JavaWeb学习笔记（1）

Maven安装

https://blog.csdn.net/tirster/article/details/123418269

数据库连接池 Druid（对于我要做的项目来说用不上，不是面向多用户的）

Druid 连接池介绍 - 简书 (jianshu.com)

MyBatis

mybatis – MyBatis 3 | 入门

新建项目，设置依赖

在IntelliJ中新建个空项目，再新建maven框架的模块，取名mybatis_demo

在pom.xml中加入mybatis等依赖，日志依赖需要把logback.xml拖入main的资源目录

<dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.5.5</version>
        </dependency>

        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <version>42.1.1</version>
        </dependency>

        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.13</version>
            <scope>test</scope>
        </dependency>

        <dependency>
            <groupId>ch.qos.logback</groupId>
            <artifactId>logback-core</artifactId>
            <version>1.2.3</version>
        </dependency>
    </dependencies>

编写Mybatis核心配置文件

从 XML 中构建 SqlSessionFactory，在资源下新建mybatis-config.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="org.postgresql.Driver"/>
                <property name="url" value="jdbc:postgresql://localhost:5432/Test0"/>
                <property name="username" value="postgres"/>
                <property name="password" value="~"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="UserMapper.xml"/>
    </mappers>
</configuration>

映射SQL

在资源文件夹里新建UserMapper.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="test">
    <select id="selectAll" resultType="dataReceiver.User">
        select * from Test0;
    </select>
</mapper>

同时在main里新建类dataReceiver.User

package dataReceiver;

public class User {
    private int debt;
    private String name;

    public int getDebt() {
        return debt;
    }

    public void setDebt(int debt) {
        this.debt = debt;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "User{" +
                "debt=" + debt +
                ", name='" + name + '\'' +
                '}';
    }
}
//Alt+Insert快捷构建函数

编写测试类

main里新建MyBatisDemo类

import dataReceiver.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.apache.ibatis.session.SqlSession;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class MybatisDemo {
    public static void main(String[] args) throws IOException {
        //加载mybtis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sqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //执行sql
        List<User> users = sqlSession.selectList("test.selectAll");

        System.out.println(users);

        //释放资源
        sqlSession.close();
    }
}

报错：

严重: Connection error:
org.postgresql.util.PSQLException: 不支援 10 验证类型。请核对您已经组态 pg_hba.conf 文件包含客户端的IP位址或网路区段，以及驱动程序所支援的验证架构模式已被支援。

前往修改pg_hba.conf,重启postgreSql服务

Mapper代理开发

定义mapper

把mapper.xml置于同目录下，修改namespace

修改映射文件mapper.xml相对位置

测试类

public class MybatisDemo2 {
    public static void main(String[] args) throws IOException {
        //加载mybtis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sqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //执行sql
        //List<User> users = sqlSession.selectList("test.selectAll");
        //获取对于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();
    }
}

包扫描，一次导入所有mapper类，需把所有mapper类放在同一文件夹下

    <mappers>
        <!--<mapper resource="mapper/UserMapper.xml"/>-->
        <package name="mapper"/>
    </mappers>

<typeAliases>别名

增查删改练习

创建示例表

-- 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;

新建数据类Brand

package dataReceiver;

/**
 * 品牌
 *
 * alt + 鼠标左键：整列编辑
 *
 * 在实体类中，基本数据类型建议使用其对应的包装类型
 */

public class Brand {
    // id 主键
    private Integer id;
    // 品牌名称
    private String brandName;
    // 企业名称
    private String companyName;
    // 排序字段
    private Integer ordered;
    // 描述信息
    private String description;
    // 状态：0：禁用  1：启用
    private Integer status;


    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getBrandName() {
        return brandName;
    }

    public void setBrandName(String brandName) {
        this.brandName = brandName;
    }

    public String getCompanyName() {
        return companyName;
    }

    public void setCompanyName(String companyName) {
        this.companyName = companyName;
    }

    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 +
                ", brandName='" + brandName + '\'' +
                ", companyName='" + companyName + '\'' +
                ", ordered=" + ordered +
                ", description='" + description + '\'' +
                ", status=" + status +
                '}';
    }
}

