22mybaits注解开发

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。

1.常用注解说明

@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
@ResultMap:实现引用@Results 定义的封装
@One:实现一对一结果集封装
@Many:实现一对多结果集封装
@SelectProvider: 实现动态 SQL 映射
@CacheNamespace:实现注解二级缓存的使用

2.使用Mybatis注解实现基本CRUD

2.1查询数据库

 

 

2.2创建maven工程导入jar包的坐标

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.itheima</groupId>
    <artifactId>day04_eesy_03annotation_mybaitis</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>jar</packaging>
    <dependencies>
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.4.5</version>
        </dependency>
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
            <version>5.1.6</version>
        </dependency>
        <dependency>
            <groupId>log4j</groupId>
            <artifactId>log4j</artifactId>
            <version>1.2.12</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.10</version>
        </dependency>
    </dependencies>

</project>

2.3配置数据库连接信息

jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/eesy_mybatis
jdbc.username=root
jdbc.password=123456

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration
        PUBLIC "-//mybatis.org//DTD Config 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <!-- 引入外部配置文件-->
    <properties resource="jdbcConfig.properties"></properties>
    <!--配置别名-->
    <typeAliases>
        <package name="com.itheima.domain"></package>
    </typeAliases>
    <!--配置环境-->
    <environments default="mysql">
        <environment id="mysql">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"></property>
                <property name="url" value="${jdbc.url}"></property>
                <property name="username" value="${jdbc.username}"></property>
                <property name="password" value="${jdbc.password}"></property>
            </dataSource>
        </environment>
    </environments>
    <!-- 指定带有注解的dao接口所在位置 -->
    <mappers>
        <mapper class="com.itheima.dao.IUserDao"></mapper>
    </mappers>
</configuration>

2.4编写实体类

package com.itheima.domain;

import java.io.Serializable;
import java.util.Date;

public class User implements Serializable {

    private Integer id;
    private String username;
    private String address;
    private String sex;
    private Date birthday;

    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 getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }

    public Date getBirthday() {
        return birthday;
    }

    public void setBirthday(Date birthday) {
        this.birthday = birthday;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", address='" + address + '\'' +
                ", sex='" + sex + '\'' +
                ", birthday=" + birthday +
                '}';
    }
}

2.5使用注解方式开发持久层接口

package com.itheima.dao;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.Select;

import java.util.List;

/**
 * @Select @Insert @Update @Delete
 */
public interface IUserDao {
    /**
     * 查询所有用户
     * @return
     */
    @Select("select * from user")
    List<User> findAll();
}

2.6编写测试方法

package com.itheima.test;

import com.itheima.dao.IUserDao;
import com.itheima.domain.User;
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 java.io.InputStream;
import java.util.List;

public class MybatisAnnoTest {

    /**
     * 测试基于注解的mybatis使用
     * @param args
     */
    public static void main(String[] args) throws  Exception{
        //1.获取字节输入流
        InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
        //2.根据字节输入流构建SqlSessionFactory
        SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(in);
        //3.根据SqlSessionFactory生产一个SqlSession
        SqlSession session = factory.openSession();
        //4.使用SqlSession获取Dao的代理对象
        IUserDao userDao = session.getMapper(IUserDao.class);
        //5.执行Dao的方法
        List<User> users = userDao.findAll();
        for(User user : users){
            System.out.println(user);
        }
        //6.释放资源
        session.close();
        in.close();
    }
}

 

 

2.7CURD

package com.itheima.dao;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;

import java.util.List;

/**
 * @Select @Insert @Update @Delete
 */
public interface IUserDao {
    /**
     * 查询所有用户
     *
     * @return
     */
    @Select("select * from user")
    List<User> findAll();

    /**
     * 保存用户
     *
     * @param user
     */
    @Insert("insert into user(username,address,sex,birthday)values(#{username},#{address},#{sex},#{birthday})")
    void saveUser(User user);

    @Update("update user set username=#{username},sex=#{sex},birthday=#{birthday},address=#{address} where id=#{id}")
    void updateUser(User user);

    @Delete("delete from user where id=#{id} ")
    void deleteUser(Integer userId);

    @Select("select * from user  where id=#{id} ")
    User findById(Integer userId);

