1. 程式人生 > 實用技巧 >第一個mybatis專案(查詢表User中所有資料)

第一個mybatis專案(查詢表User中所有資料)

1、在pom.xml中配置:

//依賴配置:
<dependencies>
    <dependency>
        <groupId>org.mybatis</groupId>
        <artifactId>mybatis</artifactId>
        <version>3.4.4</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId> <version>5.1.6</version> </dependency> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> </
dependency> </dependencies>

//防止資原始檔匯出失敗:
<build>
    <resources>
        <resource>
            <directory>src/main/resources</directory>
            <includes>
                <include>**/*.properties</include>
                <include>**/*.xml</
include> </includes> <filtering>true</filtering> </resource> <resource> <directory>src/main/java</directory> <includes> <include>**/*.properties</include> <include>**/*.xml</include> </includes> <filtering>true</filtering> </resource> </resources> </build>

2、建立mybatis-config.xml檔案,一般放入maven專案中的resource目錄中:
<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=GMT%2B8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
</configuration>

其中driver為jdbc驅動:com.mysql.jdbc.Driver,url為資料庫地址,username為使用者名稱,password為密碼。

2、編寫mybatis工具類mybatisUtils:
public class MybatisUtils {
    private static SqlSessionFactory sqlSessionFactory;
    static{
        try{
            String resource = "mybatis-config.xml";
            InputStream inputStream = Resources.getResourceAsStream(resource);
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    public static SqlSession getSqlSession(){
        return sqlSessionFactory.openSession();
    }
}
//以上內容基本上是寫死了的

3、建立一個javabean,欄位與表中的欄位一致。
public class User {
    private String username;
    private String pswd;
    private String sex;
    public User(){}

    public User(String username, String pswd, String sex) {
        this.username = username;
        this.pswd = pswd;
        this.sex = sex;
    }

    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public String getPswd() {
        return pswd;
    }

    public void setPswd(String pswd) {
        this.pswd = pswd;
    }

    public String getSex() {
        return sex;
    }

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

    @Override
    public String toString() {
        return "User{" +
                "username='" + username + '\'' +
                ", pswd='" + pswd + '\'' +
                ", sex='" + sex + '\'' +
                '}';
    }
}
4、編寫UserMapper介面:
public interface UserMapper {
    public List getUserList();
}

5、編寫UserMapper介面對應的xml:UserMapper.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="dao.UserMapper">
    <select id="getUserList" resultType="pojo.User">
        select * from mybatis.user
    </select>
</mapper>

注意:namespace繫結UserMapper介面,id與介面中的getUserList()方法關聯,resultType繫結剛才編寫的javabean:User
select標籤內容為sql查詢語句:select * from mybatis.user
6、去mybatis-config.xml中把剛才寫的UserMapper.xml註冊上:
<?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>
    <environments default="development">
        <environment id="development">
            <transactionManager type="JDBC"/>
            <dataSource type="POOLED">
                <property name="driver" value="com.mysql.jdbc.Driver"/>
                <property name="url" value="jdbc:mysql://localhost:3306?useSSL=true&amp;useUnicode=true&amp;characterEncoding=UTF-8&amp;serverTimezone=GMT%2B8"/>
                <property name="username" value="root"/>
                <property name="password" value="root"/>
            </dataSource>
        </environment>
    </environments>
    <mappers>
        <mapper resource="./dao/UserMapper.xml" />
    </mappers>
</configuration>

可以發現就是使用了mappers,mapper標籤:
<mappers>
    <mapper resource="./dao/UserMapper.xml" />
</mappers>

7、編寫測試類進行驗證:

我這裡使用junit:
@Test
public void test(){
    SqlSession sqlSession = new MybatisUtils().getSqlSession();
    UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
    List<User> userList = userMapper.getUserList();
    for(User user:userList){
        System.out.println(user);
    }
    sqlSession.close();
}

結果:

8、最後附上一張專案結構圖以作參考: