1 Jdbc

1.1 jdbc入门使用

1. 导入驱动jar包

• 新建一个目录lib，把jar包放进去

• add as library

2. 具体代码

public class JDBCdEMO {public static void main(String[] args) throws Exception{//1.注册驱动Class.forName("com.mysql.jdbc.Driver");//2.获取连接String url = "jdbc:mysql://127.0.0.1:3306/test2";String username = "root";String password = "xxxxxx";Connection conn = DriverManager.getConnection(url, username, password);//3.定义sql语句String sql = "update account set money=2000 where id = 1";//4.获取执行对象StatementStatement stmt = conn.createStatement();//5.执行sql,返回值是指影响行数int count = stmt.executeUpdate(sql);//6.处理结果System.out.println(count);//7.释放资源stmt.close();conn.close();}
}

3. 数据库对应的数据发生改变

1.2 常用API

1.2.1 DriverManager

1. DriverManager(驱动管理类)作用

• 注册驱动
• 获取数据库连接

2. 注册驱动

是个工具类，里面大都是静态方法，后续打点获取方法名就可以，注意里面的registerDriver方法

• Class.forName中Driver点进去是个静态代码块

静态代码块中有DriverManager.registerDriver就是DriverManager的方法了

mysql驱动5的jar包，可以省略不写Class.forName，一样能跑，是因为驱动jar包中有

3. 获取数据库连接
   

1.2.2 Connection

1. 作用

• 获取执行SQL对象
• 管理事务

2. 获取执行SQL对象

• 方法createStatement()
• 方法prepareStatement()

3. 管理事务

• 开启事务：setAutoCommit(boolean autoCommit)

  • true为表示自动提交
  • false表示手动提交

• 提交事务：commit()

• 回滚事务：rollback()

• 上代码

public class JDBCDemo2 {public static void main(String[] args) throws Exception{//1.注册驱动Class.forName("com.mysql.jdbc.Driver");//2.获取连接String url = "jdbc:mysql://127.0.0.1:3306/test2";String username = "root";String password = "xxxxxx";Connection conn = DriverManager.getConnection(url, username, password);//3.定义sql语句String sql1 = "update account set money=3000 where id = 1";String sql2 = "update account set money=3000 where id = 2";//4.获取执行对象StatementStatement stmt = conn.createStatement();//使用try，catch来管理事务//5.执行sql,返回值是指影响行数try {//6.开启事务conn.setAutoCommit(false);int count1 = stmt.executeUpdate(sql1);System.out.println(count1);int count2 = stmt.executeUpdate(sql2);System.out.println(count2);//7.提交事务conn.commit();} catch (Exception e) {//8.回滚事务conn.rollback();}//9.释放资源stmt.close();conn.close();}
}

1.2.3 Statement

1. 概述

• 通过conn.createStatement()创建stmt
• 在使用executeUpdate(sql)指定sql语句

        Statement stmt = conn.createStatement();//5.执行sql,返回值是指影响行数int count = stmt.executeUpdate(sql);

2. 执行SQL语句

• DML可以在最后进行判断是否成功

        if(count>0){System.out.println("修改成功");}else {System.out.println("修改失败");}

• DDL的成功不依赖返回值0或者1，因此只要不报异常即可

代码无变动

1.2.4 ResultSet

1. 作用

封装了DQL查询语句的结果

2. 代码

public class JDBCDemo4 {@Testpublic void testResultSet() throws Exception{//1.注册驱动Class.forName("com.mysql.jdbc.Driver");//2.获取连接String url = "jdbc:mysql://127.0.0.1:3306/test2";String username = "root";String password = "xxxxxx";Connection conn = DriverManager.getConnection(url, username, password);//3.定义sqlString sql = "select * from account";//4.获取statement对象Statement stmt = conn.createStatement();//5.执行sqlResultSet rs = stmt.executeQuery(sql);//6.处理结果，遍历rs中的所有数据//6.1光标向下移动一行，并且判断当前行是否有数据while (rs.next()){//6.2获取数据,可以是列索引，也可以是列名称int id = rs.getInt(1);String name = rs.getString("name");double money = rs.getDouble(3);System.out.println(id);System.out.println(name);System.out.println(money);System.out.println("---------------------");}//7.释放资源rs.close();stmt.close();conn.close();}
}

