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  • Mybatis多表查询

    1.Mybatis多表查询

    1.1 一对一查询

    1.1.1 一对一查询的模型MapperScannerConfigurer

    用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

    一对一查询的需求：查询一个订单，与此同时查询出该订单所属的用户

    图片1

    1.1.2一对一查询的语句

    对应的sql语句：select * from orders o,user u where o.uid=u.id;

    查询的结果如下：

    图片2

    1.1.3 创建Order和User实体
    public class Order {

    private int id;
    private Date ordertime;
    private double total;

    //代表当前订单从属于哪一个客户
    private User user;
}

public class User {
    
    private int id;
    private String username;
    private String password;
    private Date birthday;

}
    1.1.4 创建OrderMapper接口
    public interface OrderMapper {
    List<Order> findAll();
}
    1.1.5 配置OrderMapper.xml
    <mapper namespace="com.itheima.mapper.OrderMapper">
    <resultMap id="orderMap" type="com.itheima.domain.Order">
        <result column="uid" property="user.id"></result>
        <result column="username" property="user.username"></result>
        <result column="password" property="user.password"></result>
        <result column="birthday" property="user.birthday"></result>
    </resultMap>
    <select id="findAll" resultMap="orderMap">
        select * from orders o,user u where o.uid=u.id
    </select>
</mapper>

    其中还可以配置如下：

    <resultMap id="orderMap" type="com.itheima.domain.Order">
    <result property="id" column="id"></result>
    <result property="ordertime" column="ordertime"></result>
    <result property="total" column="total"></result>
    <association property="user" javaType="com.itheima.domain.User">
        <result column="uid" property="id"></result>
        <result column="username" property="username"></result>
        <result column="password" property="password"></result>
        <result column="birthday" property="birthday"></result>
    </association>
</resultMap>
    1.1.6 测试结果
    OrderMapper mapper = sqlSession.getMapper(OrderMapper.class);
List<Order> all = mapper.findAll();
for(Order order : all){
    System.out.println(order);
}

    图片3

    1.2 一对多查询

    1.2.1 一对多查询的模型

    用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

    一对多查询的需求：查询一个用户，与此同时查询出该用户具有的订单

    图片4

    1.2.2 一对多查询的语句

    对应的sql语句：select *,o.id oid from user u left join orders o on u.id=o.uid;

    查询的结果如下：

    图片5

    1.2.3 修改User实体
    public class Order {

    private int id;
    private Date ordertime;
    private double total;

    //代表当前订单从属于哪一个客户
    private User user;
}

public class User {
    
    private int id;
    private String username;
    private String password;
    private Date birthday;
    //代表当前用户具备哪些订单
    private List<Order> orderList;
}
    1.2.4 创建UserMapper接口
    public interface UserMapper {
    List<User> findAll();
}
    1.2.5 配置UserMapper.xml
    <mapper namespace="com.itheima.mapper.UserMapper">
    <resultMap id="userMap" type="com.itheima.domain.User">
        <result column="id" property="id"></result>
        <result column="username" property="username"></result>
        <result column="password" property="password"></result>
        <result column="birthday" property="birthday"></result>
        <collection property="orderList" ofType="com.itheima.domain.Order">
            <result column="oid" property="id"></result>
            <result column="ordertime" property="ordertime"></result>
            <result column="total" property="total"></result>
        </collection>
    </resultMap>
    <select id="findAll" resultMap="userMap">
        select *,o.id oid from user u left join orders o on u.id=o.uid
    </select>
</mapper>
    1.2.6 测试结果
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> all = mapper.findAll();
for(User user : all){
    System.out.println(user.getUsername());
    List<Order> orderList = user.getOrderList();
    for(Order order : orderList){
        System.out.println(order);
    }
    System.out.println("----------------------------------");
}

    图片6

    1.3 多对多查询

    1.3.1 多对多查询的模型

    用户表和角色表的关系为，一个用户有多个角色，一个角色被多个用户使用

    多对多查询的需求：查询用户同时查询出该用户的所有角色

    图片7

    1.3.2 多对多查询的语句

    对应的sql语句：select u.,r.,r.id rid from user u left join user_role ur on u.id=ur.user_id

    inner join role r on ur.role_id=r.id;

    查询的结果如下：

    图片8

    1.3.3 创建Role实体，修改User实体
    public class User {
    private int id;
    private String username;
    private String password;
    private Date birthday;
    //代表当前用户具备哪些订单
    private List<Order> orderList;
    //代表当前用户具备哪些角色
    private List<Role> roleList;
}

public class Role {

    private int id;
    private String rolename;

