1. 程式人生 > 實用技巧 >Mybatis建立連線

Mybatis建立連線

maven 倉庫:

<dependency>
<groupId>mysql</groupId>
<artifactId>mysql-connector-java</artifactId>
<version>5.1.46</version>
</dependency>

<dependency>
<groupId>org.mybatis</groupId>
<artifactId>mybatis</artifactId>
<version>3.5.2</version>
</dependency>

<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.12</version>
<scope>test</scope>
</dependency>

1.首先編寫 Mabatis工具類:

package com.wang.utils;

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;

public class MybatisUtils {
private static SqlSessionFactory sqlSessionFactory;
static {
try {
String resource="mybatis-config.xml";
InputStream is = Resources.getResourceAsStream(resource);

System.out.println(is);
sqlSessionFactory=new SqlSessionFactoryBuilder().build(is);
} catch (Exception e) {
e.printStackTrace();
}
}
public static SqlSession getSqlSession(){
return sqlSessionFactory.openSession();
}
}
在其中準備連線資料庫所需資源(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>
<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/wang?useUnicode=true&amp;characterEncoding=UTF-8" />
<property name="username" value="root" />
<property name="password" value="123456" />
</dataSource>
</environment>
</environments>
<mappers>
<mapper resource="com/wang/dao/UserMapp.xml"></mapper>
</mappers>
</configuration>

注:在mybatis-config.xml檔案中 需要與第二步中的Mapp建立聯絡,格式如下:
    <mappers>
<mapper resource="com/wang/dao/UserMapp.xml"></mapper>
</mappers>


2.編寫Dao中檔案:(Dao介面,Mapp.xml)
Dao介面檔案:可以在已新增介面
package com.wang.dao;

import com.wang.Pojo.User;
import java.util.List;
public interface UserDao {
List<User> getUser();
}
Mapp.xml檔案:
<?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="com.wang.dao.UserDao">
<select id="getUser" resultType="com.wang.Pojo.User">
SELECT * FROM user
</select>
</mapper>

注:其中nameSpace是Dao介面的檔案
id為Dao介面中的方法
resultType為返回結果的型別


3.編寫主程式:

//第一步,用工具類獲取sqlSession。
SqlSession sqlSession = MybatisUtils.getSqlSession();
//第二步,獲取Dao物件
UserDao userDao = sqlSession.getMapper(UserDao.class);
//第三步,通過Dao物件呼叫其中的方法,返回集合
List<User> list = userDao.getUser();
for(User u:list){
System.out.println(u.toString());//遍歷結果集
}

sqlSession.close();//關閉資源

宣告:(Mapp.xml匯出資源問題):需要在pom.xml檔案新增以下程式碼:
<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>