    @Select("select * from user where username like #{username} ")
    List<User> findUserByName(String username);

    @Select("select count(*) from user ")
    int findTotalUser();

}

package com.itheima.test;

import com.itheima.dao.IUserDao;
import com.itheima.domain.User;
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.After;
import org.junit.Before;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

public class AnnotationCRUDTest {
    private InputStream in;
    private SqlSessionFactory factory;
    private SqlSession session;
    private IUserDao userDao;

    @Before
    public void init() throws Exception {
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        factory = new SqlSessionFactoryBuilder().build(in);
        session = factory.openSession();
        userDao = session.getMapper(IUserDao.class);

    }

    @After
    public void destroy() throws Exception {
        session.commit();
        session.close();
        in.close();
    }

    @Test
    public void testSave() {
        User user = new User();
        user.setUsername("mybatis annotation");
        user.setAddress("nanchang");
        userDao.saveUser(user);
    }

    @Test
    public void testUpdate() {
        User user = new User();
        user.setId(60);
        user.setUsername("mybatis annotation");
        user.setAddress("nanchang");
        user.setSex("男");
        userDao.updateUser(user);
    }

    @Test
    public void testDelete() {
        userDao.deleteUser(60);
    }

    @Test
    public void testFindOne() {
        User user = userDao.findById(58);
        System.out.println(user);
    }

    @Test
    public void testFindByName() {
        List<User> users = userDao.findUserByName("%mybatis%");
        for (User user : users) {
            System.out.println(user);
        }
    }

    @Test
    public  void testFindTotal(){
        int total = userDao.findTotalUser();
        System.out.println(total);
    }

}

3.在注解配置中解决数据库字段名和实体类字段名不对应问题

package com.itheima.domain;

import java.io.Serializable;
import java.util.Date;
import java.util.List;

public class User implements Serializable {

    private Integer userId;
    private String userName;
    private String userAddress;
    private String userSex;
    private Date userBirthday;

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserAddress() {
        return userAddress;
    }

    public void setUserAddress(String userAddress) {
        this.userAddress = userAddress;
    }

    public String getUserSex() {
        return userSex;
    }

    public void setUserSex(String userSex) {
        this.userSex = userSex;
    }

    public Date getUserBirthday() {
        return userBirthday;
    }

    public void setUserBirthday(Date userBirthday) {
        this.userBirthday = userBirthday;
    }

    @Override
    public String toString() {
        return "User{" +
                "userId=" + userId +
                ", userName='" + userName + '\'' +
                ", userAddress='" + userAddress + '\'' +
                ", userSex='" + userSex + '\'' +
                ", userBirthday=" + userBirthday +
                '}';
    }
}

 

 

package com.itheima.dao;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

/**
 * @Select @Insert @Update @Delete
 */
public interface IUserDao {

    /**
     * 查询所有用户
     *
     * @return
     */
    @Select("select * from user")
    @Results(id="userMap",value= {
            @Result(id = true, column = "id", property = "userId"),
            @Result(column = "username", property = "userName"),
            @Result(column = "address", property = "userAddress"),
            @Result(column = "sex", property = "userSex"),
            @Result(column = "birthday", property = "userBirthday")
    })
    List<User> findAll();


    /**
     * 根据id查询用户
     *
     * @param userId
     * @return
     */
    @Select("select * from user  where id=#{id} ")
//    @ResultMap(value = {"userMap"})
    @ResultMap("userMap")
    User findById(Integer userId);

    /**
     * 根据用户名称模糊查询
     *
     * @param username
     * @return
     */
    @Select("select * from user where username like #{username} ")
    List<User> findUserByName(String username);

}

4.多表1对1查询

4.1实体类

package com.itheima.domain;

import java.io.Serializable;
import java.util.Date;
import java.util.List;

public class User implements Serializable {

    private Integer userId;
    private String userName;
    private String userAddress;
    private String userSex;
    private Date userBirthday;

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserAddress() {
        return userAddress;
    }

    public void setUserAddress(String userAddress) {
        this.userAddress = userAddress;
    }

    public String getUserSex() {
        return userSex;
    }

    public void setUserSex(String userSex) {
        this.userSex = userSex;
    }

    public Date getUserBirthday() {
        return userBirthday;
    }

    public void setUserBirthday(Date userBirthday) {
        this.userBirthday = userBirthday;
    }

