iBATIS的讀操作

我們討論，在最后一章，如何執(zhí)行創(chuàng)建使用iBATIS表操作。本章介紹如何使用iBATIS讀取表。

我們在MySQL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)
);

此表只有一個記錄如下 -

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

員工PO??JO類

要執(zhí)行讀操作，我們將修改Employee類中Employee.java如下 -

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 method definitions */
   public int getId() {
      return id;
   }
	
   public String getFirstName() {
      return first_name;
   }
	
   public String getLastName() {
      return last_name;
   }
	
   public int getSalary() {
      return salary;
   }
	
} /* End of Employee */

Employee.xml文件

要定義使用iBATIS SQL映射語句中，我們將增加的<select>在Employee.xml文件，這個標簽定義標記內(nèi)，我們將定義將在IbatisRead.java文件中，用于對數(shù)據(jù)庫執(zhí)行SQL SELECT查詢的“身份證”。

<?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">

   <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>
	
   <select id="getAll" resultClass="Employee">
      SELECT * FROM EMPLOYEE
   </select>
	
</sqlMap>

在這里，我們沒有使用WHERE子句與SQL SELECT語句。我們將證明，在接下來的章節(jié)中，你怎么能與WHERE SELECT語句子句如何使用可以傳遞值到WHERE子句。

IbatisRead.java文件

這個文件的應用程序級的邏輯讀取雇員表中的記錄 -

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 IbatisRead{
   public static void main(String[] args)throws IOException,SQLException{
      Reader rd = Resources.getResourceAsReader("SqlMapConfig.xml");
      SqlMapClient smc = SqlMapClientBuilder.buildSqlMapClient(rd);

      /* This would read all records from the Employee table. */
      System.out.println("Going to read records.....");
      List <Employee> ems = (List<Employee>)
         smc.queryForList("Employee.getAll", null);
      Employee em = null;
		
      for (Employee e : ems) {
         System.out.print("  " + e.getId());
         System.out.print("  " + e.getFirstName());
         System.out.print("  " + e.getLastName());
         System.out.print("  " + e.getSalary());
         em = e; 
         System.out.println("");
      }    
		
      System.out.println("Records Read Successfully ");
   }
} 

編譯和運行

以下是編譯并運行上述軟件的步驟。請確保您已設置PATH和CLASSPATH在進行適當?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，并對其進行編譯。
• 創(chuàng)建IbatisRead.java如上圖所示，并對其進行編譯。
• 執(zhí)行IbatisRead二進制運行程序。

你會得到下面的結果，并創(chuàng)下會從EMPLOYEE表如下讀 -

Going to read records.....
   1  Zara  Ali  5000
Record Reads Successfully