MyBatis（一）

MyBatis

简介

什么是 MyBatis ？

MyBatis 是支持定制化 SQL、存储过程以及高级映射的优秀的持久层框架。MyBatis 避免了几乎所有的 JDBC 代码和手动设置参数以及获取结果集。MyBatis 可以对配置和原生Map使用简单的 XML 或注解，将接口和 Java 的 POJOs(Plain Old Java Objects,普通的 Java对象)映射成数据库中的记录，且是ibatis的进一步完善和升级。

XML 配置文件（configuration XML）中包含了对 MyBatis 系统的核心设置，包含获取数据库连接实例的数据源（DataSource）和决定事务作用域和控制方式的事务管理器（TransactionManager）。

environment 元素体中包含了事务管理和连接池的配置。mappers 元素则是包含一组 mapper 映射器（这些 mapper 的 XML 文件包含了 SQL 代码和映射定义信息）。

Mybatis案例

导包：

表的实体User

package mybatis.model;

public class User {

private int id;

private String username;

private String password;

public int getId() {

return id;}

public void setId(int id) {

this.id = id;}

public String getUsername() {

return username;}

public void setUsername(String username) {

this.username = username;}

public String getPassword() {

return password;}

public void setPassword(String password) {

this.password = password;}

public User() {}

public User( String username, String password) {

this.username = username;

this.password = password;}

@Override

public String toString() {

return "User [id=" + id + ", username=" + username + ", password="

+ password + "]";}}

Mybatis配置文件

<?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">

</dataSource>

</environment>

</environments>

</mappers>

</configuration>

Mybatis文件的映射文件（具体操作）

<?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">

<!—如这边需要两个参数，需要指定值的对应所以选用map集合-->

insert into user(username,password)

values(#{username},#{password})

</insert>

update user set username=#{username},password=#{password} where id=#{id}

</update>

delete from user where id=#{id}

</delete>

select *from user where id= #{id}

</select>

select *from user

</select>

select *from user limit #{0ffSet},#{pageSize}

</select>

select *from user order by ${order} ${sort} limit #{0ffSet},#{pageSize}

</select>

</mapper>

Test测试

package mybatis.mapper.Test;

import java.io.IOException;

import java.io.InputStream;

import java.util.HashMap;

import java.util.Map;

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 Test {

@org.junit.Test

public void Test() throws IOException{

//加载配置文件

InputStream is= Resources.getResourceAsStream("mybatis.xml");

//获取sqlsessionFactory

SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);

//获取sqlsession和打开

SqlSession session= factory.openSession();

//执行操作

Map<String, Object> params=new HashMap<String,Object>();

params.put("username","asd");

params.put("password","asd");

session.insert("mybatis.model.User.add",params);

//提交事务

session.commit();

}

//测试添加

@org.junit.Test

public void Test2() throws IOException{

//加载配置文件

InputStream is= Resources.getResourceAsStream("mybatis.xml");

//获取sqlsessionFactory

SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);

//获取sqlsession和打开

SqlSession session= factory.openSession();

//执行操作

Map<String, Object> params=new HashMap<String,Object>();

params.put("username","asd");

params.put("password","asdasd");

params.put("id", "3");

session.update("mybatis.model.User.update",params);

//提交事务

session.commit();

}

@org.junit.Test

public void del() throws IOException{

InputStream is = Resources.getResourceAsStream("mybatis.xml");

SqlSessionFactory factory = new SqlSessionFactoryBuilder().build(is);

SqlSession session = factory.openSession();

session.delete("mybatis.model.User.del",4);

session.commit();

}

因为里面有一些重复的代码所以，可以将一些操作提取出来

工具类;

package mybatis.until;

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;

/**

* @author lx

public class BasDao {

static SqlSessionFactory factory=null;

static{

//加载配置文件

InputStream is;

try {

is = Resources.getResourceAsStream("mybatis.xml");

factory = new SqlSessionFactoryBuilder().build(is);

} catch (IOException e) {

e.printStackTrace();

}

/**

* 打开session

* @return

public static SqlSession getSession(){

return factory.openSession();

}

/**

* 关闭session

public static void close(SqlSession session){

if(session !=null){

session.close();

}

Test测试：

package mybatis.mapper.Test;

import java.util.HashMap;

import java.util.Map;

import mybatis.model.User;

import mybatis.until.BasDao;

import org.apache.ibatis.session.SqlSession;

import org.junit.Test;

public class myTest {

@Test

public void add(){

//获取session

SqlSession session = BasDao.getSession();

//设置参数

Map<String, Object> params=new HashMap<String,Object>();

params.put("username","asd");

params.put("password","asd");

//执行操作

session.insert("mybatis.model.User.add",params);

//提交事务

session.commit();

//关闭资源

BasDao.close(session);

}

@Test

public void update(){

Map<String, Object> params=new HashMap<String,Object>();

//获取session

SqlSession session = BasDao.getSession();

//设置参数

params.put("username","asd");

params.put("password","asdasd");

params.put("id", "6");

//获取的和mybatis.model.User.update第一样

session.update(User.class.getName()+".update",params);

//提交事务

session.commit();

//关闭资源

BasDao.close(session);

}

@Test

public void del(){

//获取session

SqlSession session = BasDao.getSession();

session.delete(User.class.getName()+".del",6);

//提交事务

session.commit();

//关闭资源

BasDao.close(session);

