mybatis总结

mybatis总结"/>

mybatis总结

1.什么是Mybatis?

MyBatis是一个优秀的持久层框架，它对jdbc操作数据库的过程进行封装，使开发者只需要关注 SQL 本身，而不需要花费精力去处理例如注册驱动、创建connection、创建statement、手动设置参数、结果集检索等jdbc繁杂的过程代码。

Mybatis通过xml或注解的方式将要执行的各种statement（statement、preparedStatemnt、CallableStatement）配置起来，并通过java对象和statement中的sql进行映射生成最终执行的sql语句，最后由mybatis框架执行sql并将结果映射成java对象并返回。

2.为什么需要Mybatis?

帮助程序员将数据存入到数据库中。

方便：

传统的JDBC代码太复杂了。简化、框架、自动化。

不用Mybatis也可以。更容易上手。

优点：

简单易学灵活

sql和代码的分离，提高了可维护性。

提供映射标签，支持对象与数据库的orm字段关系映射

提供对象关系映射标签，支持对象关系组建维护

提供xml标签，支持编写动态sql。

• 单表的增删改查

代码

1.创建测试的数据库

use mydb;
CREATE TABLE classInfo(
cid int primary key auto_increment,
cname varchar(20),
cinfo varchar(20)
);
INSERT INTO classInfo(cname,cinfo) VALUES('移动212','普通班级');
INSERT INTO classInfo(cname,cinfo) VALUES('移动213','优秀班级');
INSERT INTO classInfo(cname,cinfo) VALUES('移动214','优秀班级');
SELECT *FROM classInfo;

2.创建一个Java项目并导入mybatis框架的jar包（在项目中创建一个lib文件夹放入mybatis框架的jar包，并导入项目中）

3.创建跟表对应的实体类（在src中创建com.yun.bean包，然后创建User实体类）

package com.yun.bean;public class User {private Integer cid;private  String cname;private  String  cinfo;public Integer getCid() {return cid;}public void setCid(Integer cid) {this.cid = cid;}public String getCname() {return cname;}public void setCname(String cname) {this.cname = cname;}public String getCinfo() {return cinfo;}public void setCinfo(String cinfo) {this.cinfo = cinfo;}@Overridepublic String toString() {return "User{" +"cid=" + cid +", cname='" + cname + '\'' +", cinfo='" + cinfo + '\'' +'}';}
}

4.创建针对表操作的接口类（在src中创建com.yun.dao包，然后创建UserDao的接口，然后在接口中定义针对数据库的增删改查等操作 ）

 package com.yun.dao;import com.yun.bean.User;import java.util.List;public interface UserDao {//根据id查询User selectByuid(int cid);//全查List<User> selectAll();//添加int add(User user);//删除int delete(int cid);//修改int update(User user);}

5.在接口的包中创建对应的mapper映射配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"".dtd">
<mapper namespace="com.yun.dao.UserDao"><select id="selectByuid" resultType="com.yun.bean.User">select * from classInfo where cid=#{cid};</select><select id="selectAll" resultType="com.yun.bean.User">select *from classInfo;</select><insert id="add" parameterType="com.yun.bean.User">insert into classInfo(cname,cinfo) values(#{cname},#{cinfo});</insert><delete id="delete" parameterType="int">delete from classInfo where cid=#{cid};</delete><update id="update" parameterType="com.yun.bean.User">update classInfo set cname=#{cname},cinfo=#{cinfo}where cid=#{cid};</update></mapper>

6.在src目录中创建mybatis框架的核心配置文件(打印日志输出)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configurationPUBLIC "-//mybatis.org//DTD Config 3.0//EN"".dtd">
<configuration><!--配置属性集,下面需要读取配置文件key对应的value--><properties resource="jdbc.properties" /><settings><!--配置项目使用log4j的日志输出--><setting name="logImpl" value="log4j"/></settings><typeAliases><!--        <typeAlias type="com.qi.bean.User" alias="user"></typeAlias>--><!--        <typeAlias type="java.lang.String" alias="string"></typeAlias>--><!--加载com.qi.bean包中所有的类，给类默认起别名为类的名字但首字母小写--><package name="com.yun.bean"/></typeAliases><environments default="mysql"><environment id="mysql"><transactionManager type="jdbc"></transactionManager><dataSource type="pooled"><property name="driver" value="${jdbc.driver}"/><property name="url" value="${jdbc.url}"/><property name="username" value="${jdbc.user}"/><property name="password" value="${jdbc.password}"/></dataSource></environment></environments><mappers><package name="com.yun.dao"/></mappers>
</configuration>