    @Override
    public String toString() {
        return "User{" +
                "userId=" + userId +
                ", userName='" + userName + '\'' +
                ", userAddress='" + userAddress + '\'' +
                ", userSex='" + userSex + '\'' +
                ", userBirthday=" + userBirthday +
                '}';
    }
}

package com.itheima.domain;

import java.io.Serializable;

public class Account implements Serializable {

    private Integer id;
    private Integer uid;
    private Double money;

    //多对一（mybatis中称之为一对一）的映射：一个账户只能属于一个用户
    private User user;

    public User getUser() {
        return user;
    }

    public void setUser(User user) {
        this.user = user;
    }

    public Integer getId() {
        return id;
    }

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

    public Integer getUid() {
        return uid;
    }

    public void setUid(Integer uid) {
        this.uid = uid;
    }

    public Double getMoney() {
        return money;
    }

    public void setMoney(Double money) {
        this.money = money;
    }

    @Override
    public String toString() {
        return "Account{" +
                "id=" + id +
                ", uid=" + uid +
                ", money=" + money +
                '}';
    }
}

4.2添加账户的持久层接口并使用注解配置

package com.itheima.dao;

import com.itheima.domain.Account;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.mapping.FetchType;

import java.util.List;

public interface IAccountDao {

    /**
     * 查询所有账户，并且获取每个账户所属的用户信息
     * @return
     */
    @Select("select * from account")
    @Results(id="accountMap",value = {
            @Result(id=true,column = "id",property = "id"),
            @Result(column = "uid",property = "uid"),
            @Result(column = "money",property = "money"),
            @Result(property = "user",column = "uid",one=@One(select="com.itheima.dao.IUserDao.findById",fetchType= FetchType.EAGER))
    })
    List<Account> findAll();

    /**
     * 根据用户id查询账户信息
     * @param userId
     * @return
     */
    @Select("select * from account where uid = #{userId}")
    List<Account> findAccountByUid(Integer userId);
}

package com.itheima.dao;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.*;

import java.util.List;

/**
 * @Select @Insert @Update @Delete
 */
public interface IUserDao {

    /**
     * 查询所有用户
     *
     * @return
     */
    @Select("select * from user")
    @Results(id="userMap",value= {
            @Result(id = true, column = "id", property = "userId"),
            @Result(column = "username", property = "userName"),
            @Result(column = "address", property = "userAddress"),
            @Result(column = "sex", property = "userSex"),
            @Result(column = "birthday", property = "userBirthday")
    })
    List<User> findAll();


    /**
     * 根据id查询用户
     *
     * @param userId
     * @return
     */
    @Select("select * from user  where id=#{id} ")
//    @ResultMap(value = {"userMap"})
    @ResultMap("userMap")
    User findById(Integer userId);

    /**
     * 根据用户名称模糊查询
     *
     * @param username
     * @return
     */
    @Select("select * from user where username like #{username} ")
    List<User> findUserByName(String username);

}

4.3测试类

package com.itheima.test;

import com.itheima.dao.IAccountDao;
import com.itheima.domain.Account;
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.After;
import org.junit.Before;
import org.junit.Test;

import java.io.InputStream;
import java.util.List;

public class AccountTest {
    private InputStream in;
    private SqlSessionFactory factory;
    private SqlSession session;
    private IAccountDao accountDao;

    @Before
    public  void init()throws Exception{
        in = Resources.getResourceAsStream("SqlMapConfig.xml");
        factory = new SqlSessionFactoryBuilder().build(in);
        session = factory.openSession();
        accountDao = session.getMapper(IAccountDao.class);
    }

    @After
    public  void destroy()throws  Exception{
        session.commit();
        session.close();
        in.close();
    }

    @Test
    public  void  testFindAll(){
        List<Account> accounts = accountDao.findAll();
        for(Account account : accounts){
            System.out.println("----每个账户的信息-----");
            System.out.println(account);
            System.out.println(account.getUser());
        }
    }