在Test里新建测试类

package test;

import dataReceiver.Brand;
import mapper.BrandMapper;
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 MyBatisTest {
    @Test
    public void testSelectAll() throws IOException {
        //加载mybtis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sqlSession对象，用它执行sql
        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();
    }
}

BrandMapper类

package mapper;

import  dataReceiver.Brand;

import java.util.List;

public interface BrandMapper {
    public List<Brand> selectAll();
}

BrandMapper映射表

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.BrandMapper">
    <select id="selectAll" resultType="dataReceiver.Brand">
        select * from tb_brand;
    </select>
</mapper>

数据库字段与数据接收类的字段名不一致时的解决方法：

1 sql查询时起别名

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.BrandMapper">
    <!--<select id="selectAll" resultType="dataReceiver.Brand">
        select * from tb_brand;
    </select>-->

    <select id="selectAll" resultType="dataReceiver.Brand">
        select id,brand_name as BrandName,company_name as companyName,ordered,description,status from tb_brand;
    </select>
</mapper>

将sql片段存储为别名方便调用

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.BrandMapper">
    <!--<select id="selectAll" resultType="dataReceiver.Brand">
        select * from tb_brand;
    </select>-->
    <sql id="brand_column">
        id,brand_name as BrandName,company_name as companyName,ordered,description,status
    </sql>
    <select id="selectAll" resultType="dataReceiver.Brand">
        select <include refid="brand_column"/> from tb_brand;
    </select>
</mapper>

2 resultmap

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper
        PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="mapper.BrandMapper">

    //id唯一标识，type映射的类型，id（主键），result（普通字段），column数据库字段名，property别名
    <resultMap id="brandResultMap" type="dataReceiver.Brand">
        <result column="brand_name" property="brandName" />
        <result column="company_name" property="companyName" />
    </resultMap>
    <select id="selectAll" resultMap="brandResultMap">
        select * from tb_brand;
    </select>
</mapper>

查询时接收参数

//BrandMapper.xml 
   <select id="selectById" resultMap="brandResultMap">

        //#{}替换为？防止注入
        //${}拼sql，存在被注入，可用于动态表名
        select * from tb_brand where id = #{id};
    </select>
    //可以设置传入变量类型
    <select id="selectById" parameterType="int" resultMap="brandResultMap">
//BrandMapper
    //public可以不写
     Brand selectById(int id);
//MyBatisTest
@Test
    public void testSelectById() throws IOException {
        //接受参数
        int id = 1;

        //加载mybtis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sqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();

        //获取Mapper接口的代理对象
        BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);

        //执行方法
        Brand brand = brandMapper.selectById(1);
        System.out.println(brand);

        //释放资源
        sqlSession.close();
    }

特殊字符处理

xml中 <号无法直接使用

1 转义字符 &lt;

2 CDATA区

    <select id="selectById" parameterType="int" resultMap="brandResultMap">
        select * from tb_brand where id 
        <![CDATA[
            <
        ]]>
        #{id};
    </select>

条件查询

方法1 函数设置注解Param

//BrandMapper.xml
    <!--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>
//BrandMapper
     List<Brand> selectByCondition(@Param("status") int status,
                                   @Param("companyName") String companyName,
                                   @Param("brandName") String brandName);
//MyBatisTest
 @Test
    public void testSelectByCondition() throws IOException {
        //接受参数
        int status = 1;
        String companyName = "华为";
        String brandName = "华为";
        companyName = "%" + companyName + "%";
        brandName = "%" +brandName + "%";

        //加载mybtis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sqlSession对象，用它执行sql
        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.selectByCondition(status,companyName,brandName);
        System.out.println(brands);

        //释放资源
        sqlSession.close();
    }

方法2 传入对象

//BrandMapper
    List<Brand> selectByCondition(Brand brand);
//MyBatisTest
@Test
    public void testSelectByCondition() throws IOException {
        //接受参数
        int status = 1;
        String companyName = "华为";
        String brandName = "华为";
        companyName = "%" + companyName + "%";
        brandName = "%" +brandName + "%";

        //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
        brand.setCompanyName(companyName);
        brand.setBrandName(brandName);

