MyBatis学习笔记之注解式
1. 了解什么是MyBatis：
用百度的话来说，MyBatis 是一款优秀的持久层框架，它支持定制化 SQL、存储过程以及高级映射。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 可以使用简单的 XML 或注解来配置和映射原生信息，将接口和 Java 的 POJOs(Plain Ordinary Java Object,普通的 Java对象)映射成数据库中的记录。
简而言之，MyBatis是支持普通SQL查询，存储过程和高级映射的优秀持久层框架，MyBatis提供的是一种“半自动化”的ORM实现
2.简单例子：
在这里我们用的是IDEA开发工具，首先我们新建一个Maven项目
然后在pom.xml导入jar包：
mybatis需要jar包：mybatis-3.3.0.jar
mysql驱动jar包：mysql-connector-java-5.1.44.-bin.jar
日志记录jar包：log4j-1.2.17.jar
配置MyBatis映射文件mybatis.cfg.xml：
实体类：
City：
package com.zking.pojo;
import java.io.Serializable;
public class City extends Province implements Serializable{
private String cid;
private String cname;
private String pid;
//设置1对M关系
private Province province;
public City() {
}
public City(String cid, String cname, String pid) {
this.cid = cid;
this.cname = cname;
this.pid = pid;
}
public String getCid() {
return cid;
}
public void setCid(String cid) {
this.cid = cid;
}
public String getCname() {
return cname;
}
public void setCname(String cname) {
this.cname = cname;
}
public String getPid() {
return pid;
}
public void setPid(String pid) {
this.pid = pid;
}
public Province getProvince() {
return province;
}
public void setProvince(Province province) {
this.province = province;
}
}
Province：
package com.zking.pojo;
import java.io.Serializable;
import java.util.Set;
public class Province implements Serializable{
private String pid;
private String pname;
//设置关系 1V1
private City city;
//1VM
private Set sc;
public Province() {
}
public Province(String pid, String pname) {
this.pid = pid;
this.pname = pname;
}
public String getPid() {
return pid;
}
public void setPid(String pid) {
this.pid = pid;
}
public String getPname() {
return pname;
}
public void setPname(String pname) {
this.pname = pname;
}
public City getCity() {
return city;
}
public void setCity(City city) {
this.city = city;
}
public Set getSc() {
return sc;
}
public void setSc(Set sc) {
this.sc = sc;
}
}
创建方法接口：
package com.zking.mapper;
import com.zking.pojo.City;
import org.apache.ibatis.annotations.Delete;
import org.apache.ibatis.annotations.Insert;
import org.apache.ibatis.annotations.Select;
import org.apache.ibatis.annotations.Update;
import java.util.List;
public interface ICityMapper {
@Insert("insert into City values(#{cid},#{cname},#{pid})")
public int addCity(City city);
@Update("UPDATE City SET cname=#{cname},pid=#{pid} where cid=#{cid}")
public int editCity(City city);
@Delete("delete from City where cid=#{cid}")
public int removeCity(City city);
@Select("select * from City where pid=#{pid}")
public List finfCityAll();
}
package com.zking.mapper;
import com.zking.pojo.City;
import com.zking.pojo.Province;
import org.apache.ibatis.annotations.*;
import java.util.List;
public interface IProvinceMapper {
@Insert("INSERT INTO Province VALUES(#{pid},#{pname})")
public int addProvince(Province province);
@Update("UPDATE Province SET pname=#{pname} where pid=#{pid}")
public int editProvince(Province province);
//1V1关系注解
@Select("select * from Province")
@Results({
@Result(id = true,column = "pid",property = "pid"),
@Result(column = "pname",property = "pname"),
@Result(property = "city",column = "pid",
one=@One(select = "com.zking.mapper.ICityMapper.finfCityAll"))
})
public List findProvinceAll();
//多对多关系注解
@Select("select * from Province")
@Results({
@Result(id = true,column = "pid",property = "pid"),
@Result(column = "pname",property = "pname"),
@Result(property = "sc",column = "pid",
many=@Many(select = "com.zking.mapper.ICityMapper.finfCityAll"))
})
public List findProvinceAll2();
//动态SQL注解 作用在接口的方法上
@SelectProvider(type = ProvinceSqlBuilder.class,method = "findProvinceSql")
public List findProvinceAll3();
@SelectProvider(type = ProvinceSqlBuilder.class,method = "findProvinceByQuery")
public List findProvinceAll4(Province province);
@SelectProvider(type = ProvinceSqlBuilder.class,method = "findProvinceAll")
public List findProvinceAll5();
}
在MyBatis的映射配置文件中写sql语句有时候很方便，但是对于有大量字段的表结构却不太简单，幸好MyBatis提供的有SqlBuilder工具类，可以生成相应的SQL语句，如下：
package com.zking.mapper;
