MyBatis之CRUD

1 mybatis框架介绍

1.1回顾jdbc操作数据库的过程

1.2 mybatis开发步骤

A．提供一个SqlMapperConfig.xml(src目录下)，该文件主要配置数据库连接，事务,二级缓存。

B.提供一个XxxMapper.xml(DeptMapper.xml),放入和DeptDao同一个包中。

Sql语句

Sql语句占位符的值

Sql语句执行后需要返回的结果类型

C.使用mybatis提供的API操作数据库。

Mybatis完成对jdbc的封装，将操作数据过程需要的参数，封装到xml文件中，做到了可变的参数和不可变的代码的之间的解耦合，提高数据库开的效率。

2 Mybatis对数据的CRUD

2.1新建项目加入jar包

2.2建立Mybatis的主配置文件

必须放入src目录（classpath）

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">
 <configuration>
   <properties resource="db.properties"></properties>
      <environments default="deptEnv">
         <environment id="deptEnv">
             <transactionManager type="JDBC" />
             <dataSource type="POOLED">
                 <property name="driver" value="${driver}" />
                 <property name="url" value="${url}" />
                 <property name="username" value="${username}" />
                 <property name="password" value="${password}" />
             </dataSource>
         </environment>
     </environments>
     <mappers>
         <mapper resource="org/guangsoft/mapper/DeptMapper.xml" />
     </mappers>
 </configuration>

db.properties

 driver = com.mysql.jdbc.Driver
 url = jdbc:mysql://localhost:3306/test
 username = root
 password =root

2.3建立部门的实体类

 package org.guangsoft.entity;

 public class Dept
 {
     private Integer did;
     private String dname;
     public Integer getDid()
     {
         return did;
     }
     public void setDid(Integer did)
     {
         this.did = did;
     }
     public String getDname()
     {
         return dname;
     }
     public void setDname(String dname)
     {
         this.dname = dname;
     }

 }

2.4建立DeptMapper接口

 package org.guangsoft.mapper;

 import java.util.List;

 import org.guangsoft.entity.Dept;

 public interface DeptMapper
 {
     public void saveDept(Dept dept);
     public void deleteDept(Integer did);
     public void updateDept(Dept dept);
     public Dept getDeptById(Integer did);
     public List<Dept> getAllDepts();
     public Integer getDeptCount();
 } 

2.5建立DeptMapperImpl实现类

使用Mybatis的API完成数据库添加

 package org.guangsoft.mapper.impl;

 import java.util.List;

 import org.apache.ibatis.session.SqlSession;
 import org.apache.ibatis.session.SqlSessionFactory;
 import org.apache.ibatis.session.SqlSessionFactoryBuilder;
 import org.guangsoft.entity.Dept;
 import org.guangsoft.mapper.DeptMapper;

 public class DeptMapperImpl implements DeptMapper
 {

     @Override
     public void saveDept(Dept dept)
     {
         //创建sqlSessionFactory对象
         SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
         SqlSessionFactory ssf = ssfb.build(DeptMapperImpl.class.
                     getClassLoader().getResourceAsStream("MyBatis.xml"));
         //产生SqlSesion兑现
         SqlSession sqlSession = ssf.openSession();
         //进行数据的crud操作
         sqlSession.insert("dept.saveDept",dept);
         //提交事务
         sqlSession.commit();
         //释放资源
         sqlSession.close();
     }

     @Override
     public void deleteDept(Integer did)
     {
         //创建sqlSessionFactory对象
         SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
         SqlSessionFactory ssf = ssfb.build(DeptMapperImpl.class.
                 getClassLoader().getResourceAsStream("MyBatis.xml"));
         //产生SqlSesion兑现
         SqlSession sqlSession = ssf.openSession();
         //进行数据的crud操作
         int rows = sqlSession.delete("dept.deleteDept",did);
         //提交事务
         sqlSession.commit();
         //释放资源
         sqlSession.close();
     }

     @Override
     public void updateDept(Dept dept)
     {
         //创建sqlSessionFactory对象
         SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
         SqlSessionFactory ssf = ssfb.build(DeptMapperImpl.class.
                 getClassLoader().getResourceAsStream("MyBatis.xml"));
         //产生SqlSesion兑现
         SqlSession sqlSession = ssf.openSession();
         //进行数据的crud操作
         int rows = sqlSession.update("dept.updateDept",dept);
         //提交事务
         sqlSession.commit();
         //释放资源
         sqlSession.close();
     }

     @Override
     public Dept getDeptById(Integer did)
     {
         SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
         SqlSessionFactory ssf = ssfb.build(DeptMapperImpl.class.getClassLoader().getResourceAsStream("MyBatis.xml"));
         //获取数据库会话
         SqlSession session = ssf.openSession();
         //进行数据库查询操作
         Dept dept = session.selectOne("dept.getDeptById",did);
         //释放资源
         session.close();
         return dept;
     }

     @Override
     public List<Dept> getAllDepts()
     {
         SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
         SqlSessionFactory ssf = ssfb.build(DeptMapperImpl.class.getClassLoader().getResourceAsStream("MyBatis.xml"));
         //获取数据库会话
         SqlSession session = ssf.openSession();
         //进行数据库查询操作
         List<Dept> deptList = session.selectList("dept.getAllDepts");
         //释放资源
         session.close();
         return deptList;
     }