3. 再来个案例

• 需求：查询account账户表数据，封装为Account对象中，并存储到ArrayList集合中

• 新建一个实体类对象

public class Account {private int id;private String name;private double money;public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public double getMoney() {return money;}public void setMoney(double money) {this.money = money;}@Overridepublic String toString() {return "Account{" +"id=" + id +", name='" + name + '\'' +", money=" + money +'}';}
}

• 核心实现

    @Testpublic void testResultSet2() throws Exception{//1.注册驱动Class.forName("com.mysql.jdbc.Driver");//2.获取连接String url = "jdbc:mysql://127.0.0.1:3306/test2";String username = "root";String password = "xxxxxx";Connection conn = DriverManager.getConnection(url, username, password);//3.定义sqlString sql = "select * from account";//4.获取statement对象Statement stmt = conn.createStatement();//5.执行sqlResultSet rs = stmt.executeQuery(sql);ArrayList list = new ArrayList<>();//6.处理结果，遍历rs中的所有数据//6.1光标向下移动一行，并且判断当前行是否有数据while (rs.next()){Account account = new Account();//6.2获取数据int id = rs.getInt(1);String name = rs.getString("name");double money = rs.getDouble(3);//6.3赋值给对象account.setId(id);account.setName(name);account.setMoney(money);//存入集合list.add(account);}System.out.println(list);//7.释放资源rs.close();stmt.close();conn.close();}
}

1.2.5 PreparedStatement

1. SQL注入概念

• 代码

    @Testpublic void testResultSet2() throws Exception {//2.获取连接String url = "jdbc:mysql://127.0.0.1:3306/test2";String username = "root";String password = "xxxxxx";Connection conn = DriverManager.getConnection(url, username, password);// 接收用户输入 用户名和密码String name = "zhangsan";String pwd = "' or '1' = '1";String sql = "select * from tb_user where username = '" + name + "' and password = '" + pwd + "'";// 获取stmt对象Statement stmt = conn.createStatement();// 执行sqlResultSet rs = stmt.executeQuery(sql);// 判断登录是否成功if (rs.next()) {System.out.println("登录成功~");} else {2.System.out.println("登录失败~");}//7. 释放资源rs.close();stmt.close();conn.close();}
}

2. 解决

• sql不使用拼接
• sql传给prepareStatement中
• 再用setString获取变量的值
• 最终执行

	   @Testpublic void testResultSet2() throws Exception {//2.获取连接String url = "jdbc:mysql://127.0.0.1:3306/test2";String username = "root";String password = "xxxxxx";Connection conn = DriverManager.getConnection(url, username, password);// 接收用户输入 用户名和密码String name = "zhangsan";String pwd = "' or '1' = '1";//定义sqlString sql = "select * from tb_user where username = ? and password = ?";//获取pstmt对象PreparedStatement pstmt = conn.prepareStatement(sql);//设置问号值pstmt.setString(1,name);pstmt.setString(2,pwd);//指定sqlResultSet rs = pstmt.executeQuery();// 判断登录是否成功if (rs.next()) {System.out.println("登录成功~");} else {System.out.println("登录失败~");}//7. 释放资源rs.close();pstmt.close();conn.close();}
}

1.3 数据库连接池

1. 连接池简介

允许重复使用一个现有的数据库连接，而不是重新新建一个，保证了资源的复用

2. Druid连接池使用

• jar包粘贴到lib后，add as library变成模块有效

• 代码

/*** Druid数据库连接池演示*/
public class DruidDemo {public static void main(String[] args) throws Exception {//1.导入jar包//2.定义配置文件//3.加载配置文件Properties prop = new Properties();prop.load(new FileInputStream("C:\\Users\\CZyue\\Desktop\\javaSE\\11-JavaWeb补充\\jdbc-demo\\src\\druid.properties"));//4.获取连接池对象DataSource dataSource = DruidDataSourceFactory.createDataSource(prop);//5.获取对应的数据库连接ConnectionConnection connection = dataSource.getConnection();System.out.println(connection);//获取当前路径//System.out.println(System.getProperty("user.dir"));//C:\Users\CZyue\Desktop\javaSE\11-JavaWeb补充\jdbc-demo}
}

