mybatis(1)

1、MyBatis簡介

MyBatis 是支持普通 SQL 查詢，存儲過程和高級映射的優秀持久層框架。MyBatis 消除了幾乎全部的 JDBC 代碼和參數的手工設置以及結果集的檢索。MyBatis 使用簡單的 XML 或註解用於配置和原始映射，將接口和 Java 的 POJOs（Plan Old Java Objects，普通的 Java 對象）映射成數據庫中的記錄。

orm工具的基本思想

不管是用過的 hibernate,Mybatis,你均可以法相他們有一個共同點：

1. 從配置文件(一般是 XML 配置文件中)獲得 sessionfactory.
2. 由 sessionfactory 產生 session
3. 在 session 中完成對數據的增刪改查和事務提交等.
4. 在用完以後關閉 session 。
5. 在 Java 對象和 數據庫之間有作 mapping 的配置文件，也一般是 xml 文件。

2、HelloWorld

建立用戶表：

Create TABLE `user` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `userName` varchar(50) DEFAULT NULL,
  `userAge` int(11) DEFAULT NULL,
  `userAddress` varchar(200) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;

Insert INTO `user` VALUES ('1', 'summer', '100', 'shanghai,pudong');

結構圖以下：

Configuration.xml: 這裏使用mariadb做爲開發環境

<?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>
    <typeAliases>
        <typeAlias alias="User" type="demo.mybatis.helloworld.model.User"/>
    </typeAliases>

    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="org.mariadb.jdbc.Driver"/>
                <property name="url" value="jdbc:mariadb://192.168.1.202:3306/demo" />
                <property name="username" value="root"/>
                <property name="password" value="111111"/>
            </dataSource>
        </environment>
    </environments>

    <mappers>
        <mapper resource="mapper/User.xml"/>
    </mappers>
</configuration>

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>demo</groupId>
    <artifactId>mybatis</artifactId>
    <version>1.0-SNAPSHOT</version>
    <dependencies>
        <!-- https://mvnrepository.com/artifact/org.mybatis/mybatis -->
        <dependency>
            <groupId>org.mybatis</groupId>
            <artifactId>mybatis</artifactId>
            <version>3.2.8</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/org.mariadb.jdbc/mariadb-java-client -->
        <dependency>
            <groupId>org.mariadb.jdbc</groupId>
            <artifactId>mariadb-java-client</artifactId>
            <version>1.4.6</version>
        </dependency>

    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.1</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
                </configuration>
            </plugin>
        </plugins>
    </build>
</project>

User.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="demo.mybatis.helloworld.mapper.UserMapper">
    <select id="selectUserByID" parameterType="int" resultType="User">
        select * from `user` where id = #{id}
    </select>
</mapper>

User.java：

public class User {
    private int id;
    private String userName;
    private Integer userAge;
    private String userAddress;
    //get and set...
}

UserMapper:

public interface UserMapper {
    User selectUserByID(int id);
}

Test.java:

import java.io.Reader;

import demo.mybatis.helloworld.mapper.UserMapper;
import demo.mybatis.helloworld.model.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;

/**
 * Created by carl.yu on 2016/12/8.
 */
public class Test {
    private static SqlSessionFactory sqlSessionFactory;
    private static Reader reader;

    static {
        try {
            reader = Resources.getResourceAsReader("Configuration.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(reader);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static SqlSessionFactory getSession() {
        return sqlSessionFactory;
    }

    public static void main(String[] args) {
        SqlSession session = sqlSessionFactory.openSession();
        try {
            UserMapper userOperation=session.getMapper(UserMapper.class);
            User user = userOperation.selectUserByID(1);
            System.out.println(user.getUserAddress());
            System.out.println(user.getUserName());
        } finally {
            session.close();
        }
    }
}

3、CRUD

這裏直接用接口的方式編程。這種方式，要注意的一個地方就是。在 User.xml 的配置文件中，mapper namespace="demo.mybatis.helloworld.mapper.UserMapper" ，命名空間很是重要，不能有錯，必須與咱們定義的 package 和 接口一致。若是不一致就會出錯,這一章主要在上一講基於接口編程的基礎上完成以下事情:

1. 用 mybatis 查詢數據，包括列表
2. 用 mybatis 增長數據
3. 用 mybatis 更新數據
4. 用 mybatis 刪除數據

1. 查詢數據，前面已經講過簡單的，主要看查詢出列表的

查詢出列表，也就是返回 list, 在咱們這個例子中也就是 List , 這種方式返回數據，須要在 User.xml 裏面配置返回的類型 resultMap, 注意不是 resultType, 而這個 resultMap 所對應的應該是咱們本身配置的

<!-- 爲了返回list 類型而定義的returnMap -->
    <resultMap type="User" id="resultListUser">
        <id column="id" property="id" />
        <result column="userName" property="userName" />
        <result column="userAge" property="userAge" />
        <result column="userAddress" property="userAddress" />
    </resultMap>

