Mybatis 学习笔记（一）—— 基础方式的CRUD
Mybatis
Mybatis（前身ibatis，2010被Google收购后改名为mybatis）是一个支持普通SQL查询、存储过程以及高级映射的持久层框架。Mybatis是一种ORM（Object/Relational Mapping）框架，它通过描述Java对象与数据库表之间的映射关系，自动将Java应用程序中的对象持久化到关系型数据库表中。
入门示例
Mybatis配置文件config.xml
<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/goodsadmin"/>
<property name="username" value="root"/>
<property name="password" value="120329"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="com/johnny/entity/personMapper.xml"/>
mappers>
configuration>
personMapper.xml
<mapper namespace="com.johnny.personMapper">
<select id="selectPersonById" resultType="com.johnny.entity.Person">
select * from person where id = #{id}
select>
mapper>
实体类Person.java,其属性与数据库中的表person 的字段相对应
package com.johnny.entity;
public class Person {
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return this.id+","+ this.name+", " +this.age;
}
private int id;
private String name;
private int age;
}
person表
测试类
package com.johnny.entity;
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 TestMybatis {
public static void main(String[] args) throws IOException {
//1、加载资源文件：获取mybatis配置文件输入流/MybatisDemo0/src/com/johnny/entity/config.xml
InputStream in = Resources.getResourceAsStream("config.xml");
//2、 通过 SqlSessionFactoryBuilder 获得SqlSessionFactory 的实例
SqlSessionFactory sqlFactory = new SqlSessionFactoryBuilder().build(in);
//3、获取session对象 --相当于JDBC中的Connection对象
SqlSession session = sqlFactory.openSession();
//xml命名空间+sql语句id
String statement = "com.johnny.personMapper.selectPersonById";
Person per = session.selectOne(statement,1);
System.out.println(per);
}
}
- 配置mybatis配置文件config.xml,改文件中配置数据库信息和需要加载的映射文件
- 将表和实体通过xxxMapper.xml 关联其阿里
- 测试类通过sqlsessionFactory获取session对象。
使用mybatis实现增删改查
- 输入参数parameterType和输出参数resultType 在形式上只能有一个
- 如果输入参数是简单类型（8个基本数据类型 + String），则可以使用任意占位符 #{xx}。但是如果是对象类型则必须是对象的属性 #{属性名}
- 返回类型。不论返回值是一个还是多个，resultType只需指定元素的类型即可，不用集合。
personManager.xml
<mapper namespace="com.johnny.personMapper">
<select id="selectPersonById" resultType="com.johnny.entity.Person">
select * from person where id = #{id}
select>
<select id="selectAllPerson" resultType="com.johnny.entity.Person">
select * from person
select>
<insert id="addPerson" parameterType="com.johnny.entity.Person">
insert into person(id, age, name) values( #{id}, #{age}, #{name})
insert>
update person set name = #{name}, age =#{age} where id = #{id}
update>
delete from person where id=#{id}
delete>
mapper>
配置文件config.xml
<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/goodsadmin"/>
<property name="username" value="用户名"/>
<property name="password" value="密码"/>
dataSource>
environment>
environments>
<mappers>
<mapper resource="com/johnny/entity/personMapper.xml"/>
mappers>
configuration>
测试类：TestMybatis
package com.johnny.entity;
import java.io.IOException;
import java.io.InputStream;
import java.util.List;
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 TestMybatis {
public static void selectPersonById() throws IOException {
//1、加载资源文件：获取mybatis配置文件输入流/MybatisDemo0/src/com/johnny/entity/config.xml
InputStream in = Resources.getResourceAsStream("config.xml");
//2、 通过 SqlSessionFactoryBuilder 获得SqlSessionFactory 的实例
SqlSessionFactory sqlFactory = new SqlSessionFactoryBuilder().build(in);
//3、获取session对象 --相当于JDBC中的Connection对象
SqlSession session = sqlFactory.openSession();
//xml命名空间+sql语句id
String statement = "com.johnny.personMapper.selectPersonById";
Person per = session.selectOne(statement,1);
System.out.println(per);
}
public static void selectAllPerson() throws IOException {
InputStream in = Resources.getResourceAsStream("config.xml");
SqlSessionFactory sqlFactory = new SqlSessionFactoryBuilder().build(in);
SqlSession session = sqlFactory.openSession();
String statement = "com.johnny.personMapper.selectAllPerson";
List<Person> per = session.selectList(statement);
System.out.println(per);
}
public static void addPerson() throws IOException {
InputStream in = Resources.getResourceAsStream("config.xml");
SqlSessionFactory sqlFactory = new SqlSessionFactoryBuilder().build(in);
SqlSession session = sqlFactory.openSession();
String statement = "com.johnny.personMapper.addPerson";
Person per = new Person(3, "ls", 55);
int count = session.insert(statement, per);
//提交事务
session.commit();
System.out.println("添加"+ count + "个人");
}
public static void updatePerson() throws IOException {
InputStream in = Resources.getResourceAsStream("config.xml");
SqlSessionFactory sqlFactory = new SqlSessionFactoryBuilder().build(in);
SqlSession session = sqlFactory.openSession();
String statement = "com.johnny.personMapper.updatePerson";
Person per = new Person();
per.setId(3);
per.setAge(36);
per.setName("lxs");
int count = session.update(statement, per);
session.commit();
System.out.println("修改"+ count + "个人");
}
public static void deletePerson() throws IOException {
InputStream in = Resources.getResourceAsStream("config.xml");
SqlSessionFactory sqlFactory = new SqlSessionFactoryBuilder().build(in);
SqlSession session = sqlFactory.openSession();
String statement = "com.johnny.personMapper.deletePersonById";
int count = session.delete(statement, 3);
//提交事务
session.commit();
System.out.println("删除"+ count + "个人");
}
public static void main(String[] args) throws IOException {
selectAllPerson();
// addPerson();
// updatePerson();
deletePerson();
selectAllPerson();
}
}
实体类person.java
package com.johnny.entity;
public class Person {
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 int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
@Override
public String toString() {
return this.id+"- "+ this.name+"- " +this.age;
}
public Person() {
}
public Person(String name, int age) {
this.name = name;
this.age = age;
}
public Person(int id,String name, int age) {
this.id = id;
this.name = name;
this.age = age;
}
private int id;
private String name;
private int age;
}
注意
如果使用事务方式为jdbc，则需要手动commit提交事务，即session.commit();