}

Test：查询的测试：

package mybatis.mapper.Test;

import java.util.HashMap;

import java.util.List;

import java.util.Map;

import mybatis.model.User;

import mybatis.until.BasDao;

import org.apache.ibatis.session.SqlSession;

import org.junit.Test;

public class TestSelect {

/**

* 简单查询，对于单个对象的查询

@Test

public void testload(){

SqlSession session = BasDao.getSession();

User user = session.selectOne(User.class.getName()+".load",2);

System.out.println(user);

BasDao.close(session);

}

/**

* 查询表中所有的信息

@Test

public void testlist(){

SqlSession session = BasDao.getSession();

List<User> users = session.selectList(User.class.getName()+".list");

for(User u:users){

System.out.println(u);

}

BasDao.close(session);

}

/**

* 查询分页

@Test

public void testfen(){

SqlSession session = BasDao.getSession();

Map<String,Object> map = new HashMap<String ,Object>();

map.put("0ffSet", 0);

map.put("pageSize", 3);

List<User> users = session.selectList(User.class.getName()+".pagelist",map);

for(User u:users){

System.out.println(u);

}

BasDao.close(session);

}

/**

* 分页排序查询

@Test

public void testfenfenzu(){

SqlSession session = BasDao.getSession();

Map<String,Object> map = new HashMap<String ,Object>();

map.put("0ffSet", 0);

map.put("order","id");

map.put("sort", "desc");

map.put("pageSize", 4);

List<User> users = session.selectList(User.class.getName()+".page",map);

for(User u:users){

System.out.println(u);

}

BasDao.close(session);

}

#:根据参数类型来设置

$:直接使用参数，不进行任何的转义，有sql注入的风险

properties

这些属性都是可外部配置且可动态替换的，既可以在典型的 Java 属性文件中配置，亦可通过 properties 元素的子元素来传递

typeAliases

类型别名是为 Java 类型设置一个短的名字。它只和 XML 配置有关，存在的意义仅在于用来减少类完全限定名的冗余。

更改3

Mybaits:

<?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">

</typeAliases>

</dataSource>

</environment>

</environments>

</mappers>

</configuration>

映射文件

<?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">

insert into user(username,password)

values(#{username},#{password})

</insert>

update user set username=#{username},password=#{password} where id=#{id}

</update>

delete from user where id=#{id}

</delete>

select *from user where id= #{id}

</select>

select *from user

</select>

select *from user limit #{0ffSet},#{pageSize}

</select>

select *from user order by ${order} ${sort} limit #{0ffSet},#{pageSize}

</select>

</mapper>

基于接口的实现

映射器（mappers）

既然 MyBatis 的行为已经由上述元素配置完了，我们现在就要定义 SQL 映射语句了。但是首先我们需要告诉 MyBatis 到哪里去找到这些语句。 Java 在自动查找这方面没有提供一个很好的方法，所以最佳的方式是告诉 MyBatis 到哪里去找映射文件。你可以使用相对于类路径的资源引用，或完全限定资源定位符（包括 file:/// 的 URL），或类名和包名等

UserMapper接口

package mybatis.ma;

import java.util.List;

import mybatis.model.User;

public interface UserMapper {

/**

* 接口中的方法与usermapper.xml文件 id相对应

void add(User user);

void update(User user);

void del(int id);

public User load(int id);

public List<User>list();

public List<User>pagelist();

public List<User>page();

public int count();}

Usermapper.xml映射文件：

<?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">

insert into user(username,password)

values(#{username},#{password})

</insert>

update user set username=#{username},password=#{password} where id=#{id}

</update>

delete from user where id=#{id}

</delete>

select *from user where id= #{id}

</select>

select *from user

</select>

select *from user limit #{0ffSet},#{pageSize}

</select>

select *from user order by ${order} ${sort} limit #{0ffSet},#{pageSize}

</select>

select count(*) from user

</select>

</mapper>

Mybatis.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">

</typeAliases>

</dataSource>

</environment>

</environments>

</mappers>

</configuration>

测试：

package mybatistwo.UserImp;

import java.util.List;

import mybatistwo.BasDao.UserDao;

import mybatistwo.mapper.UserMapper;

import mybatistwo.model.User;

import org.apache.ibatis.session.SqlSession;

import org.junit.Test;

public class UserImp {

/**

* 用户个数统计

@Test

public void Testcount(){

SqlSession session = UserDao.getSession();

int i = session.getMapper(UserMapper.class).count();

System.out.println(i);

UserDao.close(session);

}

/**

* 添加

@Test

public void TESADD(){

SqlSession session = UserDao.getSession();

User user = new User("冬","asdas");

session.getMapper(UserMapper.class).add(user);

session.commit();

UserDao.close(session);

}

/**

* 更改

@Test

public void TESupdate(){

SqlSession session = UserDao.getSession();

User user = new User();

user.setId(8);

user.setPassword("ass");

user.setUsername("asdasd");

session.getMapper(UserMapper.class).update(user);

session.commit();

UserDao.close(session);

}

/**

* 删除

@Test

public void TESdel(){

SqlSession session = UserDao.getSession();

session.getMapper(UserMapper.class).del(7);

session.commit();

UserDao.close(session);

}

/**

* 查询单个对象

@Test

public void TESelect(){

SqlSession session = UserDao.getSession();

User user = session.getMapper(UserMapper.class).load(2);

System.out.println(user);

UserDao.close(session);

}

/**

* 查询所有用户

@Test

public void TElist(){

SqlSession session = UserDao.getSession();

List<User> list = session.getMapper(UserMapper.class).list();

for(User u:list){

System.out.println(u);

}

UserDao.close(session);

}