2 Mybatis

2.1 什么是Mybatis

1. 作用

• 用于简化JDBC

2. 持久层

JavaEE三层架构：表现层、业务层、持久层

3. JDBC缺点

• 硬编码
  • 体现在驱动连接信息可能发生改变
  • sql语句也可能发生改变
• 操作繁琐
  • ？问号需要手动编译
  • 对结果进行对象封装结果集的时候比较繁琐

2.2 mybatis快速入门

1. 去官网下载maven依赖https://mybatis.net.cn/getting-started.html

org.mybatismybatisx.x.x

2. 去maven仓库下载mysql驱动

mysqlmysql-connector-java5.1.46

3. 添加slf4j日志api

org.slf4jslf4j-api1.7.20ch.qos.logbacklogback-classic1.2.3ch.qos.logbacklogback-core1.2.3

4. 配置文件方resource中

5. xml的核心配置

• 将数据库连接信息放入
• 加载了sql映射文件

6. sql映射文件的具体配置

select * from tb_user;

7.定义POJP类

public class User {private Integer id;private String username;private String password;private String gender;private String addr;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 getAddr() {return addr;}public void setAddr(String addr) {this.addr = addr;}@Overridepublic String toString() {return "User{" +"id=" + id +", username='" + username + '\'' +", password='" + password + '\'' +", gender='" + gender + '\'' +", addr='" + addr + '\'' +'}';}
}

8. 核心代码

• 1.加载Mybatis的核心配置文件，获取SqlSessionFactory
• 2.获取SqlSession对象，用它来执行sql
• 3.执行sql语句

public class MybatisDemo {public static void main(String[] args) throws IOException {//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象，用它来执行sqlSqlSession sqlSession = sqlSessionFactory.openSession();//3.执行sql语句List users = sqlSession.selectList("test.selectAll");System.out.println(users);//4.释放资源sqlSession.close();}}

9. 可以将idea中配置mysql的连接后进行连接

2.3 Mapper代理开发

1. 目的

2. 建立一个mapper的包，并新建一个UserMapper的接口

与SQL映射文件同名的Mapper接口

3. 将UserMapper接口和UserMapper.xml文件要放在一起

• 在resource下新建mapper的包，用/新建

• 将UserMapper.xml拖进去

• 重新编译下

• 结果

这两在一起了

4. 设置SQL映射文件的namespace属性为Mapper接口全限定名

5. 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，并且保持参数类型和返回值类型一致

public interface UserMapper {//返回User对象并且是list的集合，根据sql语句判断啦// 方法名和是SQL映射文件中sql语句的idList selectAll();
}

6. 更改mybatis-config中sql映射文件地址

7. 更改代码

理解：

• Mapper因为存在同名的配置文件，所以可以找到映射配置文件
• 调用方法后selectAll方法后，也是配置文件中的sql语句的id，也就可以获取sql语句了，最后返回List

    public static void main(String[] args) throws IOException {//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象，用它来执行sqlSqlSession sqlSession = sqlSessionFactory.openSession();//3.原来:执行sql语句//List users = sqlSession.selectList("test.selectAll");//3.1获取UserMapper接口的代理对象//Mapper因为存在同名的配置文件，所以可以找到映射配置文件UserMapper userMapper = sqlSession.getMapper(UserMapper.class);//执行方法//调用方法后selectAll方法后，也是配置文件中的sql语句的id，也就可以获取sql语句了，最后返回ListList users = userMapper.selectAll();System.out.println(users);//4.释放资源sqlSession.close();}
}

有个细节：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

mybatis-config.xml中

2.4 Mybatis核心配置文件

1. environment

配置多个数据源

2. typeAliases别名

• 在mybatis-config.xml中配置

给pojo中的实体类起了别名

• UserMapper.xml中就可以简写成resultType=“user”

select * from tb_user;