     @Override
     public Integer getDeptCount()
     {
         SqlSessionFactoryBuilder ssfb = new SqlSessionFactoryBuilder();
         SqlSessionFactory ssf = ssfb.build(DeptMapperImpl.class.getClassLoader().getResourceAsStream("MyBatis.xml"));
         //获取数据库会话
         SqlSession session = ssf.openSession();
         //进行数据库查询操作
         int count = session.selectOne("dept.getDeptCount");
         //释放资源
         session.close();
         return count;
     }

 }

2.6建立映DeptMapper.xml射文件

和Mapper接口放入同一个包，而且和Mapper接口的名字一样。

 <?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE mapper PUBLIC "-//mybatis.org/DTD Mapper 3.0" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
 <mapper namespace="dept">
     <insert id="saveDept" parameterType="org.guangsoft.entity.Dept">
         insert into dept(did,dname) values (null,#{dname})
         <selectKey keyColumn="did" keyProperty="did" resultType="java.lang.Integer">
             <!-- 获得增加的记录的id -->
             select last_insert_id()
         </selectKey>
     </insert>
     <delete id="deleteDept" parameterType="java.lang.Integer">
         delete from dept where did = #{did};
     </delete>
     <update id="updateDept" parameterType="org.guangsoft.entity.Dept">
         update dept set dname = #{dname} where did=#{did}
     </update>
     <select id="getDeptById" parameterType="java.lang.Integer"
         resultType="org.guangsoft.entity.Dept">
         select * from dept where did = #{did}
     </select>
     <select id="getAllDepts" resultType="org.guangsoft.entity.Dept">
         select * from dept
     </select>
     <select id="getDeptCount" resultType="java.lang.Integer">
         select count(*) from dept
     </select>
 </mapper>

2.7建立数据库表

新建数据库,新建表：

 /*
 Navicat MySQL Data Transfer

 Source Server         : MySQL
 Source Server Version : 50715
 Source Host           : localhost:3306
 Source Database       : test

 Target Server Type    : MYSQL
 Target Server Version : 50715
 File Encoding         : 65001

 Date: 2016-12-13 20:23:19
 */

 SET FOREIGN_KEY_CHECKS=0;

 -- ----------------------------
 -- Table structure for dept
 -- ----------------------------
 DROP TABLE IF EXISTS `dept`;
 CREATE TABLE `dept` (
   `did` int(11) NOT NULL AUTO_INCREMENT,
   `dname` varchar(255) DEFAULT NULL,
   PRIMARY KEY (`did`)
 ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8;

2.8建立测试类

 package org.guangsoft.test;

 import java.util.List;

 import org.guangsoft.entity.Dept;
 import org.guangsoft.mapper.DeptMapper;
 import org.guangsoft.mapper.impl.DeptMapperImpl;
 import org.junit.Test;

 public class TestDeptMapper
 {
     DeptMapper deptMapper = new DeptMapperImpl();

     @Test
     public void testSaveDept()
     {
         Dept dept = new Dept();
         dept.setDname("sssssdfs");
         deptMapper.saveDept(dept);
         System.out.println(dept.getDid());
     }

     @Test
     public void testDeleteDept()
     {
         deptMapper.deleteDept(3);
     }

     @Test
     public void testUpdateDept()
     {
         Dept dept = new Dept();
         dept.setDid(2);
         dept.setDname("update");
         deptMapper.updateDept(dept);
     }

     @Test
     public void testGetDeptById()
     {
         Dept dept = deptMapper.getDeptById(2);
         System.out.println(dept.getDname());
     }

     @Test
     public void testGetAllDepts()
     {
         List<Dept> deptList = deptMapper.getAllDepts();
         for(Dept dept : deptList)
         {
             System.out.println(dept.getDname());
         }
     }

     @Test
     public void testGetDeptCount()
     {
         Integer count = deptMapper.getDeptCount();
         System.out.println(count);
     }
 }

2.9添加日志文件

在src目录下建立，log4j.properties

 # Global logging configuration
 log4j.rootLogger=DEBUG, stdout
 # MyBatis logging configuration...
 log4j.logger.org.mybatis.example.BlogMapper=TRACE
 # Console output...
 log4j.appender.stdout=org.apache.log4j.ConsoleAppender
 log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
 log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n 

总结:mybatis框架通过加载配置文件产生一个statement对象，而该对象的引用是通过namespace.id

3 数据选择的Mapper.xml配置参数

3.1 通过添加部门信息学习xml文件中的占位符

3.1.1#{xxx}占位符

相当于jdbc中sql语句预编译.(产生PreparedStatement对象)，解决了sql注入的问题，提高安全性。

如果传入的参数为javabean对象占位符#{xxx}，

xxx为javabean对象属性对应的get方法

如果为复合的javabean（A.B）,

xxx为javabean对象属性链（b.x），相应属性都对应get方法

如果传入的参数为简单类（String,Integer）

xxx为任意值，保持和传入参数名称一样

3.1.2${xxx}占位符

相当于jdbc中的sql语句通过拼接产生（产生Statement对象），存在sql注入的问题

如果传入的参数为javabean对象占位符#{xxx}，

xxx为javabean对象属性对应的get方法

如果为复合的javabean（A.B）,

xxx为javabean对象属性链（b.x），相应属性都对应get方法

如果传入的参数为简单类（String,Integer）

xxx只能写value