}

5.使用注解实现一对多复杂关系映射

需求：
　　查询用户信息时，也要查询他的账户列表。使用注解方式实现。
分析：
　　一个用户具有多个账户信息，所以形成了用户(User)与账户(Account)之间的一对多关系。

5.1User实体类加入List<Account>

package com.itheima.domain;

import java.io.Serializable;
import java.util.Date;
import java.util.List;

public class User implements Serializable {

    private Integer userId;
    private String userName;
    private String userAddress;
    private String userSex;
    private Date userBirthday;
    //一对多关系映射：一个用户对应多个账户
    private List<Account> accounts;

    public List<Account> getAccounts() {
        return accounts;
    }

    public void setAccounts(List<Account> accounts) {
        this.accounts = accounts;
    }

    public Integer getUserId() {
        return userId;
    }

    public void setUserId(Integer userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getUserAddress() {
        return userAddress;
    }

    public void setUserAddress(String userAddress) {
        this.userAddress = userAddress;
    }

    public String getUserSex() {
        return userSex;
    }

    public void setUserSex(String userSex) {
        this.userSex = userSex;
    }

    public Date getUserBirthday() {
        return userBirthday;
    }

    public void setUserBirthday(Date userBirthday) {
        this.userBirthday = userBirthday;
    }

    @Override
    public String toString() {
        return "User{" +
                "userId=" + userId +
                ", userName='" + userName + '\'' +
                ", userAddress='" + userAddress + '\'' +
                ", userSex='" + userSex + '\'' +
                ", userBirthday=" + userBirthday +
                '}';
    }
}

5.2编写用户的持久层接口并使用注解配置

package com.itheima.dao;

import com.itheima.domain.User;
import org.apache.ibatis.annotations.*;
import org.apache.ibatis.mapping.FetchType;

import java.util.List;

/**
 * @Select @Insert @Update @Delete
 */
public interface IUserDao {

    /**
     * 查询所有用户
     *
     * @return
     */
    @Select("select * from user")
    @Results(id="userMap",value= {
            @Result(id = true, column = "id", property = "userId"),
            @Result(column = "username", property = "userName"),
            @Result(column = "address", property = "userAddress"),
            @Result(column = "sex", property = "userSex"),
            @Result(column = "birthday", property = "userBirthday"),
            @Result(property = "accounts",column = "id",
                    many = @Many(select = "com.itheima.dao.IAccountDao.findAccountByUid",
                            fetchType = FetchType.LAZY))
    })
    List<User> findAll();


    /**
     * 根据id查询用户
     *
     * @param userId
     * @return
     */
    @Select("select * from user  where id=#{id} ")
//    @ResultMap(value = {"userMap"})
    @ResultMap("userMap")
    User findById(Integer userId);

    /**
     * 根据用户名称模糊查询
     *
     * @param username
     * @return
     */
    @Select("select * from user where username like #{username} ")
    List<User> findUserByName(String username);

}

5.3编写账户的持久层接口并使用注解配置

package com.itheima.dao;

import com.itheima.domain.Account;
import org.apache.ibatis.annotations.One;
import org.apache.ibatis.annotations.Result;
import org.apache.ibatis.annotations.Results;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.mapping.FetchType;

import java.util.List;

public interface IAccountDao {


    /**
     * 根据用户id查询账户信息
     * @param userId
     * @return
     */
    @Select("select * from account where uid = #{userId}")
    List<Account> findAccountByUid(Integer userId);
}

5.4测试类

 @Test
    public  void findAll() {
        List<User> users = userDao.findAll();
        for (User u :users ) {
            System.out.println("每个用户的信息。。。");
            System.out.println(u);
            System.out.println(u.getAccounts());
            
        }
    }

 

 

6.mybatis基于注解的二级缓存

6.1在SqlMapConfig 

<!-- 配置二级缓存 -->
<settings>
    <!-- 开启二级缓存的支持 -->
    <setting name="cacheEnabled" value="true"/>
</settings>

6.2在持久层接口中使用注解配置二级缓存

@CacheNamespace(blocking=true)//mybatis 基于注解方式实现配置二级缓存
public interface IUserDao {}

 

来源：https://www.cnblogs.com/xinmomoyan/p/12031872.html