}
    1.3.4 添加UserMapper接口方法
    List<User> findAllUserAndRole();
    1.3.5 配置UserMapper.xml
    <resultMap id="userRoleMap" type="com.itheima.domain.User">
    <result column="id" property="id"></result>
    <result column="username" property="username"></result>
    <result column="password" property="password"></result>
    <result column="birthday" property="birthday"></result>
    <collection property="roleList" ofType="com.itheima.domain.Role">
        <result column="rid" property="id"></result>
        <result column="rolename" property="rolename"></result>
    </collection>
</resultMap>
<select id="findAllUserAndRole" resultMap="userRoleMap">
    select u.*,r.*,r.id rid from user u left join user_role ur on u.id=ur.user_id
    inner join role r on ur.role_id=r.id
</select>
    1.3.6 测试结果
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> all = mapper.findAllUserAndRole();
for(User user : all){
    System.out.println(user.getUsername());
    List<Role> roleList = user.getRoleList();
    for(Role role : roleList){
        System.out.println(role);
    }
    System.out.println("----------------------------------");
}

    图片9

    1.4 知识小结

    MyBatis多表配置方式：

    一对一配置：使用做配置

    一对多配置：使用+做配置

    多对多配置：使用+做配置

    2.Mybatis的注解开发

    2.1 MyBatis的常用注解

    这几年来注解开发越来越流行，Mybatis也可以使用注解开发方式，这样我们就可以减少编写Mapper

    映射文件了。我们先围绕一些基本的CRUD来学习，再学习复杂映射多表操作。

    @Insert：实现新增

    @Update：实现更新

    @Delete：实现删除

    @Select：实现查询

    @Result：实现结果集封装

    @Results：可以与@Result 一起使用，封装多个结果集

    @One：实现一对一结果集封装

    @Many：实现一对多结果集封装

    2.2 MyBatis的增删改查

    我们完成简单的user表的增删改查的操作

    private UserMapper userMapper;

@Before
public void before() throws IOException {
    InputStream resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");
    SqlSessionFactory sqlSessionFactory = new 
                 SqlSessionFactoryBuilder().build(resourceAsStream);
    SqlSession sqlSession = sqlSessionFactory.openSession(true);
    userMapper = sqlSession.getMapper(UserMapper.class);
}

@Test
public void testAdd() {
    User user = new User();
    user.setUsername("测试数据");
    user.setPassword("123");
    user.setBirthday(new Date());
    userMapper.add(user);
}
@Test
public void testUpdate() throws IOException {
    User user = new User();
    user.setId(16);
    user.setUsername("测试数据修改");
    user.setPassword("abc");
    user.setBirthday(new Date());
    userMapper.update(user);
}

@Test
public void testDelete() throws IOException {
    userMapper.delete(16);
}
@Test
public void testFindById() throws IOException {
    User user = userMapper.findById(1);
    System.out.println(user);
}
@Test
public void testFindAll() throws IOException {
    List<User> all = userMapper.findAll();
    for(User user : all){
        System.out.println(user);
    }
}

    修改MyBatis的核心配置文件，我们使用了注解替代的映射文件，所以我们只需要加载使用了注解的Mapper接口即可

    <mappers>
    <!--扫描使用注解的类-->
    <mapper class="com.itheima.mapper.UserMapper"></mapper>
</mappers>

    或者指定扫描包含映射关系的接口所在的包也可以

    <mappers>
    <!--扫描使用注解的类所在的包-->
    <package name="com.itheima.mapper"></package>
</mappers>

    2.3 MyBatis的注解实现复杂映射开发

    实现复杂关系映射之前我们可以在映射文件中通过配置来实现，使用注解开发后，我们可以使用@Results注解，@Result注解，@One注解，@Many注解组合完成复杂关系的配置

    图片10

    图片11

    2.4 一对一查询

    2.4.1 一对一查询的模型

    用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

    一对一查询的需求：查询一个订单，与此同时查询出该订单所属的用户

    图片12

    2.4.2 一对一查询的语句

    对应的sql语句：

    select * from orders;

select * from user where id=查询出订单的uid;

    查询的结果如下：

    图片13

    2.4.3 创建Order和User实体
    public class Order {

    private int id;
    private Date ordertime;
    private double total;

    //代表当前订单从属于哪一个客户
    private User user;
}

public class User {
    
    private int id;
    private String username;
    private String password;
    private Date birthday;

