Java第三十七天，Mybatis框架系列，基于多表操作的注解开发

一、常用注解

• @Results ===> 解决实体类和数据库表属性名称不一致问题；其中可以包含任意 @Result ；功能类似于 <resultMap>
• @Result ===> 作为 @Results 的子元素，配合 @Result 使用
• @ResultMap ===> 其他地方调用 @Results 注解时使用；配合 @Result 使用

1.@Result

（1）功能相当于以下两标签

<id>
<result>

（2）属性

属性及其意义

id ===> 标识是否是主键
column ===> 对应的数据库的列名
property ===> 对应的实体类的属性名
one ===> 需要使用的 @One 注解   (@Result(one=@One)()))
many ===> 需要使用的 @Many 注解   (@Result(many=@many)()))


=============================================================================


当启用 one（一对一） | many（多对多） 属性时；可利用 fetchType 属性设置数据库数据加载方式

LAZY ===> 延迟加载
EAGER ===> 立即加载
DEFAULT ===> 默认取值；一对一：立即，多对多：延迟）

例如：
@Result(property = "对应的实体类属性名",column = "对应的数据库表字段名",one = @One(select="功能接口方法",fetchType= 加载方式))

@Result(property = "对应的实体类属性名",column = "对应的数据库表字段名",many = @Many(select="功能接口方法",fetchType= 加载方式))

（3）举例

// 主键；数据库表中字段名为 id， 对应着实体类中的 userId 属性

@Result(id=true,column = "id",property = "userId")

2.@Results

（1）功能类似于以下标签

<resultMap>

（2）使用方法

@Results(id="唯一标识符",value={
            @Result(id=?,column=?,property=?),
            @Result(column = "username",property = "userName"),
            ......
            // 该注解中可以使用单个@Result 注解，也可以使用@Result 集合
})

3.@ResultMap

（1）使用方法

@ResultMap(value="已经定义好的 @Results 数组")
或
@ResultMap(value="已经定义好的 @Results")


@ResultMap("已经定义好的 @Results 数组")
或
@ResultMap("已经定义好的 @Results")

二、项目实战

1.用户实体类

package com.lanyue.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 +
                '}';
    }
}

2.账号实体类

package com.lanyue.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 +
                '}';
    }
}

3.用户功能接口

package com.lanyue.dao;

import com.lanyue.domain.User;
import org.apache.ibatis.annotations.*;
import org.apache.ibatis.mapping.FetchType;
import java.util.List;

@CacheNamespace(blocking = true)
public interface IUserDao {

    //查询所有用户
    // @Result 注解包含 column 和 property 以及 id 三个属性
    // id 用来标识该建是否为主键
    // column 用来标识 数据库 中的字段名称；property 用来标识实体类中的属性名称
    // @Results 注解功能类似标签<resultMap>；该注解中可以使用单个@Result 注解，也可以使用@Result 集合
    // @Results 中的 id 可以作为该 map 的唯一标识，方便以后多次调用使用；使用时通过 @ResultMap 注解指定
    @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"),

            // select 用于指定得到该属性值的方法（功能接口中的方法） ===> 全限定类名 + 方法名
            @Result(property = "accounts",column = "id",
                    many = @Many(select = "com.lanyue.dao.IAccountDao.findAccountByUid",
                                fetchType = FetchType.LAZY))
    })
    List<User> findAll();

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

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

4.账号功能接口

package com.lanyue.dao;

import com.lanyue.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
    @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"),

            // select 用于指定得到该属性值的方法（功能接口中的方法） ===> 全限定类名 + 方法名
            // fetchType 用于指明数据库信息加载方式；共有如下几种
            /**
             * LAZY ===> 延迟加载
             * EAGER ===> 立即加载
             * DEFAULT ===> 默认取值；一对一：立即，多对多：延迟）
             */
            @Result(property = "user",column = "uid",one=@One(select="com.lanyue.dao.IUserDao.findById",fetchType= FetchType.EAGER))
    })
    List<Account> findAll();

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

5.测试类

package com.lanyue.test;

import com.lanyue.dao.IAccountDao;
import com.lanyue.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;

/**
 * @author 黑马程序员
 * @Company 
 */
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());
        }
    }



}

6.数据库连接文件——jdbc.properties

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

7.mybatis 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"></properties>
    <!--配置开启二级缓存-->
    <settings>
        <setting name="cacheEnabled" value="true"/>
    </settings>

    <!--配置别名-->
    <typeAliases>
        <package name="com.lanyue.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>
       <package name="com.lanyue.dao"></package>
    </mappers>
</configuration>

8.日志配置文件——log4j.properties

# Set root category priority to INFO and its only appender to CONSOLE.
#log4j.rootCategory=INFO, CONSOLE            debug   info   warn error fatal
log4j.rootCategory=debug, CONSOLE, LOGFILE

# Set the enterprise logger category to FATAL and its only appender to CONSOLE.
log4j.logger.org.apache.axis.enterprise=FATAL, CONSOLE

# CONSOLE is set to be a ConsoleAppender using a PatternLayout.
log4j.appender.CONSOLE=org.apache.log4j.ConsoleAppender
log4j.appender.CONSOLE.layout=org.apache.log4j.PatternLayout
log4j.appender.CONSOLE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

# LOGFILE is set to be a File appender using a PatternLayout.
log4j.appender.LOGFILE=org.apache.log4j.FileAppender
log4j.appender.LOGFILE.File=d:\axis.log
log4j.appender.LOGFILE.Append=true
log4j.appender.LOGFILE.layout=org.apache.log4j.PatternLayout
log4j.appender.LOGFILE.layout.ConversionPattern=%d{ISO8601} %-6r [%15.15t] %-5p %30.30c %x - %m\n

9.Maven 配置文件——pom.xml

<?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_04annoOne2Many</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>