Mybatis—學習基礎
阿新 • • 發佈：2018-12-06
Mybatis基於java的持久層框架，內部封裝了JDBC，使開發只需要關注SQL語句。Mybatis通過xml或註解方式將要執行的各種statement配置，通過java物件和Statement中SQL的動態引數進行對映生成最終執行的SQL語句，最後由Mybatis框架執行SQL並將結果對映成Java物件並返回。
Mybatis工作原理圖：
簡單實現Mybatis
1、實體類
Student.java
public class Student {
private Integer id;
private String name;
private 2、sql檔案
SET FOREIGN_KEY_CHECKS=0;
-- ----------------------------
-- Table structure for student
-- ----------------------------
DROP TABLE IF EXISTS `student`;
CREATE TABLE `student` (
`id` int(5) NOT NULL AUTO_INCREMENT,
`name` varchar(20) DEFAULT NULL,
`age` int(3) DEFAULT NULL,
`score` double DEFAULT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=latin1;
-- ----------------------------
-- Records of student
-- ----------------------------
INSERT INTO `student` VALUES ('1', 'lov1', '20', '99.9');
INSERT INTO `student` VALUES ('2', 'lov2', '22', '69.5');
INSERT INTO `student` VALUES ('3', 'lov3', '21', '66');
-- ----------------------------
-- Table structure for user
-- ----------------------------
DROP TABLE IF EXISTS `user`;
CREATE TABLE `user` (
`userid` varchar(30) NOT NULL,
`name` varchar(30) NOT NULL,
`password` varchar(32) NOT NULL,
PRIMARY KEY (`userid`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
-- ----------------------------
-- Records of user
-- ----------------------------
INSERT INTO `user` VALUES ('admin', 'admin', 'admin');
3、配置檔案
mybatis.xml（根目錄下，規定命名；連線資料庫，載入其他相關配置檔案）
<?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>
<!-- 註冊db連線屬性檔案 -->
<properties resource="jdbc_mysql.properties" />
<!-- 定義類型別名 -->
<typeAliases>
<!-- <typeAlias type="com.lov.beans.Student" alias="Student"/> -->
<!-- 將指定包中的所有類的簡單類名當作其別名 -->
<package name="com.lov.beans"/>
</typeAliases>
<!-- 配置執行環境 -->
<environments default="mysqlEM">
<environment id="mysqlEM">
<transactionManager type="JDBC"></transactionManager>
<dataSource type="POOLED">
<property name="driver" value="${jdbc.driver}"/>
<!-- jdbc:mysql:///lov 預設的127.0.0.1可以省略-->
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</dataSource>
</environment>
</environments>
<!-- 註冊對映檔案mapper.xml -->
<mappers>
<mapper resource="com/lov/dao/mapper.xml"/>
</mappers>
</configuration>
mapper.xml（相應的bean目錄檔案下，需在mybatis.xml檔案中註冊）
<?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.lov.dao.IStudentDao">
<!--namespace作用：在有多個mapper.xml檔案，且檔案中有相同sql語句，可通過namespace區別，namespace不可重複-->
<!-- 這裡寫的是sql語句，這裡用簡單實現insert-->
<insert id="insertStudent" parameterType="Student">
<!-- id:在dao實現類中引用的sql語句名字；paramterType：可通過在mybatis.xml中定義的實體類別名，或相應類的全限定性類名-->
insert into student(name,age,score) value (#{name},#{age},#{score})
</insert>
</mapper>mysql.properties（連線四要素，需在mybatis.xml註冊）
jdbc.driver=com.mysql.jdbc.Driver
jdbc.url=jdbc:mysql://127.0.0.1:3306/lov
jdbc.username=root
jdbc.password=passwordlog4j.properties（用log4j輸出日誌）
### 輸出資訊到控制擡 ###
log4j.appender.console = org.apache.log4j.ConsoleAppender
log4j.appender.console.Target=System.out
log4j.appender.console.layout=org.apache.log4j.PatternLayout
log4j.appender.console.layout.ConversionPattern= %m%n
### 設定###
log4j.logger.com.lov.dao.IStudentDao = debug,console4、dao實現類
IStudentDao.java
import java.util.List;
import java.util.Map;
import com.lov.beans.Student;
public interface IStudentDao {
void insertStudent(Student student);
void insertStudentCacheId(Student student);
void deleteStudentById(int id);
void updateStudent(Student student);
List<Student> selectAllStudents();
Map<String,Object> selectAllStudentsMap();
Student selectStudentById(int id);
List<Student> selectStudentsByName(String name);
}
StudentDaoImpl.java
import org.apache.ibatis.session.SqlSession;
import com.lov.beans.Student;
import com.lov.utils.MyBatisUtils;
public class StudentDaoImpl implements IStudentDao {
private SqlSession sqlSession;
@Override
public void insertStudent(Student student) {
try {
//變成工具類中執行
/*InputStream inputStream;
//1、載入主配置檔案
inputStream = Resources.getResourceAsStream("mybatis.xml");
//2、建立SqlSessionFactory物件
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream );
//3、建立SqlSession物件
sqlSession = sqlSessionFactory.openSession();*/
sqlSession = MyBatisUtils.getSqlSession();
//4、相關操作
sqlSession.insert("insertStudent", student);//mapper.xml的sqlid
sqlSession.commit();//提交後自動進行事務回滾
}finally {
if(sqlSession != null){
sqlSession.close();//sqlSession實質是流的操作
}
}
}
@Override
public void insertStudentCacheId(Student student) {
}
@Override
public void deleteStudentById(int id) {
}
@Override
public void updateStudent(Student student) {
}
@Override
public List<Student> selectAllStudents() {
return null;
}
@Override
public Map<String, Object> selectAllStudentsMap() {
return null;
}
@Override
public Student selectStudentById(int id) {
return null;
}
@Override
public List<Student> selectStudentsByName(String name) {
return null;
}
}5、工具類
MybatisUtils.java
import java.io.IOException;
import java.io.InputStream;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
public class MyBatisUtils {
private static SqlSessionFactory sqlSessionFactory;
public static SqlSession getSqlSession(){
InputStream is;
try {
is = Resources.getResourceAsStream("mybatis.xml");
if(sqlSessionFactory == null){
sqlSessionFactory = new SqlSessionFactoryBuilder().build(is);
}
return sqlSessionFactory.openSession();
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
}
6、測試類
Mytest.java（Junit做測試）
import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import com.lov.beans.Student;
import com.lov.dao.IStudentDao;
import com.lov.dao.StudentDaoImpl;
public class MyTest {
private IStudentDao dao;
@Before
public void before(){
dao = new StudentDaoImpl();
}
@Test
public void testInsert(){
Student student = new Student("lov_1",22,98.5);
dao.insertStudent(student);
}
}