}
    2.4.4 创建OrderMapper接口
    public interface OrderMapper {
    List<Order> findAll();
}
    2.4.5 使用注解配置Mapper
    public interface OrderMapper {
    @Select("select * from orders")
    @Results({
            @Result(id=true,property = "id",column = "id"),
            @Result(property = "ordertime",column = "ordertime"),
            @Result(property = "total",column = "total"),
            @Result(property = "user",column = "uid",
                    javaType = User.class,
                    one = @One(select = "com.itheima.mapper.UserMapper.findById"))
    })
    List<Order> findAll();
}

    public interface UserMapper {

    @Select("select * from user where id=#{id}")
    User findById(int id);
    
}
    2.4.6 测试结果
    @Test
public void testSelectOrderAndUser() {
    List<Order> all = orderMapper.findAll();
    for(Order order : all){
        System.out.println(order);
    }
}

    图片14

    2.5 一对多查询

    2.5.1 一对多查询的模型

    用户表和订单表的关系为，一个用户有多个订单，一个订单只从属于一个用户

    一对多查询的需求：查询一个用户，与此同时查询出该用户具有的订单

    图片15

    2.5.2 一对多查询的语句

    对应的sql语句：

    select * from user;

select * from orders where uid=查询出用户的id;

    查询的结果如下：

    图片16

    2.5.3 修改User实体
    public class Order {

    private int id;
    private Date ordertime;
    private double total;

    //代表当前订单从属于哪一个客户
    private User user;
}

public class User {
    
    private int id;
    private String username;
    private String password;
    private Date birthday;
    //代表当前用户具备哪些订单
    private List<Order> orderList;
}
    2.5.4 创建UserMapper接口
    List<User> findAllUserAndOrder();
    2.5.5 使用注解配置Mapper
    public interface UserMapper {
    @Select("select * from user")
    @Results({
            @Result(id = true,property = "id",column = "id"),
            @Result(property = "username",column = "username"),
            @Result(property = "password",column = "password"),
            @Result(property = "birthday",column = "birthday"),
            @Result(property = "orderList",column = "id",
                    javaType = List.class,
                    many = @Many(select = "com.itheima.mapper.OrderMapper.findByUid"))
    })
    List<User> findAllUserAndOrder();
}

public interface OrderMapper {
    @Select("select * from orders where uid=#{uid}")
    List<Order> findByUid(int uid);

}
    2.5.6 测试结果
    List<User> all = userMapper.findAllUserAndOrder();
for(User user : all){
    System.out.println(user.getUsername());
    List<Order> orderList = user.getOrderList();
    for(Order order : orderList){
        System.out.println(order);
    }
    System.out.println("-----------------------------");
}

    图片17

    2.6 多对多查询

    2.6.1 多对多查询的模型

    用户表和角色表的关系为，一个用户有多个角色，一个角色被多个用户使用

    多对多查询的需求：查询用户同时查询出该用户的所有角色

    图片18

    2.6.2 多对多查询的语句

    对应的sql语句：

    select * from user;

select * from role r,user_role ur where r.id=ur.role_id and ur.user_id=用户的id

    查询的结果如下：

    图片19

    2.6.3 创建Role实体，修改User实体
    public class User {
    private int id;
    private String username;
    private String password;
    private Date birthday;
    //代表当前用户具备哪些订单
    private List<Order> orderList;
    //代表当前用户具备哪些角色
    private List<Role> roleList;
}

public class Role {

    private int id;
    private String rolename;

}
    2.6.4 添加UserMapper接口方法
    List<User> findAllUserAndRole();
    2.6.5 使用注解配置Mapper
    public interface UserMapper {
    @Select("select * from user")
    @Results({
        @Result(id = true,property = "id",column = "id"),
        @Result(property = "username",column = "username"),
        @Result(property = "password",column = "password"),
        @Result(property = "birthday",column = "birthday"),
        @Result(property = "roleList",column = "id",
                javaType = List.class,
                many = @Many(select = "com.itheima.mapper.RoleMapper.findByUid"))
})
List<User> findAllUserAndRole();}



public interface RoleMapper {
    @Select("select * from role r,user_role ur where r.id=ur.role_id and ur.user_id=#{uid}")
    List<Role> findByUid(int uid);
}
    2.6.6 测试结果
    UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> all = mapper.findAllUserAndRole();
for(User user : all){
    System.out.println(user.getUsername());
    List<Role> roleList = user.getRoleList();
    for(Role role : roleList){
        System.out.println(role);
    }
    System.out.println("----------------------------------");
}