import com.zking.pojo.Province;
import org.apache.ibatis.jdbc.SQL;
public class ProvinceSqlBuilder {
public String findProvinceSql(){
return new SQL()
.SELECT("*")
.FROM("Province")
.toString();
}
public String findProvinceByQuery(final Province province){
return new SQL(){{
SELECT("*");
FROM("Province");
if(province.getPname()!=null){
AND();
WHERE("pname like #{pname}");
}
}}.toString();
}
public String findProvinceAll(){
return new SQL(){{
SELECT("*");
FROM("Province p");
LEFT_OUTER_JOIN(" City c on p.pid=c.pid");
}}.toString();
}
}
测试类：
package com.zking.test;
import com.zking.mapper.ICityMapper;
import com.zking.mapper.IProvinceMapper;
import com.zking.pojo.City;
import com.zking.pojo.Province;
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.Test;
import java.util.List;
import java.util.UUID;
public class MyBatis04Test {
@Test
public void addProvince() throws Exception{
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
IProvinceMapper ipm = sqlSession.getMapper(IProvinceMapper.class);
Province p=new Province();
p.setPid(String.valueOf(UUID.randomUUID()));
p.setPname("湖北");
ipm.addProvince(p);
sqlSession.commit();
sqlSession.close();
}
@Test
public void editProvince() throws Exception{
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
IProvinceMapper ipm = sqlSession.getMapper(IProvinceMapper.class);
Province p=new Province();
p.setPid("044ff20a-9da1-4205-a75a-991b6bfb413f");
p.setPname("湖北");
ipm.editProvince(p);
sqlSession.commit();
sqlSession.close();
}
@Test
public void addCity() throws Exception{
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
ICityMapper icm = sqlSession.getMapper(ICityMapper.class);
City c=new City();
c.setCid(String.valueOf(UUID.randomUUID()));
c.setCname("株洲");
c.setPid("5894c3bf-f89c-4dca-810c-64c5c25da742");
icm.addCity(c);
sqlSession.commit();
sqlSession.close();
}
@Test
public void editCity() throws Exception{
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
ICityMapper icm = sqlSession.getMapper(ICityMapper.class);
City c=new City();
c.setCid("441c77ef-80aa-4327-9fd7-e1f08c92292b");
c.setCname("长沙");
c.setPid("5894c3bf-f89c-4dca-810c-64c5c25da742");
icm.editCity(c);
sqlSession.commit();
sqlSession.close();
}
@Test
public void removeCity() throws Exception{
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
ICityMapper icm = sqlSession.getMapper(ICityMapper.class);
City c=new City();
c.setCid("521b672e-0109-432b-ae92-cc75323ea3fc");
icm.removeCity(c);
sqlSession.commit();
sqlSession.close();
}
@Test
public void findProvinceAll() throws Exception{
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
IProvinceMapper ipm = sqlSession.getMapper(IProvinceMapper.class);
ipm.findProvinceAll();
sqlSession.commit();
sqlSession.close();
}
@Test
public void findProvinceAll2() throws Exception{
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
IProvinceMapper ipm = sqlSession.getMapper(IProvinceMapper.class);
ipm.findProvinceAll2();
sqlSession.commit();
sqlSession.close();
}
@Test
public void findProvinceAll3() throws Exception{
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
IProvinceMapper ipm = sqlSession.getMapper(IProvinceMapper.class);
ipm.findProvinceAll3();
sqlSession.commit();
sqlSession.close();
}
@Test
public void findProvinceAll4() throws Exception{
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
IProvinceMapper ipm = sqlSession.getMapper(IProvinceMapper.class);
Province province=new Province();
province.setPname("%南%");
ipm.findProvinceAll4(province);
sqlSession.commit();
sqlSession.close();
}
@Test
public void findProvinceAll5() throws Exception{
SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(Resources.getResourceAsStream("mybatis-config.xml"));
SqlSession sqlSession = sqlSessionFactory.openSession();
IProvinceMapper ipm = sqlSession.getMapper(IProvinceMapper.class);
List list = ipm.findProvinceAll5();
for (City c : list) {
System.out.println(c.getPname()+"---"+c.getCname());
}
sqlSession.commit();
sqlSession.close();
}
}
其实MyBatis的注解式如果说是单一的Crud可能比较简便，但是在动态SQL部分就比较麻烦，所以更建议使用配置式。