查詢列表的語句在 User.xml 中

<!-- 返回list 的select 語句，注意 resultMap 的值是指向前面定義好的 -->
    <select id="selectUsers" parameterType="string" resultMap="resultListUser">
        select * from user where userName like #{userName}
    </select>

在 UserMapper接口中增長方法：public List selectUsers(String userName);

如今在 Test 類中作測試

public void getUserList(String userName){
        SqlSession session = sqlSessionFactory.openSession();
        try {
            UserMapper userOperation=session.getMapper(UserMapper.class);           
            List<User> users = userOperation.selectUsers(userName);
            for(User user:users){
                System.out.println(user.getId()+":"+user.getUserName()+":"+user.getUserAddress());
            }

        } finally {
            session.close();
        }
    }

如今在 main 方法中能夠測試：

public static void main(String[] args) {
        Test testUser=new Test();
        testUser.getUserList("%");
    }

 

能夠看到，結果成功查詢出來。若是是查詢單個數據的話，用第二講用過的方法就能夠了。

2. 用 mybatis 增長數據

在 UseMapper接口中增長方法：

public void addUser(User user);

在 User.xml 中配置

<!--執行增長操做的SQL語句。id和parameterType  
       分別與UserMapper接口中的addUser方法的名字和  
       參數類型一致。以#{name}的形式引用Student參數  
       的name屬性，MyBatis將使用反射讀取Student參數  
       的此屬性。#{name}中name大小寫敏感。引用其餘  
       的gender等屬性與此一致。seGeneratedKeys設置  
       爲"true"代表要MyBatis獲取由數據庫自動生成的主  
       鍵；keyProperty="id"指定把獲取到的主鍵值注入  
       到Student的id屬性--> 
    <insert id="addUser" parameterType="User" 
        useGeneratedKeys="true" keyProperty="id"> 
        insert into user(userName,userAge,userAddress)  
             values(#{userName},#{userAge},#{userAddress})  
    </insert>

而後在 Test 中寫測試方法:

/**
     * 測試增長,增長後，必須提交事務，不然不會寫入到數據庫.
     */
    public void addUser(){
        User user=new User();
        user.setUserAddress("人民廣場");
        user.setUserName("飛鳥");
        user.setUserAge(80);
        SqlSession session = sqlSessionFactory.openSession();
        try {
            UserMapper userOperation=session.getMapper(UserMapper.class);
            userOperation.addUser(user);
            session.commit();
            System.out.println("當前增長的用戶 id爲:"+user.getId());
        } finally {
            session.close();
        }
    }

3. 用 mybatis 更新數據

方法相似，先在 UserMapper中增長方法：

public void updateUser(User user);

而後配置 User.xml

<update id="updateUser" parameterType="User" >
        update user set userName=#{userName},userAge=#{userAge},userAddress=#{userAddress} where id=#{id}
   </update>

Test 類總的測試方法以下：

public void updateUser(){
        //先獲得用戶,而後修改，提交。
        SqlSession session = sqlSessionFactory.openSession();
        try {
            UserMapper userOperation=session.getMapper(UserMapper.class);
            User user = userOperation.selectUserByID(4);            
            user.setUserAddress("原來是魔都的浦東創新園區");
            userOperation.updateUser(user);
            session.commit();

        } finally {
            session.close();
        }
    }

4. 用 mybatis 刪除數據

同理，UserMapper增長方法：public void deleteUser(int id);

配置 User.xml

<delete id="deleteUser" parameterType="int">
        delete from user where id=#{id}
    </delete>

而後在 Test 類中寫測試方法:

 /**
     * 刪除數據，刪除必定要 commit.
     * @param id
     */
    public void deleteUser(int id){
        SqlSession session = sqlSessionFactory.openSession();
        try {
            IUserOperation userOperation=session.getMapper(IUserOperation.class);           
            userOperation.deleteUser(id);
            session.commit();            
        } finally {
            session.close();
        }
    }

這樣，全部增刪改查都完成了，注意在增長，更改，刪除的時候要調用 session.commit()，這樣纔會真正對數據庫進行操做，不然是沒有提交的。

到此爲止，簡單的單表操做，應該都會了，接下來的時間了，我會講多表聯合查詢，以及結果集的選取。

4、spring boot 配置mybatis

參考文章：http://www.mybatis.org/spring-boot-starter/mybatis-spring-boot-autoconfigure/

MyBatis-Spring-Boot-Starter will:

• 自動探測 DataSource.
• 自動根據探測到的DataSource建立SqlSessionFactoryBean .
• Will create and register an instance of a SqlSessionTemplate got out of the SqlSessionFactoryBean.
• Autoscan your mappers, link them to the SqlSessionTemplate and register them to Spring context so they can be injected into your beans.