    图片20

    SSM框架整合

    1.1 原始方式整合

    1.准备工作

    7

    2.创建Maven工程

    8

    3.导入Maven坐标

    参考：素材/配置文件/pom.xml文件

    4.编写实体类
    public class Account {
    private int id;
    private String name;
    private double money;
    //省略getter和setter方法
}
    5.编写Mapper接口
    public interface AccountMapper {
    //保存账户数据
    void save(Account account);
    //查询账户数据
    List<Account> findAll();
}
    6.编写Service接口
    public interface AccountService {
    void save(Account account); //保存账户数据
    List<Account> findAll(); //查询账户数据
}
    7.编写Service接口实现
    @Service("accountService")
public class AccountServiceImpl implements AccountService {
    public void save(Account account) {
        SqlSession sqlSession = MyBatisUtils.openSession();
        AccountMapper accountMapper = sqlSession.getMapper(AccountMapper.class);
        accountMapper.save(account);
        sqlSession.commit();
        sqlSession.close();
    }
    public List<Account> findAll() {
        SqlSession sqlSession = MyBatisUtils.openSession();
        AccountMapper accountMapper = sqlSession.getMapper(AccountMapper.class);
        return accountMapper.findAll();
    }
}
    8.编写Controller
    @Controller
public class AccountController {
    @Autowired
    private AccountService accountService;
    @RequestMapping("/save")
    @ResponseBody
    public String save(Account account){
        accountService.save(account);
        return "save success";
    }
    @RequestMapping("/findAll")
    public ModelAndView findAll(){
        ModelAndView modelAndView = new ModelAndView();
        modelAndView.setViewName("accountList");
        modelAndView.addObject("accountList",accountService.findAll());
        return modelAndView;
    }
}
    9.编写添加页面
    <%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h1>保存账户信息表单</h1>
    <form action="${pageContext.request.contextPath}/save.action" method="post">
        用户名称<input type="text" name="name"><br/>
        账户金额<input type="text" name="money"><br/>
        <input type="submit" value="保存"><br/>
    </form>
</body>
</html>
    10.编写列表页面
    <table border="1">
    <tr>
        <th>账户id</th>
        <th>账户名称</th>
        <th>账户金额</th>
    </tr>
    <c:forEach items="${accountList}" var="account">
        <tr>
            <td>${account.id}</td>
            <td>${account.name}</td>
            <td>${account.money}</td>
        </tr>
    </c:forEach>
</table>
    11.编写相应配置文件(文件参考目录：素材/配置文件)

    •Spring配置文件：applicationContext.xml

    •SprngMVC配置文件：spring-mvc.xml

    •MyBatis映射文件：AccountMapper.xml

    •MyBatis核心文件：sqlMapConfig.xml

    •数据库连接信息文件：jdbc.properties

    •Web.xml文件：web.xml

    •日志文件：[log4j.xml](

    12.测试添加账户

    9

    13.测试账户列表

    10

    1.2 Spring整合MyBatis

    1.整合思路

    11

    2.将SqlSessionFactory配置到Spring容器中
    <!--加载jdbc.properties-->
<context:property-placeholder location="classpath:jdbc.properties"/>
<!--配置数据源-->
<bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource">
    <property name="driverClass" value="${jdbc.driver}"/>
    <property name="jdbcUrl" value="${jdbc.url}"/>
    <property name="user" value="${jdbc.username}"/>
    <property name="password" value="${jdbc.password}"/>
</bean>
<!--配置MyBatis的SqlSessionFactory-->
<bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean">
    <property name="dataSource" ref="dataSource"/>
    <property name="configLocation" value="classpath:sqlMapConfig.xml"/>
</bean>
    3.扫描Mapper，让Spring容器产生Mapper实现类
    <!--配置Mapper扫描-->
<bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
    <property name="basePackage" value="com.itheima.mapper"/>
</bean>
    4.配置声明式事务控制
    <!--配置声明式事务控制-->
<bean id="transacionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
    <property name="dataSource" ref="dataSource"/>
</bean>
<tx:advice id="txAdvice" transaction-manager="transacionManager">
    <tx:attributes>
        <tx:method name="*"/>
    </tx:attributes>
</tx:advice>
<aop:config>
    <aop:pointcut id="txPointcut" expression="execution(* com.itheima.service.impl.*.*(..))"/>
    <aop:advisor advice-ref="txAdvice" pointcut-ref="txPointcut"/>
</aop:config>
    5.修改Service实现类代码
    @Service("accountService")
public class AccountServiceImpl implements AccountService {

    @Autowired
    private AccountMapper accountMapper;

    public void save(Account account) {
        accountMapper.save(account);
    }
    public List<Account> findAll() {
        return accountMapper.findAll();
    }
}
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  • 原文地址：https://www.cnblogs.com/coderD/p/13799166.html
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