iBATIS结果映射

以前使用的是hibernate的关系映射，换工作后新单位用dubbo框架，整个业务经常要使用ibatis结果集。进而针对ibatis的使用做个总结，好记心不如烂笔头，对自己的理解做个总结。

resultMap的元素是在iBATIS的最重要和最强大的元素。您可以通过使用iBATIS的结果映射减少高达90％的JDBC编码，在某些情况下，可以让你做JDBC不支持的事情。
ResultMaps的设计是这样的简单语句不需要明确的结果映射，以及更复杂的报表要求不超过绝对必要说明的关系。
本章将只给你一个简单的介绍iBATIS的结果映射。

在MySQL中创建EMPLOYEE表：

CREATE TABLE EMPLOYEE (
	id INT NOT NULL auto_increment,
	first_name VARCHAR(20) default NULL,
	last_name  VARCHAR(20) default NULL,
	salary  INT  default NULL,
	PRIMARY KEY (id)
);

EMPLOYEE表有如下两条记录：

mysql>select*from EMPLOYEE;
+----+------------+-----------+--------+
| id | first_name | last_name | salary |
+----+------------+-----------+--------+
|1|Zara|Ali|5000|
|2|HM|Ali|3000|
+----+------------+-----------+--------+
2 row inset(0.00 sec)

Employee POJO 类:

使用iBATIS的结果映射，需要修改Employee.java文件。

/**
 * Created by houxiurong on 2017/7/17.
 */
public class Employee {

    private int id;
    private String first_name;
    private String last_name;
    private int salary;

    /* Define constructors for the Employee class. */
    public Employee() {
    }

    public Employee(String fname, String lname, int salary) {
        this.first_name = fname;
        this.last_name = lname;
        this.salary = salary;
    }

    /* Here are the required method definitions */
    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getFirstName() {
        return first_name;
    }

    public void setFirstName(String fname) {
        this.first_name = fname;
    }

    public String getLastName() {
        return last_name;
    }

    public void setlastName(String lname) {
        this.last_name = lname;
    }

    public int getSalary() {
        return salary;
    }

    public void setSalary(int salary) {
        this.salary = salary;
    }
}

Employee.xml 文件:

在这里，我们将修改Employee.xml文件介绍标记。这个标签就必须在我们

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE sqlMap  PUBLIC "-//ibatis.apache.org//DTD SQL Map 2.0//EN"
                "http://ibatis.apache.org/dtd/sql-map-2.dtd">
<sqlMap namespace="Employee">

    <!-- Using ResultMap -->
    <resultMap id="result" class="Employee">
        <result property="id" column="id"/>
        <result property="first_name" column="first_name"/>
        <result property="last_name" column="last_name"/>
        <result property="salary" column="salary"/>
    </resultMap>

    <!-- Perform Insert Operation -->
    <insert id="insert" parameterClass="Employee">
        <selectKey resultClass="int" keyProperty="id">
            select last_insert_id() as id
        </selectKey>
        INSERT INTO EMPLOYEE(first_name, last_name, salary)
        VALUES(#first_name#, #last_name#, #salary#)
    </insert>

    <!-- Perform Read Operation -->
    <select id="getAll" resultClass="Employee">
        SELECT * FROM EMPLOYEE
    </select>

    <!-- Perform Update Operation -->
    <update id="update" parameterClass="Employee">
        UPDATE EMPLOYEE SET first_name = #first_name# WHERE id = #id#
    </update>

    <!-- Perform Delete Operation -->
    <delete id="delete" parameterClass="int">
        DELETE FROM EMPLOYEE WHERE id = #id#
    </delete>

    <select id="useResultMap" resultMap="result">
        SELECT * FROM EMPLOYEE WHERE id=#id#
    </select>
</sqlMap>

IbatisResultMap.java 文件:

文件将应用程序级别的逻辑，从使用结果映射Employee表中读取记录：

import com.ibatis.common.resources.Resources;
import com.ibatis.sqlmap.client.SqlMapClient;
import com.ibatis.sqlmap.client.SqlMapClientBuilder;
import java.io.*;
import java.sql.SQLException;
import java.util.*;

public class IbatisResultMap{

 public static void main(String[] args)throws IOException,SQLException{
   	Reader rd =Resources.getResourceAsReader("SqlMapConfig.xml");
   	SqlMapClient smc =SqlMapClientBuilder.buildSqlMapClient(rd);
   	int id =1;
   	System.out.println("Going to read record.....");
   	Employee e =(Employee)smc.queryForObject("Employee.useResultMap", id);
   	System.out.println("ID:  "+ e.getId());
   	System.out.println("First Name:  "+ e.getFirstName());
   	System.out.println("Last Name:  "+ e.getLastName());
   	System.out.println("Salary:  "+ e.getSalary());
   	System.out.println("Record read Successfully ");
   }
}

编译和运行：
下面是步骤来编译并运行上述程序。请确保您已在进行的编译和执行之前，适当地设置PATH和CLASSPATH。

• 创建Employee.xml如上所示。
• 创建Employee.java如上所示，并编译它。
• 创建IbatisResultMap.java如上所示，并编译它。
• 执行IbatisResultMap二进制文件来运行程序。
  会得到下面的结果是对EMPLOYEE表的读操作。

Going to read record..... 
ID:1 FirstName:Zara LastName:Ali Salary:5000 
Record read Successfully