7.写入外部插件（在src里面创建log4j.properties）

log4j.rootLogger=TRACE,stdout  log4j.appender.stdout=org.apache.log4j.ConsoleAppender   
#log4j.appender.stdout.Target=System.err
log4j.appender.stdout.layout=org.apache.log4j.SimpleLayout   log4j.appender.logfile=org.apache.log4j.FileAppender   
log4j.appender.logfile.File=wocao.log   
log4j.appender.logfile.layout=org.apache.log4j.PatternLayout   
log4j.appender.logfile.layout.ConversionPattern=%d{yyyy-MM-dd HH:mm:ss} %F %p %m%n   
log4j.logger.mapperNS =TRACElog4j.logger.com.mybatis=DEBUG  
log4j.logger.com.mybatis.common.jdbc.SimpleDataSource=DEBUG   
log4j.logger.com.mybatis.common.jdbc.ScriptRunner=DEBUG   
log4j.logger.com.mybatis.sqlmap.engine.impl.SqlMapClientDelegate=DEBUG   
log4j.logger.java.sql.Connection=DEBUG  
log4j.logger.java.sql.Statement=DEBUG  
log4j.logger.java.sql.PreparedStatement=DEBUG  
log4j.logger.java.sql.ResultSet=DEBUG  log4j.logger.org.springframework=error 
log4j.logger.org.apache=ERROR  
log4j.logger.org.mybatis=DEBUG 

8.在src里面创建jdbc.properties

jdbc.driver=com.mysql.cj.jdbc.Driver
jdbc.url=jdbc:mysql://localhost:3306/mydb
jdbc.user=root
jdbc.password=root

9.在测试类中进行测试 （书写代码）

 package com.yun.test;import com.yun.bean.Stu;
import com.yun.bean.User;
import com.yun.dao.UserDao;
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 org.junit.After;
import org.junit.Before;
import org.junit.Test;import java.io.IOException;
import java.io.InputStream;
import java.util.List;public class UserText {InputStream stream=null;//字节输入流SqlSessionFactoryBuilder builder=null;//构建器对象SqlSessionFactory factory=null;//工厂对象SqlSession sqlSession=null;//sqlSession对象，用来完成jdbc操作UserDao userDao=null;//接口对接@Beforepublic void  init() throws IOException {stream= Resources.getResourceAsStream("mybatis.xml");builder=new SqlSessionFactoryBuilder();factory=builder.build(stream);sqlSession=factory.openSession();//根据类型创建对应的代理对象userDao=sqlSession.getMapper(UserDao.class);}//根据id查询@Testpublic void textselectByid(){User user=userDao.selectByuid(2);System.out.println(user);}//全查@Testpublic  void textselectAll(){List<User> userList=userDao.selectAll();for (User user:userList){System.out.println(user);}}//添加@Testpublic  void textadd() {User user=new User();user.setCname("xx");user.setCinfo("xx");int n=userDao.add(user);if(n>0){System.out.println("添加成功");}}//删除@Testpublic  void textdelete(){int del=userDao.delete(5);if (del>0){System.out.println("删除成功");}}//修改@Testpublic void textupdate(){User oldUser =userDao.selectByuid(3);System.out.println("修改前:"+oldUser);oldUser.setCname("移动214");oldUser.setCinfo("优秀班级");userDao.update(oldUser);User newUser=userDao.selectByuid(3);System.out.println("修改后:"+newUser);}@Afterpublic void distory() throws IOException {sqlSession.commit();sqlSession.close();stream.close();}
}

10.结果展示

• 全查

• 根据id查询

• 修改

• 添加

• 删除

• 两表联查 一对一

1.在bean包中创建实体类

public class Dept {private Integer did;private String dname;private String dinfo;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;}public String getDinfo() {return dinfo;}public void setDinfo(String dinfo) {this.dinfo = dinfo;}@Overridepublic String toString() {return "Dept{" +"did=" + did +", dname='" + dname + '\'' +", dinfo='" + dinfo + '\'' +'}';}
}

2.创建接口DeptDao实现根据id查询的接口

public interface DeptDao {Dept selectById(int did);
}

3.创建对应的mapper映射配置文件

    <select id="selectById" parameterType="int" resultType="com.qi.bean.Dept">select * from dept where did=#{did};</select>

4.在EmpDao中进行手动查询关联Dept,根据did查询创建查询id的接口

public interface EmpDao {Emp selectByEid(int eid);}

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"".dtd">
<!--namespace：把配置文件和接口进行映射-->
<mapper namespace="com.qi.dao.EmpDao"><!--定义手动映射关系:数据库中字段 和 类的属性 的映射--><resultMap id="empMap" type="emp"><id property="eid" column="eid"/><result property="ename" column="ename" /><result property="job" column="job" /><result property="sal" column="sal" /><result property="phone" column="phone" /><result property="address" column="address" /><!--一对一的映射配置association:配置emp中 dept对象中的属性和表字段的对应关系--><association column="did" select="com.qi.dao.DeptDao.selectById" property="dept"></association></resultMap><select id="selectByEid" parameterType="int" resultMap="empMap">select * from emp where eid=#{eid};</select>
</mapper>

