【MyBatis】Mybatis 注解开发

其他 2020-03-19 15:54:59 阅读次数: 0

【MyBatis】Mybatis 注解开发

1. 常用的注解说明

@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. 通过注解实现基本CRUD操作

  • 实体类（User）
package com.siyi.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 +
                '}';
    }
}
  • 主配置文件SqlMapConfig.xml
<?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"/>
    <!-- 配置别名 -->
    <typeAliases>
        <package name="com.siyi.domain"/>
    </typeAliases>
    <!-- 配置环境 -->
    <environments default="mysql">
        <environment id="mysql">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 引入带有注解的DAO接口所在位置 -->
    <mappers>
        <package name="com.siyi.dao"/>
    </mappers>
</configuration>
  • 使用注解方式开发持久层接口
package com.siyi.dao;

import com.siyi.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;

/**
 * 在mybatis中针对，CRUD一共有四个注解
 * @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})")
    public void saveUser(User user);

    /**
     * 更新用户
     * @param user
     */
    @Update("update user set username=#{username},sex=#{sex},address=#{address},birthday=#{birthday} where id=#{id}")
    public void updateUser(User user);

    /**
     * 删除用户
     * @param userId
     */
    @Delete("delete from user where id=#{id} ")
    public void deleteUser(Integer userId);

    /**
     * 根据id查询用户
     * @param userId
     * @return
     */
    @Select("select * from user where id = #{id}")
    public 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}")
    public List<User> findUserByName(String username);

    /**
     * 查询总用户数量
     * @return
     */
    @Select("select count(*) from user")
    public int findTotalUser();
}
  • 测试
package com.siyi.test;

import com.siyi.dao.IUserDao;
import com.siyi.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.Date;
import java.util.List;

public class AnnotationCRUD {
    private InputStream in;
    private SqlSessionFactory factory;
    private SqlSession session;
    private IUserDao iUserDao;

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

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

    @Test
    public void testSave(){
        User user = new User();
        user.setUsername("mybatis Annotation");
        user.setAddress("北京市昌平区");

        iUserDao.saveUser(user);
    }

    @Test
    public void testUpdateUser(){
        User user = new User();
        user.setId(57);
        user.setSex("男");
        user.setAddress("北京市海淀区");
        user.setUsername("mybatis annotation update");
        user.setBirthday(new Date());

        iUserDao.updateUser(user);
    }

    @Test
    public void testDeleteUser(){
        iUserDao.deleteUser(58);
    }

    @Test
    public void testFindOne(){
        User user = iUserDao.findById(57);
        System.out.println(user);
    }

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

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

3. 使用注解实现一对多复杂关系映射

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， 在使用注解开发时我们需要借助@Results 注解， @Result 注解， @One 注解， @Many 注解等等。

3.1 复杂关系映射的注解说明

@Results 注解
代替的是标签<resultMap>
该注解中可以使用单个@Result 注解，也可以使用@Result 集合
@Results({@Result()， @Result() })或@Results(@Result())

@Resutl 注解
代替了 <id>标签和<result>标签
@Result 中 属性介绍：
	id 是否是主键字段
	column 数据库的列名
	property 需要装配的属性名
	one 需要使用的@One 注解(@Result(one=@One())))
	many 需要使用的@Many 注解(@Result(many=@many())))
@One 注解（一对一）
	代替了<assocation>标签，是多表查询的关键，在注解中用来指定子查询返回单一对象。
@One 注解属性介绍：
	select 指定用来多表查询的 sqlmapper
	fetchType 会覆盖全局的配置参数 lazyLoadingEnabled。。
	使用格式：
		@Result(column=" ",property="",one=@One(select=""))
@Many 注解（多对一）
	代替了<Collection>标签,是是多表查询的关键，在注解中用来指定子查询返回对象集合。
	注意：聚集元素用来处理“一对多”的关系。需要指定映射的 Java 实体类的属性，属性的 javaType
	（一般为 ArrayList）但是注解中可以不定义；
	使用格式：
		@Result(property="",column="",many=@Many(select=""))

