第一個Mybatis
阿新 • • 發佈:2020-08-09
第一個Mybatis
思路:搭建環境-->匯入Mybatis-->編寫程式碼-->測試
1、搭建環境
新建maven工程,配置xml檔案
<?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>org.example</groupId> <artifactId>mybatis</artifactId> <version>1.0-SNAPSHOT</version> <!--匯入依賴--> <dependencies> <!--mysql驅動--> <dependency> <groupId>mysql</groupId> <artifactId>mysql-connector-java</artifactId> <version>5.1.47</version> </dependency> <!--mybatis--> <dependency> <groupId>org.mybatis</groupId> <artifactId>mybatis</artifactId> <version>3.5.2</version> </dependency> <!--junit--> <dependency> <groupId>junit</groupId> <artifactId>junit</artifactId> <version>4.12</version> <scope>test</scope> </dependency> </dependencies> </project>
- 編寫mybatis的核心配置檔案(在resources資料夾下建立mybatis-config.xml)
Mysql8.0以上url還得設定時區setTimeZone
<?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核心配置檔案--> <configuration> <environments default="development"> <environment id="development"> <transactionManager type="JDBC"/> <!--資料來源--> <dataSource type="POOLED"> <property name="driver" value="com.mysql.jdbc.Driver"/> <property name="url" value="jdbc:mysql://localhost:3306/mybatis?useSSL=true&useUnicode=true&characterEncode=UTF-8"/> <property name="username" value="root"/> <property name="password" value="123456"/> </dataSource> </environment> </environments> <!--每一個Mapper.xml都需要在mybatis核心配置檔案中註冊!--> <mappers> <mapper resource="org/mybatis/example/UserDaoMapper.xml"/> </mappers> </configuration>
2、編寫程式碼
-
實體類
package com.spong.pojo; public class User { private int id; private String name; private String pwd; public User() { } public User(int id, String name, String pwd) { this.id = id; this.name = name; this.pwd = pwd; } public int getId() { return id; } public void setId(int id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getPwd() { return pwd; } public void setPwd(String pwd) { this.pwd = pwd; } @Override public String toString() { return "User{" + "id=" + id + ", name='" + name + '\'' + ", pwd='" + pwd + '\'' + '}'; } }
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Mapper介面
public interface UserMapper { List<User> getUserList(); }
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介面實現類由原來的UserDaoImpl轉變為一個Mapper配置檔案 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"> <!--namespace繫結一個對應的Dao/Mapper介面--> <mapper namespace="com.spong.dao.UserDao"> <select id="getUserList" resultType="com.spong.pojo.User"> select * from mybatis.user </select> </mapper>
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MybatisUtils工具類
將sqlSessionFactory的建立以及獲取SqlSession的方法封裝為工具類,實際請求中使用MybatisUtils工具類的靜態方法直接獲得SQLSession例項。
package com.spong.util; 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.IOException; import java.io.InputStream; public class MybatisUtils { private static SqlSessionFactory sqlSessionFactory; static { try { //獲取SqlSessionFactory物件 String resource = "mybatis-config.xml"; InputStream inputStream = Resources.getResourceAsStream(resource); sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream); } catch (IOException e) { e.printStackTrace(); } } //獲取SQLSession例項,SQLSession中完全包含了面向資料庫執行SQL命令所需的所有方法 public static SqlSession getSqlSession(){ return sqlSessionFactory.openSession(); } }
3、測試
junit測試
@Test
public void test(){
//第一步,獲取SqlSession物件
SqlSession sqlSession = MybatisUtils.getSqlSession();
//第二步,執行sql
UserMapper mapper = sqlSession.getMapper(UserMapper.class);
List<User> userList = mapper.getUserList();
for (User user : userList) {
System.out.println(user);
}
//關閉SqlSession
sqlSession.close();
}
異常:org.apache.ibatis.binding.BindingException: Type interface com.spong.dao.UserDao is not known to the MapperRegistry.
需要在核心配置檔案中註冊mappers
<!--每一個Mapper.xml檔案都要在核心配置檔案中註冊-->
<mappers>
<mapper resource="com/spong/dao/UserMapper.xml"/>
</mappers>
maven資源匯出問題(測試時發現mybatis.xml檔案未找到):
需要在pom.xml中配置
<!--在build中配置resources,防止資源匯出失敗的問題-->
<build>
<resources>
<resource>
<directory>src/main/resources</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
</resource>
<resource>
<directory>src/main/java</directory>
<includes>
<include>**/*.properties</include>
<include>**/*.xml</include>
</includes>
</resource>
</resources>
</build>