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iBATIS读取操作

上一章展示了如何使用iBATIS执行创建操作表。本章将告诉你如何使用iBATIS来读取表。

我们已经在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) );

此表有如下只有一条记录:

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

Employee POJO 类:

要执行读操作,我们将修改Employee类中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:

要定义使用iBATIS SQL映射语句,我们将增加

在这里,我们没有使用WHERE子句和SQL SELECT语句。后续章节将演示如何用WHERE和SELECT语句子句,以及如何将值传递到WHERE子句。

IbatisRead.java 文件:

该文件将应用程序级别的逻辑从雇员Employee表中读出记录:

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 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 "); } } 

编译和运行:

下面是步骤来编译并运行上述应用。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如上图所示,并编译它。

  • 创建IbatisRead.java如上图所示,并编译它。

  • 执行IbatisRead二进制文件来运行程序。

你会得到下面的结果,并且将记录从EMPLOYEE表中读取。

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