
</select>
添加
接口
// 添加
void add(Brand brand);
SQL映射文件
<insert id="add">
insert into tb_brand (brand_name, company_name, ordered, description, status)
values (#{brandName}, #{companyName}, #{ordered}, #{description}, #{status});
</insert>
测试方法
@Test
public void testAdd() throws IOException {
// 接收参数
int status = 1;
String companyName = "aaa";
String brandName = "xxx";
String description = "这是一段介绍";
int ordered = 100;// 获取SqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
// 获取sqlSession对象
// SqlSession sqlSession = sqlSessionFactory.openSession();
SqlSession sqlSession = sqlSessionFactory.openSession(true);
// 获取mapper接口的代理对象
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
// 执行方法
Brand brand = new Brand();
brand.setStatus(1);
brand.setBrandName(brandName);
brand.setCompanyName(companyName);
brand.setDescription(description);
brand.setOrdered(ordered);
brandMapper.add(brand);
System.out.println("添加成功");
// 提交事务
// sqlSession.commit();
// 释放资源
sqlSession.close();
}
Mybatis事务
MyBatis默认手动事务,执行添加等操作时会自动回滚
MyBayis事务处理的方法
// 方法一:在获取sqlSession对象时设置参数,开启自动事务
SqlSession sqlSession = sqlSessionFactory.openSession(true);
sqlSession.close();
// 方法二:手动提交事务
SqlSession sqlSession = sqlSessionFactory.openSession();
sqlSession.commit();
sqlSession.close();
添加 - 主键返回
传入实体类对象进行数据添加,在数据添加完成后,会将
id
信息写回该实体类对象
SQL映射文件
<insert id="add" useGeneratedKeys="true" keyProperty="id">
insert into tb_brand (brand_name, company_name, ordered, description, status)
values (#{brandName}, #{companyName}, #{ordered}, #{description}, #{status});
</insert>
获取写回信息
Integer id = brand.getId();
修改整条数据
接口
// 修改,可使用int返回值,返回受影响行数
void update(Brand brand);
SQL映射文件
<update id="update">
update tb_brand
set brand_name = #{brandName},
set company_name = #{companyName},
set ordered = #{ordered},
set description = #{description},
set status = #{status}
where id = #{id};
</update>
修改部分字段
优化上述代码应对仅修改部分属性导致其他属性数据丢失问题
使用
<set></set>
标签替换set关键字列表,区别于<where></where>
标签,注意语法
SQL映射文件
<update id="update">
update tb_brand
<set>
<if test="brandName != null and brandName != ''">
brand_name = #{brandName},
</if>
<if test="companyName != null and companyName != ''">
company_name = #{companyName},
</if>
<if test="ordered != null">
ordered = #{ordered},
</if>
<if test="description != null and description != ''">
description = #{description},
</if>
<if test="status != null">
status = #{status},
</if>
</set>
where id = #{id};
</update>
测试代码
@Test
public void testUpdate() throws IOException {
// 接收参数
int id = 5;
int status = 0;
String companyName = "AAA";
String brandName = "XXX";
int ordered = 300;// 获取SqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
// 获取sqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession(true);
// 获取mapper接口的代理对象
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
// 执行方法
Brand brand = new Brand();
brand.setId(id);
brand.setStatus(status);
brand.setBrandName(brandName);
brand.setCompanyName(companyName);
brand.setOrdered(ordered);
brandMapper.update(brand);
System.out.println("修改成功");
// 释放资源
sqlSession.close();
}
删除一条数据
接口
// 删除一条数据
void deleteById(int id);
SQL映射文件
<delete id="deleteById">
delete
from tb_brand
where id = #{id};
</delete>
测试
@Test
public void testDeleteById() throws IOException {
// 接收参数
int id = 5;// 获取SqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
// 获取sqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession(true);
// 获取mapper接口的代理对象
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
// 执行方法
brandMapper.deleteById(id);
System.out.println("删除成功");
// 释放资源
sqlSession.close();
}
批量删除数据
用于解决删除时传入参数为数组的情况
使用
<foreach></foreach>
标签代替SQL语句中的id in (?, ?, ..., ?)
