iBATIS結果映射

resultMap的元素是在iBATIS的最重要和最強大的元素。您可以通過使用iBATIS的結果映射減少高達90％的JDBC編碼，在某些情況下，可以讓你做JDBC不支持的事情。

ResultMaps的設計是這樣的簡單語句不需要明確的結果映射，以及更復雜的報表要求不超過絕對必要說明的關系。

本章將只給你一個簡單的介紹iBATIS的結果映射。

我們已經在MySQL下有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)
);

此表有如下兩條記錄：

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)

Employee POJO 類:

使用iBATIS的結果映射，需要修改Employee.java文件。因此，讓我們保持它，因為它已經在前一章中使用過。

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:

在這裡，我們將修改Employee.xml文件介紹<resultMap></ resultMap>標記。這個標簽就必須在我們<select>標記的resultMap屬性運行此結果映射這是需要一個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:

文件將應用程序級別的邏輯，從使用結果映射Employee表中讀取記錄：

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 ");

  }
} 

編譯和運行：

下面是步驟來編譯並運行上述軟件。請確保您已在進行的編譯和執行之前，適當地設置PATH和CLASSPATH。

• 創建Employee.xml如上所示。

• 創建Employee.java如上圖所示，並編譯它。

• 創建IbatisResultMap.java如上圖所示，並編譯它。

• 執行IbatisResultMap二進制文件來運行程序。

會得到下面的結果是對EMPLOYEE表的讀操作。

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