Mybatis的注解開發(fā)

MyBatis的常用注解

這幾年來(lái)注解開發(fā)越來(lái)越流行，Mybatis也可以使用注解開發(fā)方式，這樣我們就可以減少編寫Mapper映射文件了。

@Insert：實(shí)現(xiàn)新增

@Update：實(shí)現(xiàn)更新

@Delete：實(shí)現(xiàn)刪除

@Select：實(shí)現(xiàn)查詢

@Result：實(shí)現(xiàn)結(jié)果集封裝

@Results：可以與@Result 一起使用，封裝多個(gè)結(jié)果集

@One：實(shí)現(xiàn)一對(duì)一結(jié)果集封裝

@Many：實(shí)現(xiàn)一對(duì)多結(jié)果集封裝

MyBatis的增刪改查

我們完成簡(jiǎn)單的user表的增刪改查的操作
修改MyBatis的核心配置文件，我們使用了注解替代的映射文件，所以我們只需要加載使用了注解的Mapper接口即可

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

或者指定掃描包含映射關(guān)系的接口所在的包也可以

<mappers><!--掃描使用注解的類所在的包--><package name="com.itheima.mapper"></package> </mappers> userMapper mapper;@Beforepublic void before(){InputStream resourceAsStream = null;try {resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");} catch (IOException ioException) {ioException.printStackTrace();}SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(resourceAsStream);SqlSession sqlSession = sqlSessionFactory.openSession(true);mapper = sqlSession.getMapper(userMapper.class);}@Testpublic void tset4() {User user = new User();user.setUsername("cx");user.setPassword("159");mapper.add(user);}@Testpublic void tset5() {mapper.delete(5);}@Testpublic void tset6() {User user = new User();user.setId(4);user.setPassword("159");mapper.update(user);}@Testpublic void tset7() {System.out.println(mapper.findById(1));} public interface userMapper {@Select(" select * from user")public List<User> findAll();@Select("select * from user where id=#{id}")public User findById(int i);@Insert(" insert into user values (#{id},#{username},#{password},#{birthday})")public void add(User user);@Update(" update user set password=#{password} where id=#{id}")public void update(User user);@Delete("delete from user where id=#{id}")public void delete(int i);}

MyBatis的注解實(shí)現(xiàn)復(fù)雜映射開發(fā)

實(shí)現(xiàn)復(fù)雜關(guān)系映射之前我們可以在映射文件中通過(guò)配置來(lái)實(shí)現(xiàn)，使用注解開發(fā)后，我們可以使用@Results注解，@Result注解，@One注解，@Many注解組合完成復(fù)雜關(guān)系的配置

一對(duì)一查詢

一對(duì)一查詢的模型

用戶表和訂單表的關(guān)系為，一個(gè)用戶有多個(gè)訂單，一個(gè)訂單只從屬于一個(gè)用戶

一對(duì)一查詢的需求：查詢一個(gè)訂單，與此同時(shí)查詢出該訂單所屬的用戶

創(chuàng)建Order和User實(shí)體

public class Order {private int id;private Date ordertime;private double total;//代表當(dāng)前訂單從屬于哪一個(gè)客戶private User user; }public class User {private int id;private String username;private String password;private Date birthday;}

創(chuàng)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(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.controller.userMapper.findById"))})List<Order> findAll(); }

測(cè)試結(jié)果

@Testpublic void tset3() {InputStream resourceAsStream = null;try {resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");} catch (IOException ioException) {ioException.printStackTrace();}SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(resourceAsStream);SqlSession sqlSession = sqlSessionFactory.openSession(true);OrderMapper mapper = sqlSession.getMapper(OrderMapper.class);System.out.println(mapper.findAll());}

一對(duì)多查詢

一對(duì)多查詢的模型

用戶表和訂單表的關(guān)系為，一個(gè)用戶有多個(gè)訂單，一個(gè)訂單只從屬于一個(gè)用戶

一對(duì)多查詢的需求：查詢一個(gè)用戶，與此同時(shí)查詢出該用戶具有的訂單

修改User實(shí)體

public class Order {private int id;private Date ordertime;private double total;//代表當(dāng)前訂單從屬于哪一個(gè)客戶private User user; }public class User {private int id;private String username;private String password;private Date birthday;//代表當(dāng)前用戶具備哪些訂單private List<Order> orderList; }

創(chuàng)建UserMapper接口

List<User> findAllUserAndOrder();

使用注解配置Mapper

@Select( "select * from user")@Results({@Result(property = "username" ,column = "username"),@Result(property = "password",column = "password"),@Result(property = "birthday" ,column = "birthday"),@Result(id=true,property = "id",column = "id"),@Result(property = "orderList",column = "id",javaType = List.class,many = @Many(select = "com.controller.OrderMapper.findByUid"))})public List<User> findAllUserAndOrder(); @Select("select * from orders where uid=#{uid}")Order findByUid(int i);

測(cè)試結(jié)果

userMapper mapper;@Beforepublic void before(){InputStream resourceAsStream = null;try {resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");} catch (IOException ioException) {ioException.printStackTrace();}SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(resourceAsStream);SqlSession sqlSession = sqlSessionFactory.openSession(true);mapper = sqlSession.getMapper(userMapper.class);} @Testpublic void tset7() {System.out.println(mapper.findAllUserAndOrder());}

多對(duì)多查詢

多對(duì)多查詢的模型

用戶表和角色表的關(guān)系為，一個(gè)用戶有多個(gè)角色，一個(gè)角色被多個(gè)用戶使用

多對(duì)多查詢的需求：查詢用戶同時(shí)查詢出該用戶的所有角色

public class User {private int id;private String username;private String password;private Date birthday;//代表當(dāng)前用戶具備哪些訂單private List<Order> orderList;//代表當(dāng)前用戶具備哪些角色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

@Select( "select * from user")@Results({@Result(property = "username" ,column = "username"),@Result(property = "password",column = "password"),@Result(property = "birthday" ,column = "birthday"),@Result(id=true,property = "id",column = "id"),@Result(property = "roleList",column = "id",javaType = List.class,many = @Many(select = "com.controller.RoleMapper.findById"))})public List<User> findAllUserAndRole(); public interface RoleMapper {@Select("select r.* from sys_user_role ur,sys_role r where ur.roleid=r.id and #{id}=ur.userid")List<Role> findById(int i); }

測(cè)試結(jié)果

@Beforepublic void before(){InputStream resourceAsStream = null;try {resourceAsStream = Resources.getResourceAsStream("SqlMapConfig.xml");} catch (IOException ioException) {ioException.printStackTrace();}SqlSessionFactory sqlSessionFactory=new SqlSessionFactoryBuilder().build(resourceAsStream);SqlSession sqlSession = sqlSessionFactory.openSession(true);mapper = sqlSession.getMapper(userMapper.class);}@Testpublic void tset7() {System.out.println(mapper.findAllUserAndRole());}

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