MyBatis从入门到精通—MyBatis多表查询和注解开发

Posted 2022-07-15 共饮一杯无

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Mybatis多表查询

一对一查询

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

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：

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;

创建OrderMapper接口

public interface OrderMapper 
    List<Order> findAll();

配置OrderMapper.xml

<mapper namespace="com.zjq.mapper.OrderMapper">
    <resultMap id="orderMap" type="com.zjq.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.zjq.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.zjq.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>

测试结果

OrderMapper mapper = sqlSession.getMapper(OrderMapper.class);
List<Order> all = mapper.findAll();
for(Order order : all)
    System.out.println(order);

输出：

11:29:37,682 DEBUG JdbcTransaction:137 - Opening JDBC Connection
11:29:38,178 DEBUG PooledDataSource:406 - Created connection 1858609436.
11:29:38,179 DEBUG JdbcTransaction:101 - Setting autocommit to false on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c]
11:29:38,182 DEBUG findAll:159 - ==>  Preparing: SELECT *,o.id oid FROM orders o,USER u WHERE o.uid=u.id 
11:29:38,305 DEBUG findAll:159 - ==> Parameters: 
11:29:38,351 DEBUG findAll:159 - <==      Total: 3
11:29:38,357 DEBUG JdbcTransaction:123 - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c]
Orderid=1, ordertime=Sun Dec 12 00:00:00 GMT+08:00 2021, total=3000.0, user=Userid=1, username=zjq, password=abc, birthday=Wed Jul 28 00:00:00 GMT+08:00 2021, roleList=null
Orderid=2, ordertime=Sun Dec 12 00:00:00 GMT+08:00 2021, total=4000.0, user=Userid=1, username=zjq, password=abc, birthday=Wed Jul 28 00:00:00 GMT+08:00 2021, roleList=null
Orderid=3, ordertime=Sun Dec 12 00:00:00 GMT+08:00 2021, total=5000.0, user=Userid=2, username=jack, password=123456, birthday=Fri Aug 20 00:00:00 GMT+08:00 2021, roleList=null

一对多查询

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

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：

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;

创建UserMapper接口

public interface UserMapper 
    List<User> findAll();

配置UserMapper.xml

<mapper namespace="com.zjq.mapper.UserMapper">
    <resultMap id="userMap" type="com.zjq.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.zjq.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>

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("----------------------------------");

输出：

11:38:28,060 DEBUG findAll:159 - ==>  Preparing: SELECT *,o.id oid FROM USER u,orders o WHERE u.id=o.uid 
11:38:28,179 DEBUG findAll:159 - ==> Parameters: 
11:38:28,254 DEBUG findAll:159 - <==      Total: 3
Userid=1, username=zjq, password=abc, birthday=Wed Jul 28 00:00:00 GMT+08:00 2021, roleList=null
Userid=2, username=jack, password=123456, birthday=Fri Aug 20 00:00:00 GMT+08:00 2021, roleList=null
11:38:28,265 DEBUG JdbcTransaction:123 - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c]
11:38:28,265 DEBUG JdbcTransaction:91 - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c]
11:38:28,265 DEBUG PooledDataSource:363 - Returned connection 1858609436 to pool.

多对多查询

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

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 sys_user_role ur on u.id=ur.userid

inner join sys_role r on ur.roleid=r.id;

查询的结果如下：

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;

添加UserMapper接口方法

List<User> findAllUserAndRole();

配置UserMapper.xml

<resultMap id="userRoleMap" type="com.zjq.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.zjq.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 sys_user_role ur on u.id=ur.userid
    inner join sys_role r on ur.roleid=r.id;
</select>

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("----------------------------------");

11:45:51,443 DEBUG findUserAndRoleAll:159 - ==>  Preparing: SELECT * FROM USER u,sys_user_role ur,sys_role r WHERE u.id=ur.userId AND ur.roleId=r.id 
11:45:51,572 DEBUG findUserAndRoleAll:159 - ==> Parameters: 
Userid=1, username=zjq, password=abc, birthday=Wed Jul 28 00:00:00 GMT+08:00 2021, roleList=[Roleid=1, roleName=CTO, roleDesc=CTO, Roleid=2, roleName=COO, roleDesc=COO]
Userid=2, username=jack, password=123456, birthday=Fri Aug 20 00:00:00 GMT+08:00 2021, roleList=[Roleid=1, roleName=CTO, roleDesc=CTO, Roleid=2, roleName=COO, roleDesc=COO]
11:45:51,610 DEBUG findUserAndRoleAll:159 - <==      Total: 4
11:45:51,618 DEBUG JdbcTransaction:123 - Resetting autocommit to true on JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c]
11:45:51,619 DEBUG JdbcTransaction:91 - Closing JDBC Connection [com.mysql.jdbc.JDBC4Connection@6ec8211c]
11:45:51,619 DEBUG PooledDataSource:363 - Returned connection 1858609436 to pool.

Mybatis的注解开发

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

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.zjq.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.zjq.mapper"></package>
</mappers>

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

一对一查询

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

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;

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;

创建OrderMapper接口

public interface OrderMapper 
    List<Order> findAll();

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.zjq.mapper.UserMapper.findById"))
    )
    List<Order> findAll();

public interface UserMapper 

    @Select("select * from user where id=#id")
    User findById(int id);

测试结果

@Test
public void testSelectOrderAndUser() 
    List<Order> all = orderMapper.findAll();
    for(Order order : all)
        System.out.println(order);

一对多查询

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

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;

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;

创建UserMapper接口

List<User> findAllUserAndOrder();

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.zjq.mapper.OrderMapper.findByUid"))
    )
    List<User> findAllUserAndOrder();


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

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("-----------------------------");

多对多查询

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

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

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;

添加UserMapper接口方法

List<User> findAllUserAndRole();

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.zjq.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);

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("----------------------------------");

SSM框架整合

1.1 原始方式整合

1.准备工作

2.创建Maven工程

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>
    保存账户信息表单
    <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

13.测试账户列表

1.2 Spring整合MyBatis

1.整合思路

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.zjq.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.zjq.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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