        //加载mybtis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sqlSession对象，用它执行sql
        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.selectByCondition(brand);
        System.out.println(brands);

        //释放资源
        sqlSession.close();
    }

3 使用map集合

//BrandMapper
    List<Brand> selectByCondition(Map brand);
//MyBatisTest
    @Test
    public void testSelectByCondition() throws IOException {
        //接受参数
        int status = 1;
        String companyName = "华为";
        String brandName = "华为";
        companyName = "%" + companyName + "%";
        brandName = "%" +brandName + "%";

/*        //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
        brand.setCompanyName(companyName);
        brand.setBrandName(brandName);*/

        Map map = new HashMap();
        map.put("status",status);
        map.put("companyName",companyName);
        map.put("brandName",brandName);

        //加载mybtis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sqlSession对象，用它执行sql
        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.selectByCondition(map);
        System.out.println(brands);

        //释放资源
        sqlSession.close();
    }

动态条件查询

多条件动态查询

//BrandMapper.xml
    <!-- 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 companyName != '' ">
                and company_name like #{companyName}
            </if>
            <if test="brandName != null and brandName != '' ">
                and brand_name like #{brandName}
            </if>
     </select>
//MyBatisTest
@Test
    public void testSelectByCondition() throws IOException {
        //接受参数
        int status = 1;
        String companyName = "";
        String brandName = "";
        companyName = "%" + companyName + "%";
        brandName = "%" +brandName + "%";

/*        //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
        brand.setCompanyName(companyName);
        brand.setBrandName(brandName);*/

        Map map = new HashMap();
        map.put("status",status);
        map.put("companyName",companyName);
        map.put("brandName",brandName);

        //加载mybtis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sqlSession对象，用它执行sql
        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.selectByCondition(map);
        System.out.println(brands);

        //释放资源
        sqlSession.close();
    }

问题：当status不存在而后者条件存在时会导致sql语句多了and从而报错

解决方法：

1 在where后添加1=1的恒等式

2<where> 替代 where

    <!--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 companyName != '' ">
                 and company_name like #{companyName}
             </if>
             <if test="brandName != null and brandName != '' ">
                 and brand_name like #{brandName}
             </if>
         </where>
     </select>

单条件动态查询

//BrandMapper.xml

    <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>
//MyBatisTest.java
@Test
    public void testSelectByConditionSingle() throws IOException {
        //接受参数
        int status = 1;
        String companyName = "小米";
        String brandName = "";
        companyName = "%" + companyName + "%";
        brandName = "%" +brandName + "%";

        //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
        //brand.setCompanyName(companyName);
        //brand.setBrandName(brandName);

/*        Map map = new HashMap();
        map.put("status",status);
        map.put("companyName",companyName);
        map.put("brandName",brandName);*/

        //加载mybtis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sqlSession对象，用它执行sql
        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.selectByConditionSingle(brand);
        System.out.println(brands);

        //释放资源
        sqlSession.close();
    }

添加

一直在疑惑为什么我的IDE不能自动给sql补全，原来要按住alt+enter选择语言诸如设置为postgresql

注意是否设置自动提交事务

//brandMapper.java
    //添加
    void add(Brand brand);
//brandMapper.xml
    <insert id="add">
        insert into tb_brand (brand_name, company_name, ordered, description, status)
        values (#{brandName},#{companyName},#{ordered},#{description},#{status});
    </insert>
//MyBatisTest.java
@Test
    public void testAdd() throws IOException {
        //接受参数
        int status = 1;
        String companyName = "阿巴阿巴";
        String brandName = "阿巴";
        String description = "hahah";
        int order = 100;

        //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
        brand.setCompanyName(companyName);
        brand.setBrandName(brandName);
        brand.setOrdered(order);
        brand.setDescription(description);

        /*        Map map = new HashMap();
        map.put("status",status);
        map.put("companyName",companyName);
        map.put("brandName",brandName);*/

        //加载mybtis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sqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //自动提交事务
        //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.add(brand);

        //提交事务
        sqlSession.commit();

