iBATIS讀取操作

上一章展示瞭如何使用iBATIS執行創建操作表。本章將告訴你如何使用iBATIS來讀取表。

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) );

此表有如下只有一條記錄：

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

Employee POJO 類:

要執行讀操作，我們將修改Employee類中Employee.java文件，如下所示：

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，我們將增加標記在Employee.xml文件，這個標籤定義中，我們會定義將用於在IbatisRead.java文件的數據庫執行SQL SELECT查詢的「id」。

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

在這裏，我們沒有使用WHERE子句和SQL SELECT語句。後續章節將演示如何用WHERE和SELECT語句子句，以及如何將值傳遞到WHERE子句。

IbatisRead.java 文件:

該文件將應用程序級別的邏輯從僱員Employee表中讀出記錄：

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：

下面是步驟來編譯並運行上述應用。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IbatisRead.java如上圖所示，並編譯它。

• 執行IbatisRead二進制文件來運行程序。

你會得到下面的結果，並且將記錄從EMPLOYEE表中讀取。

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