2.5 配置文件完成增删改查操作

2.5.1 环境配置

1. 在mybatis创建表

2. 写一个实体类
3. 写一个测试用例

在test中创建包和类写

4. 安装mybatisX插件

可以将UserMapper和UserMapper.xml匹配起来，跳转方便，以及语法检测

2.5.2 查询所有结果

1. 创建一个BrandMapper类

public interface BrandMapper {/*** 查询所有*/public List selectAll();
}

2. BrandMapper.xml中写sql

通过BrandMapper类中selectAll()的alt+enter自动生成

select * from tb_brand;

3. 在src的test中创建类，在这边写测试代码

public class MyBatisTest {@Testpublic void testSelectAll() throws IOException {//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法List brands = brandMapper.selectAll();System.out.println(brands);//5.释放资源sqlSession.close();}
}

4. 有个细节

• 改别名

Brand类中的变量名字和数据中的不同

因此通过起别名的方式保持一致

select id, brand_name as brandName, company_name as compangName,ordered, description, status from tb_brand;

• 使用sql片段

id, brand_name as brandName, company_name as compangName,ordered, description, statusselectfrom tb_brand;

• resultMap

    select*from tb_brand;

2.5.3 查询查看详情

1. 需求

接收一个id对象，然后返回brand对象

2. 在BrandMapper类中写上方法

public interface BrandMapper {/*** 查看详情：根据id查询*/Brand selectById(int id);
}

3. BrandMapper.xml中写sql

通过BrandMapper类中selectById()的alt+enter自动生成

• 注意点

• xml配置内容

    /*id和接口名称的形参保持一致id，selectById(int id)*/select * from tb_brand where id = #{id};

4. 在test中写核心代码

public class MyBatisTest {@Testpublic void testSelectId() throws IOException {//0.接收参数,现在静态，以后是动态的接收int id = 1;//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法Brand brand = brandMapper.selectById(id);System.out.println(brand);//5.释放资源sqlSession.close();}
}

2.5.4 条件查询

1. 需求分析

2. 分析

3. 散装参数代码

• BrandMapper接口

    List selectByCondition(@Param("status") int status,@Param("companyName") String companyName,@Param("brandName") String brandName);/*    List selectByCondition(Brand brand);List selectByCondition(Map map);*/

• BrandMapper.xml配置

    select * from tb_brandwhere status = #{status}and company_name like #{companyName}and brand_name like #{brandName}

• 核心代码

public class MybatisDemo {public static void main(String[] args) throws IOException {//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象，用它来执行sqlSqlSession sqlSession = sqlSessionFactory.openSession();//3.执行sql语句List users = sqlSession.selectList("test.selectAll");System.out.println(users);//4.释放资源sqlSession.close();}}

4. 实体类封装方式

• BrandMapper接口Brand brand

List selectByCondition(Brand brand);

• 核心代码

public class MyBatisTest {@Testpublic void testSelectByCondition() throws IOException {//0.接收参数,现在静态，以后是动态的接收int status = 1;String companyName = "华为";String brandName = "华为";//处理参数companyName = "%" + companyName + "%";brandName = "%" + brandName + "%";//封装对象Brand brand = new Brand();brand.setStatus(status);brand.setCompanyName(companyName);brand.setBrandName(brandName);//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法//List brands = brandMapper.selectByCondition(status, companyName, brandName);List brands = brandMapper.selectByCondition(brand);System.out.println(brands);//5.释放资源sqlSession.close();}
}

5. map集合封装参数

• BrandMapper接口Map map

List selectByCondition(Map map);

• 核心代码

    @Testpublic void testSelectByCondition() throws IOException {//0.接收参数,现在静态，以后是动态的接收int status = 1;String companyName = "华为";String brandName = "华为";//处理参数companyName = "%" + companyName + "%";brandName = "%" + brandName + "%";Map map = new HashMap<>();map.put("status",status);map.put("companyName",companyName);map.put("brandName",brandName);//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法//List brands = brandMapper.selectByCondition(status, companyName, brandName);//List brands = brandMapper.selectByCondition(brand);List brands = brandMapper.selectByCondition(map);System.out.println(brands);//5.释放资源sqlSession.close();}
}