        //释放资源
        sqlSession.close();
    }

添加时获取主键

//brandMapper.xml
    <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>
//MyBatisTest.java
@Test
    public void testAdd() throws IOException {
        //接受参数
        int status = 1;
        String companyName = "阿巴阿巴";
        String brandName = "阿巴";
        String description = "hahah";
        int order = 100;

        //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
        brand.setCompanyName(companyName);
        brand.setBrandName(brandName);
        brand.setOrdered(order);
        brand.setDescription(description);

        /*        Map map = new HashMap();
        map.put("status",status);
        map.put("companyName",companyName);
        map.put("brandName",brandName);*/

        //加载mybtis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sqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //自动提交事务
        //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.add(brand);
        int id = brand.getId();
        System.out.println(id);

        //提交事务
        sqlSession.commit();

        //释放资源
        sqlSession.close();
    }

修改

修改全部字段

//brandMapper.java
    int update(Brand brand);
//brandMapper.xml
    <update id="update">
        update tb_brand
        set brand_name = #{brandName},
            company_name = #{companyName},
            ordered = #{ordered},
            description = #{description},
            status = #{status}
        where id = #{id};
    </update>
//MyBatisTest.java
    @Test
    public void testUpdate() throws IOException {
        //接受参数
        int status = 1;
        String companyName = "阿巴阿巴111";
        String brandName = "阿巴";
        String description = "hahah";
        int order = 200;
        int id = 7;

        //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
        brand.setCompanyName(companyName);
        brand.setBrandName(brandName);
        brand.setOrdered(order);
        brand.setDescription(description);
        brand.setId(id);

        /*        Map map = new HashMap();
        map.put("status",status);
        map.put("companyName",companyName);
        map.put("brandName",brandName);*/

        //加载mybtis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sqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //自动提交事务
        //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
        int count = brandMapper.update(brand);
        System.out.println(count);

        //提交事务
        sqlSession.commit();

        //释放资源
        sqlSession.close();
    }

动态字段修改

//brandMapper.xml
 <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>
//myBatisTest
 @Test
    public void testUpdate() throws IOException {
        //接受参数
        int status = 0;
        String companyName = "阿巴阿巴111";
        String brandName = "阿巴";
        String description = "hahah";
        int order = 200;
        int id = 7;

        //封装对象
        Brand brand = new Brand();
        brand.setStatus(status);
/*        brand.setCompanyName(companyName);
        brand.setBrandName(brandName);
        brand.setOrdered(order);
        brand.setDescription(description);*/
        brand.setId(id);

        /*        Map map = new HashMap();
        map.put("status",status);
        map.put("companyName",companyName);
        map.put("brandName",brandName);*/

        //加载mybtis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sqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //自动提交事务
        //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
        int count = brandMapper.update(brand);
        System.out.println(count);

        //提交事务
        sqlSession.commit();

        //释放资源
        sqlSession.close();
    }

删除

单个删除

//brandMapper.java
    void deleteById(int id);
//brandMapper.xml
    <delete id="deleteById">
        delete from tb_brand where id = #{id};
    </delete>
//myBatisTest
@Test
    public void testDeleteById() throws IOException {
        //接受参数

        int id = 7;

        //加载mybtis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sqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //自动提交事务
        //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);

        //提交事务
        sqlSession.commit();

        //释放资源
        sqlSession.close();
    }

多个删除

//brandMapper.java
    void deleteByIds(@Param("ids") int[] ids);
//brandMapper.xml
    <!--mybatis会将数组参数封装为一个Map集合
        默认array=数组
        可以用@Param注释改变map集合的默认key的名称
    -->
    <delete id="deleteByIds">
        delete from tb_brand where id
        in
            <foreach collection="ids" item="id" separator="," open="(" close=")">
                #{id}
            </foreach>
        ;
    </delete>
//myBatisTest
 @Test
    public void testDeleteByIds() throws IOException {
        //接受参数
        int[] ids = {11,12};

        //加载mybtis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sqlSession对象，用它执行sql
        SqlSession sqlSession = sqlSessionFactory.openSession();
        //自动提交事务
        //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);

        //提交事务
        sqlSession.commit();

        //释放资源
        sqlSession.close();
    }

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