iBATIS的結(jié)果映射

該resultMap元素是iBATIS的最重要和最強(qiáng)大的元素。您最多可以減少使用iBATIS的ResultMap 90％JDBC編碼，并在某些情況下，它可以讓你做的事情，JDBC甚至不支持。

ResultMaps的設(shè)計(jì)是這樣的簡(jiǎn)單語(yǔ)句根本不要求明確的結(jié)果映射，更復(fù)雜的語(yǔ)句需要不超過(guò)絕對(duì)必要說(shuō)明的關(guān)系。

本章只是一個(gè)簡(jiǎn)單的介紹iBATIS的ResultMaps的。

我們?cè)贛ySQL中下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)
);

這個(gè)表具有兩個(gè)記錄如下： -

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

員工PO??JO類(lèi)

要使用iBATIS的resultMap，但你并不需要修改Employee.java文件。讓我們保持它，因?yàn)樗窃谧詈笠徽隆?

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;
   }

} /* End of Employee */

Employee.xml文件

在這里，我們將修改Employee.xml介紹<resultMap的> </ resultMap的>標(biāo)記。這個(gè)標(biāo)簽本來(lái)這是需要我們的<select>標(biāo)記的結(jié)果映射屬性運(yùn)行此結(jié)果映射的ID。

<?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">

   <!-- Perform Insert Operation -->
	
   <insert id="insert" parameterClass="Employee">
      INSERT INTO EMPLOYEE(first_name, last_name, salary)
      values (#first_name#, #last_name#, #salary#)

      <selectKey resultClass="int" keyProperty="id">
         select last_insert_id() as id
      </selectKey>
   </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>

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

</sqlMap>

IbatisResultMap.java文件

這個(gè)文件的應(yīng)用程序級(jí)的邏輯讀取使用的ResultMap Employee表中的記錄 -

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 ");
   }
} 

編譯和運(yùn)行

以下是編譯并運(yùn)行上述軟件的步驟。請(qǐng)確保您已設(shè)置PATH和CLASSPATH在進(jìn)行適當(dāng)?shù)木幾g和執(zhí)行之前。

• 創(chuàng)建Employee.xml如上所示。
• 創(chuàng)建Employee.java如上圖所示，并對(duì)其進(jìn)行編譯。
• 創(chuàng)建IbatisResultMap.java如上圖所示，并對(duì)其進(jìn)行編譯。
• 執(zhí)行IbatisResultMap二進(jìn)制運(yùn)行程序。

你會(huì)得到以下結(jié)果這是對(duì)EMPLOYEE表讀操作。

Going to read record.....
ID:  1
First Name:  Zara
Last Name:  Ali
Salary:  5000
Record read Successfully