5.进行测试（书写代码）

public class EmpTest {InputStream stream = null;SqlSessionFactoryBuilder builder = null;SqlSessionFactory factory = null;SqlSession sqlSession = null;EmpDao empDao= null;@Beforepublic void init() throws IOException {stream = Resources.getResourceAsStream("mybatis.xml");builder = new SqlSessionFactoryBuilder();factory = builder.build(stream);sqlSession = factory.openSession();empDao = sqlSession.getMapper(EmpDao.class);}@Testpublic void testSelectByeid(){Emp emp=empDao.selectByEid(2);System.out.println(emp);}@Afterpublic void destory() throws IOException {sqlSession.commit();sqlSession.close();stream.close();}
}

6.结果展示

• 两表联查 一对多

1.在Dept中创建集合

public class Dept {private Integer did;private String dname;private String dinfo;//一个部门包含多个员工，一对多关系就是定义集合List<Emp> emps;public List<Emp> getEmps() {return emps;}public void setEmps(List<Emp> emps) {this.emps = emps;}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;}public String getDinfo() {return dinfo;}public void setDinfo(String dinfo) {this.dinfo = dinfo;}@Overridepublic String toString() {return "Dept{" +"did=" + did +", dname='" + dname + '\'' +", dinfo='" + dinfo + '\'' +", emps=" + emps +'}';}
}

2.Emp实体类

package com.qi.bean;public class Emp {private Integer eid;private String ename;private String job;private double sal;private String phone;private String address;private Integer did;public Integer getDid() {return did;}public void setDid(Integer did) {this.did = did;}
//一对一关系的定义:把外键的did 定义为相关联的 对象public Integer getEid() {return eid;}public void setEid(Integer eid) {this.eid = eid;}public String getEname() {return ename;}public void setEname(String ename) {this.ename = ename;}public String getJob() {return job;}public void setJob(String job) {this.job = job;}public double getSal() {return sal;}public void setSal(double sal) {this.sal = sal;}public String getPhone() {return phone;}public void setPhone(String phone) {this.phone = phone;}public String getAddress() {return address;}public void setAddress(String address) {this.address = address;}@Overridepublic String toString() {return "Emp{" +"eid=" + eid +", ename='" + ename + '\'' +", job='" + job + '\'' +", sal=" + sal +", phone='" + phone + '\'' +", address='" + address + '\'' +", did=" + did +'}';}
}

3.根据did一对多查询在Dept接口中创建selectById方法

public interface DeptDao {Dept selectById(int did);
}

4.创建对应的mapper映射配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"".dtd">
<!--namespace：把配置文件和接口进行映射-->
<mapper namespace="com.qi.dao.DeptDao"><resultMap id="deptMap" type="com.qi.bean.Dept"><id property="did" column="did"/><id property="dname" column="dname"/><id property="dinfo" column="dinfo"/><!--配置一对多关系:自动根据did去关联查询emp表中该did的信息--><collection column="did" select="com.qi.dao.EmpDao.selectByDid" property="emps"></collection></resultMap><select id="selectById" parameterType="int" resultMap="deptMap">select * from dept where did=#{did};</select>
</mapper>

5.把查询的Dept中的值赋值给emps集合中 根据EmpDao中的did查询进行两表查询

public interface EmpDao {Emp selectByDid(int did);
}

6.对应的mapper映射配置文件

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"".dtd">
<!--namespace：把配置文件和接口进行映射-->
<mapper namespace="com.qi.dao.EmpDao"><!--定义手动映射关系:数据库中字段 和 类的属性 的映射--><select id="selectByDid" resultType="com.qi.bean.Emp">select * from emp where did=#{did};</select>
</mapper>

7.进行测试（书写代码）

public class DeptTest {InputStream stream = null;SqlSessionFactoryBuilder builder = null;SqlSessionFactory factory = null;SqlSession sqlSession = null;DeptDao deptDao= null;@Beforepublic void init() throws IOException {stream = Resources.getResourceAsStream("mybatis.xml");builder = new SqlSessionFactoryBuilder();factory = builder.build(stream);sqlSession = factory.openSession();deptDao = sqlSession.getMapper(DeptDao.class);}@Testpublic void testSelectByDid(){Dept dept = deptDao.selectById(101);System.out.println(dept);}@Afterpublic void destory() throws IOException {sqlSession.commit();sqlSession.close();stream.close();}
}

8.结果展示