MyBatis具体使用方式 - 《教有缘人学 Java 教程》

定义Dao接口并实现其接口
只定义Dao接口，利用SqlSession的getMapper方法生成Dao的代理对象

查询数据库的操作是放在Dao层的,在Dao层我们有以下3种方式使用MyBatis进行数据库的操作。

定义Dao接口并实现其接口

对《SQL必知必会》里面的客户表进行操作。

JavaBean

package com.lff;
public class Customers {
    private Integer custId;
    private String custName;
    private String custAddress;
    private String custCity;
    private String custState;
    private String custZip;
    private String custCountry;
    private String custContact;
    private String custEmail;
   //setter and getter....
}

mapper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">
<mapper namespace="customers">
    <insert id="add" parameterType="com.lff.Customers">
        INSERT INTO Customers(cust_id,cust_name,cust_address,cust_city,cust_state,cust_zip) values (#{custId},#{custName},#{custAddress},#{custCity},#{custState},#{custZip})
    </insert>
    <delete id="delete" parameterType="int">
        DELETE FROM Customers WHERE cust_id = #{id}
    </delete>
    <update id="save" parameterType="com.lff.Customers">
        UPDATE Customers SET cust_name=#{custName},cust_address = #{custAddress},cust_city=#{custCity},cust_state=#{custState},cust_zip=#{custZip} where cust_id = #{custId}
    </update>
    <select id="selectOneCustomer" parameterType="int" resultType="com.lff.Customers">
        SELECT * FROM Customers WHERE cust_id = #{id}
    </select>
</mapper>

DAO接口

package com.lff.dao;
import com.lff.Customers;
public interface CustomerDaoInterface {
    public Boolean add(Customers customers); //增
    public boolean delete(Integer id); //删
    public boolean save(Customers customers); //改
    public Customers selectOneCustomer(Integer id); //查
}

Dao实现类

在实现类里面获取到SqlSession对象，进行数据库操作

package com.lff.dao;
import com.lff.Customers;
import com.lff.beans.Person;
import org.apache.ibatis.session.SqlSession;
import utils.MyBatisUtils;
import java.util.List;
public class CustomerDaoImpl implements CustomerDaoInterface{
    @Override
    public Boolean add(Customers customers) {
        Integer effectRows;
        try(SqlSession session = MyBatisUtils.openSession()){
            effectRows = session.insert("customers.add",customers);
            session.commit();
        }
        return effectRows > 0;
    }
    @Override
    public boolean delete(Integer id) {
        Integer effectRows;
        try(SqlSession session = MyBatisUtils.openSession()){
            effectRows = session.delete("customers.delete",id);
            session.commit();
        }
        return effectRows > 0;
    }
    @Override
    public boolean save(Customers customers) {
        Integer effectRows;
        try(SqlSession session = MyBatisUtils.openSession()){
            effectRows = session.update("customers.save",customers);
            session.commit();
        }
        return effectRows > 0;
    }
    @Override
    public Customers selectOneCustomer(Integer id) {
        Customers  Customers;
        try(SqlSession session = MyBatisUtils.openSession()){
            Customers = session.selectOne("customers.selectOneCustomer",id);
        }
        return Customers;
    }
}

外界使用

//增
Customers customers1 = new Customers();
customers1.setCustId(160);
customers1.setCustName("lff");
customers1.setCustState("ss");
customers1.setCustCity("BJ");
customers1.setCustState("CN");
customers1.setCustZip("10001");
CustomerDaoInterface dao =  new CustomerDaoImpl();
dao.add(customers1);

//删
CustomerDaoInterface dao =  new CustomerDaoImpl();
dao.delete(160);

//改
Customers customers1 = new Customers();
customers1.setCustId(1011);
customers1.setCustName("lifufa");
customers1.setCustState("ss");
customers1.setCustCity("BJ");
customers1.setCustState("CN");
customers1.setCustZip("10001");
dao.save(customers1);

//查
Customers customers = dao.selectOneCustomer(0);

只定义Dao接口，利用SqlSession的getMapper方法生成Dao的代理对象

第一步：先写Dao接口

package com.lff.dao;
import com.lff.Customers;
public interface CustomerDaoInterface {
    public Boolean add(Customers customers); //增
    public boolean delete(Integer id); //删
    public boolean save(Customers customers); //改
    public Customers selectOneCustomer(Integer id); //查
}

�第二步：在mapper文件里面要求有两点

namespace的名称要为Dao接口类的全类名
select、insert、update、delete的id值要与Dao接口中的方法名保持一致 ```xml <?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 Customers(cust_id,cust_name,cust_address,cust_city,cust_state,cust_zip) values (#{custId},#{custName},#{custAddress},#{custCity},#{custState},#{custZip}) DELETE FROM Customers WHERE cust_id = #{id} UPDATE Customers SET cust_name=#{custName},cust_address = #{custAddress},cust_city=#{custCity},cust_state=#{custState},cust_zip=#{custZip} where cust_id = #{custId}

�外界使用
```java
//增
Customers customers1 = new Customers();
customers1.setCustId(160);
customers1.setCustName("lff");
customers1.setCustState("ss");
customers1.setCustCity("BJ");
customers1.setCustState("CN");
customers1.setCustZip("10001");
try(SqlSession session = MyBatisUtils.openSession()){
    //使用该方式生成Dao接口的代理对象
    CustomerDaoInterface customerDao = session.getMapper(CustomerDaoInterface.class);
    customerDao.add(customers1);
    session.commit();
}

使用上面的方式生成Dao的代理对象后，就可以使用该对象里面的方法，进行增、删、改、查啦。

//删除
try(SqlSession session = MyBatisUtils.openSession()){
    //使用该方式生成Dao接口的代理对象
    CustomerDaoInterface customerDao = session.getMapper(CustomerDaoInterface.class);
     Boolean isSuccess =  customerDao.delete(160); //应该返回影响的行数，但MyBatis内部会判断如果Dao方法名中返回的是Boolean值就做y影响行数>0处理。
    session.commit();
}