collection
属性为MyBatis封装后数组对应的key
,封装后属性值应为array
(见注释)
MyBatis
默认会将数组参数封装为Map
集合,其key
为array
,即array = ids
- 可在接口中对参数数组使用
@Param
注解,将封装后的key
手动命名,则可在映射文件中使用
separator
属性为分隔符
open
和close
属性分别为在<foreach></foreach>
前后拼接字符,主要用于代码规范,示例中未展示
接口
// 删除多个数据
void deleteByIds(@Param("ids")int[] ids);
SQL映射文件
<delete id="deleteByIds">
delete
from tb_brand
where id
in (
<!-- <foreach collection="array" item="id"> -->
<foreach collection="ids" item="id" separator=",">
#{id}
</foreach>
);
</delete>
测试
@Test
public void testDeleteByIds() throws IOException {
// 接收参数
int[] ids = {6, 7};// 获取SqlSessionFactory
String resource = "mybatis-config.xml";
InputStream inputStream = Resources.getResourceAsStream(resource);
SqlSessionFactory sqlSessionFactory =
new SqlSessionFactoryBuilder().build(inputStream);
// 获取sqlSession对象
SqlSession sqlSession = sqlSessionFactory.openSession(true);
// 获取mapper接口的代理对象
BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);
// 执行方法
brandMapper.deleteByIds(ids);
System.out.println("删除成功");
// 释放资源
sqlSession.close();
}
概述
多个参数
设有如下代码:
User select(@Param("username") String username,@Param("password") String password);
MyBatis会将散装的多个参数封装为Map集合
若不使用@Param
注解,则会使用以下命名规则:
map.put("arg0",参数值1);
map.put("arg1",参数值2);
map.put("param1",参数值1);
map.put("param2",参数值2);
即Map集合中的参数的key分别为arg0, arg1, param1, param2
使用@Param
注解会将Map集合中的参数的arg替换为指定内容,增强其可读性
单个参数
POJO类型:直接使用,要求属性名和参数占位符名称一致(见 5.2 SQL映射文件)
Map集合类型:直接使用,要求key和参数占位符名称一致(见 5.2 SQL映射文件)
Collection集合类型:封装Map集合,可以使用@Param注解替换Map集合中默认arg键名
map.put("arg0",collection集合);
map.put("collection",collection集合;
List集合类型:封装为Map集合,可以使用@Param注解,替换Map集合中默认的arg键名
map.put("arg0",list集合);
map.put("collection",list集合);
map.put("list",list集合);
Array类型:封装为Map集合,可以使用@Param注解,替换Map集合中默认的arg键名
map.put("arg0",数组);
map.put("array",数组);
其他类型:直接使用,与参数占位符无关,但尽量见名知意
概述
xml
中的statement
xml
配置文件,否则代码会十分混乱使用方法
注解(部分)
@Select
@Insert
@Update
@Delete
示例
使用注解简化查询
原接口
Brand selectById(int id);
原SQL映射文件
<!-- resultMap解决数据库和实体类字段不同问题 --> <resultMap id="brandResultMap" type="brand"> <result column="brand_name" property="brandName"/> <result column="company_name" property="companyName"/> </resultMap> <select id="selectById" resultMap="brandResultMap"> select * from tb_brand where id = #{id}; </select>
使用注解进行开发
接口
@ResultMap("brandResultMap") // 解决数据库和实体类字段名称不同
@Select("select * from tb_brand where id = #{id}") // 查询语句
Brand selectById(int id);
SQL映射文件:不再需要原先的statement
<!-- resultMap解决数据库和实体类字段不同问题 -->
<resultMap id="brandResultMap" type="brand">
<result column="brand_name" property="brandName"/>
<result column="company_name" property="companyName"/>
</resultMap>
<!--
<select id="selectById" resultMap="brandResultMap">
select *
from tb_brand
where id = #{id};
</select>
-->
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