2.5.6 动态查询条件

1. 需求

如果用户只输入了两个，而非三个，进行动态查询，称为动态SQL

2. 分析

增加if判断即可

但是mybatis对于动态SQL有着很大支撑，拥有很多标签进行处理

• if
• choose(when,otherwise)
• trim(where,set)
• foreach

3. 代码

• BrandMapper接口

    List selectByCondition(Map map);

• 使用if进行标签处理BrandMapper.xml

    select * from tb_brandwherestatus = #{status} andcompany_name like #{companyName} andbrand_name like #{brandName}

• 少输入一个看看

public class MyBatisTest {@Testpublic void testSelectByCondition() throws IOException {//0.接收参数,现在静态，以后是动态的接收int status = 1;String companyName = "华为";String brandName = "华为";//处理参数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);//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法//List brands = brandMapper.selectByCondition(status, companyName, brandName);//List brands = brandMapper.selectByCondition(brand);List brands = brandMapper.selectByCondition(map);System.out.println(brands);//5.释放资源sqlSession.close();}
}

• 恒等式解决sql方法

    select * from tb_brandwhere 1=1status = #{status}and company_name like #{companyName}and brand_name like #{brandName}

• 使用where解决sql的and问题

    select * from tb_brandstatus = #{status}and company_name like #{companyName}and brand_name like #{brandName}

2.5.7 单条件动态查询

1. 需求

2. 分析

使用mybatis中的choose(when,otherwise)，类比java的swith，case，default

3. 代码

• BrandMapper接口

    List selectByConditionSingle(Brand brand);

• 使用choose进行标签处理BrandMapper.xml

    select * from tb_brandwherestatus = #{status}company_name like #{companyName}brand_name like #{brandName}    /*一个也没写，就是where 1 = 1;以防报错*/1 = 1

• 核心代码

    @Testpublic void testSelectByCondition() throws IOException {//0.接收参数,现在静态，以后是动态的接收int status = 1;String companyName = "华为";String brandName = "华为";//处理参数companyName = "%" + companyName + "%";brandName = "%" + brandName + "%";//封装对象Brand brand = new Brand();brand.setStatus(status);//brand.setCompanyName(companyName);//brand.setBrandName(brandName);//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法//List brands = brandMapper.selectByCondition(status, companyName, brandName);//List brands = brandMapper.selectByCondition(brand);List brands = brandMapper.selectByConditionSingle(brand);System.out.println(brands);//5.释放资源sqlSession.close();}
}

或者标签

    select * from tb_brandstatus = #{status}company_name like #{companyName}brand_name like #{brandName}

2.5.8 添加

1. 需求

2. 代码

• BrandMapper接口类

    void add(Brand brand);

• BrandMapper.xml的sql语句

    insert into tb_brand(brand_name, company_name, ordered, description, status)values (#{brand_name},#{companyname},#{ordered},#{description},#{status});

• 核心代码

    @Testpublic void testAdd() throws IOException {//0.接收参数,现在静态，以后是动态的接收int status = 1;String companyName = "波导手机";String brandName = "波导";String description = "手机中的战斗机";int ordered = 100;//封装对象Brand brand = new Brand();brand.setStatus(status);brand.setCompanyName(companyName);brand.setBrandName(brandName);brand.setDescription(description);brand.setOrdered(ordered);//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession();//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法brandMapper.add(brand);//5.释放资源sqlSession.close();}

• 开启事务未提交

因此需要手动提交,增加这一行

        //5.提交事务//sqlSession.commit();

        //2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession(true);

3. 主键返回

希望有时候可以返回主键的值，即id的值

可以在xml中配置useGeneratedKeys=“true” keyProperty=“id”

    insert into tb_brand(brand_name, company_name, ordered, description, status)values (#{brandName},#{companyName},#{ordered},#{description},#{status});

• 核心代码中加入获取id的值

        brandMapper.add(brand);Integer id = brand.getId();System.out.println(id);

2.5.9 修改

1. 修改全部字段

• BrandMapper接口类

    int update(Brand brand);

• BrandMapper.xml的sql语句

    update tb_brandsetbrand_name = #{brandName},company_name = #{companyName},ordered =#{ordered},description = #{description},status = #{status}where id =#{id};