3.2 使用注解实现一对一复杂关系映射及延迟加载

  • 实体类（Account）
package com.siyi.domain;

public class Account {

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

    //多对一（mybatis中称之为1对1）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 +
                '}';
    }
}
  • 持久层接口
package com.siyi.dao;

import com.siyi.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,property = "id",column = "id"),
            @Result(property = "uid",column = "uid"),
            @Result(property = "money",column = "money"),
            @Result(property = "user",column = "uid",one = @One(
                    select = "com.siyi.dao.IUserDao.findById",
                    fetchType = FetchType.EAGER
            ))
    })
    public List<Account> findAll();

    /**
     * 根据用户id查询账户信息
     * @param userId
     * @return
     */
    @Select("select * from account where uid = #{userId}")
    public List<Account> findAccountByUid(Integer userId);
}
  • 测试类
package com.siyi.test;

import com.siyi.dao.IAccountDao;
import com.siyi.domain.Account;
import com.siyi.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 AccountTest {
    private InputStream in;
    private SqlSessionFactory factory;
    private SqlSession session;
    private IAccountDao iAccountDao;

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

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

    @Test
    public void testFindAll(){
        List<Account> accounts = iAccountDao.findAll();
        for(Account account : accounts){
            System.out.println("------------------");
            System.out.println(account);
            System.out.println(account.getUser());
        }
    }
}

3.3 使用注解实现一对多复杂关系映射及延迟加载

  • 实体类（User）
package com.siyi.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;

    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;
    }
}
  • 持久层接口
package com.siyi.dao;

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

import java.util.List;

/**
 * 在mybatis中针对，CRUD一共有四个注解
 * @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,property = "userId",column = "id"),
            @Result(property = "userName",column = "username"),
            @Result(property = "userAddress",column = "address"),
            @Result(property = "userSex",column = "sex"),
            @Result(property = "userBirthday",column = "birthday"),
            @Result(property = "accounts" , column = "id", many = @Many(
                    select = "com.siyi.dao.IAccountDao.findAccountByUid",
                    fetchType = FetchType.LAZY
            ))
    })
    /*@Many:
	相当于<collection>的配置
	select 属性：代表将要执行的 sql 语句
	fetchType 属性：代表加载方式，一般如果要延迟加载都设置为 LAZY 的值*/
    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")
    public 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}")
    @ResultMap("userMap")
//    @Select("select * from user where username like '%${value}%'")
    public List<User> findUserByName(String username);
}
  • 测试类
package com.siyi.test;

import com.siyi.dao.IUserDao;
import com.siyi.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.Date;
import java.util.List;

public class AnnotationCRUD {
    private InputStream in;
    private SqlSessionFactory factory;
    private SqlSession session;
    private IUserDao iUserDao;

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

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

    @Test
    public void testFindAll(){
        List<User> users = iUserDao.findAll();
        for(User user : users){
            System.out.println("---------------");
            System.out.println(user);
            System.out.println(user.getAccounts());
        }
    }

    @Test
    public void testFindOne(){
        User user = iUserDao.findById(57);
        System.out.println(user);
        User user1 = iUserDao.findById(57);
        System.out.println(user1);
        System.out.println(user==user1);
    }

    @Test
    public void testFindUserByName(){
        List<User> users = iUserDao.findUserByName("%私忆%");
//        List<User> users = iUserDao.findUserByName("私忆");
        for (User user : users){
            System.out.println(user);
        }
    }
}

4. 基于注解的二级缓存

  • 在 主配置文件SqlMapConfig.xml中开启二级缓存支持
<?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"/>
    
    <!-- 配置二级缓存 -->
    <settings>
        <setting name="cacheEnabled" value="true"/>
    </settings>
    
    <!-- 配置别名 -->
    <typeAliases>
        <package name="com.siyi.domain"/>
    </typeAliases>
    <!-- 配置环境 -->
    <environments default="mysql">
        <environment id="mysql">
            <transactionManager type="JDBC"></transactionManager>
            <dataSource type="POOLED">
                <property name="driver" value="${jdbc.driver}"/>
                <property name="url" value="${jdbc.url}"/>
                <property name="username" value="${jdbc.username}"/>
                <property name="password" value="${jdbc.password}"/>
            </dataSource>
        </environment>
    </environments>
    <!-- 引入带有注解的DAO接口所在位置 -->
    <mappers>
        <package name="com.siyi.dao"/>
    </mappers>
</configuration>
  • 在持久层接口中使用注解配置二级缓存
package com.siyi.dao;

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

import java.util.List;

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