能夠配置的信息有：

Property	Description
config-location	MyBatis xml config file (optional)
mapper-locations	Mapper xml config files (optional)
type-aliases-package	Package to search for type aliases (optional)
type-handlers-package	Package to search for type aliases (optional)
executor-type	Executor type: SIMPLE, REUSE, BATCH (optional)

文件圖：

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>demo</groupId>
    <artifactId>demo.mybatis</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <name>demo</name>
    <description>mybatis spring boot demo</description>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>1.4.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.mybatis.spring.boot</groupId>
            <artifactId>mybatis-spring-boot-starter</artifactId>
            <version>1.1.1</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <!-- https://mvnrepository.com/artifact/com.alibaba/druid -->
        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>druid</artifactId>
            <version>1.0.18</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.mariadb.jdbc/mariadb-java-client -->
        <dependency>
            <groupId>org.mariadb.jdbc</groupId>
            <artifactId>mariadb-java-client</artifactId>
            <version>1.4.6</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

application.properties：

jdbc.driverClassName=org.mariadb.jdbc.Driver
jdbc.url=jdbc:mariadb://192.168.1.202:3306/demo
jdbc.username=root
jdbc.password=111111

mybatis.config-location=classpath:mybatis-config.xml

logging.level.root=WARN
logging.level.sample.mybatis.mapper=TRACE

mybatis-config.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>
    <typeAliases>
        <!--<package name="sample.mybatis.domain"/>-->
        <typeAlias alias="User" type="demo.domain.User"/>
    </typeAliases>
    <mappers>
        <mapper resource="mapper/User.xml"/>
    </mappers>
</configuration>

MyBatisConfig: 配置數據源

package demo;

import com.alibaba.druid.pool.DruidDataSourceFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;

import javax.sql.DataSource;
import java.util.Properties;

/**
 * Created by carl.yu on 2016/12/8.
 */
@Configuration
public class MyBatisConfig {
    @Autowired
    private Environment env;

    /**
     * 建立數據源
     *
     * @Primary 該註解表示在同一個接口有多個實現類能夠注入的時候，默認選擇哪個，而不是讓@autowire註解報錯
     */
    @Bean
    //@Primary
    public DataSource getDataSource() throws Exception {
        Properties props = new Properties();
        props.put("driverClassName", env.getProperty("jdbc.driverClassName"));
        props.put("url", env.getProperty("jdbc.url"));
        props.put("username", env.getProperty("jdbc.username"));
        props.put("password", env.getProperty("jdbc.password"));
        props.put("testWhileIdle", "false");
        return DruidDataSourceFactory.createDataSource(props);
    }
}

配置User.xml:

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"
        "http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="demo.dao.UserMapper">
    <select id="selectUserByID" parameterType="int" resultType="User">
        select * from `user` where id = #{id}
    </select>

    <resultMap type="User" id="resultListUser">
        <id column="id" property="id"/>
        <result column="userName" property="userName"/>
        <result column="userAge" property="userAge"/>
        <result column="userAddress" property="userAddress"/>
    </resultMap>

    <!-- 返回list 的select 語句，注意 resultMap 的值是指向前面定義好的 -->
    <select id="selectUsers" parameterType="string" resultMap="resultListUser">
        select * from user where userName like #{userName}
    </select>
    <!--執行增長操做的SQL語句。id和parameterType
       分別與UserMapper接口中的addUser方法的名字和
       參數類型一致。以#{name}的形式引用Student參數
       的name屬性，MyBatis將使用反射讀取Student參數
       的此屬性。#{name}中name大小寫敏感。引用其餘
       的gender等屬性與此一致。seGeneratedKeys設置
       爲"true"代表要MyBatis獲取由數據庫自動生成的主
       鍵；keyProperty="id"指定把獲取到的主鍵值注入
       到Student的id屬性-->
    <insert id="addUser" parameterType="User"
            useGeneratedKeys="true" keyProperty="id">
        insert into user(userName,userAge,userAddress)
        values(#{userName},#{userAge},#{userAddress})
    </insert>

    <update id="updateUser" parameterType="User">
        update user set userName=#{userName},userAge=#{userAge},userAddress=#{userAddress} where id=#{id}
    </update>

    <delete id="deleteUser" parameterType="int">
        delete from user where id=#{id}
    </delete>
</mapper>

配置UserMapper：

package demo.dao;


import demo.domain.User;
import org.apache.ibatis.annotations.Mapper;

import java.util.List;

/**
 * Created by carl.yu on 2016/12/8.
 */
@Mapper
public interface UserMapper {
    User selectUserByID(int id);

    public List selectUsers(String userName);

    public void addUser(User user);

    public void updateUser(User user);
}

能夠直接使用了: UserService

package demo.service;

import demo.dao.UserMapper;
import demo.domain.User;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.List;

/**
 * Created by carl.yu on 2016/12/8.
 */
@Service
public class UserService {
    @Autowired
    private UserMapper userMapper;

    @Transactional(readOnly = true)
    public List<User> findAll() {
        return userMapper.selectUsers("%");
    }
}