• 核心代码

 @Testpublic void testAdd() throws IOException {//0.接收参数,现在静态，以后是动态的接收int status = 1;String companyName = "波导手机";String brandName = "波导";String description = "波导手机手机中的战斗机";int ordered = 200;int id = 5;//封装对象Brand brand = new Brand();brand.setStatus(status);brand.setCompanyName(companyName);brand.setBrandName(brandName);brand.setDescription(description);brand.setOrdered(ordered);brand.setId(id);//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession(true);//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法int count = brandMapper.update(brand);System.out.println(count);//5.提交事务//sqlSession.commit();//6.释放资源sqlSession.close();}
}

2. 修改动态字段

如果传进来两个值，其他的字段没值会被修改成null

• BrandMapper.xml的sql语句

    update tb_brandbrand_name = #{brandName},company_name = #{companyName},ordered =#{ordered},description = #{description},status = #{status}where id =#{id};

• 核心代码

 @Testpublic void testAdd() throws IOException {//0.接收参数,现在静态，以后是动态的接收int status = 0;String companyName = "波导手机";String brandName = "波导";String description = "波导手机手机中的战斗机";int ordered = 200;int id = 5;//封装对象Brand brand = new Brand();brand.setStatus(status);//brand.setCompanyName(companyName);//brand.setBrandName(brandName);//brand.setDescription(description);//brand.setOrdered(ordered);brand.setId(id);//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession(true);//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法//List brands = brandMapper.selectByCondition(status, companyName, brandName);//List brands = brandMapper.selectByCondition(brand);//List brands = brandMapper.selectByConditionSingle(brand);int count = brandMapper.update(brand);System.out.println(count);//5.提交事务//sqlSession.commit();//6.释放资源sqlSession.close();}
}

2.5.10 删除

1. 删除一个

• 接口

    /*** 根据id删除*/void deleteById(int id);

• BrandMapper.xml的sql语句

    delete from tb_brand where id = #{id};

• 核心代码

    @Testpublic void testDeleteById() throws IOException {//0.接收参数,现在静态，以后是动态的接收int id = 6;//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession(true);//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法brandMapper.deleteById(id);//5.提交事务//sqlSession.commit();//6.释放资源sqlSession.close();}

2. 批量删除

• 需求

批量删除这个数据

• 接口

    /*** 批量删除*/void deleteByIds(@Param("ids") int[] ids);

• BrandMapper.xml的sql语句

    delete from tb_brand where id in(#{id});

• 核心代码

    @Testpublic void testDeleteByIds() throws IOException {//0.接收参数,现在静态，以后是动态的接收int[] ids = {5,7};//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession(true);//3.获取Mapper接口的代理对象BrandMapper brandMapper = sqlSession.getMapper(BrandMapper.class);//4.执行方法brandMapper.deleteByIds(ids);//5.提交事务//sqlSession.commit();//6.释放资源sqlSession.close();}

或者

​ void deleteByIds( int[] ids);

​

" item=“id” separator=“,”>

2.6 参数传递

1. 代码

• 接口

    User select(@Param("username") String username, @Param("password") String password);

• UserMapper类

	    select * from tb_userwhere username = #{username}and   password = #{password}

• 核心代码

        //4.执行方法String username = "zhangsan";String password = "123";userMapper.select(username,password);

2.7 注解完成增删改查

1. 原来的样子

• 接口

    User selectById(int id);

• UserMapper.xml

    select * from tb_userwhere id = #{id};

2. 使用注解

• 直接接口写

    @Select("select * from tb_user where id = #{id}")User selectById(int id);

• 核心代码

    @Testpublic void testSelectById() throws IOException {//1.加载Mybatis的核心配置文件，获取SqlSessionFactoryString resource = "mybatis-config.xml";InputStream inputStream = Resources.getResourceAsStream(resource);SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);//2.获取SqlSession对象SqlSession sqlSession = sqlSessionFactory.openSession(true);//3.获取Mapper接口的代理对象UserMapper userMapper = sqlSession.getMapper(UserMapper.class);//4.执行方法User user = userMapper.selectById(1);System.out.println(user);//5.提交事务//6.释放资源sqlSession.close();}
}