我们在上一章讨论了如何使用iBATIS对表执行CREATE操作.本章介绍如何使用iBATIS读取表格.
我们在MySQL中有以下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));
此表只有一条记录如下 :
mysql> select * from EMPLOYEE;+----+------------+-----------+--------+| id | first_name | last_name | salary |+----+------------+-----------+--------+| 1 | Zara | Ali | 5000 |+----+------------+-----------+--------+1 row in set (0.00 sec)
员工POJO类
要执行读取操作,我们将修改Employee类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
要使用iBATIS定义SQL映射语句,我们将添加< select>在Employee.xml文件中标记并在此标记定义中,我们将定义一个"id",它将在IbatisRead.java文件中用于在数据库上执行SQL SELECT查询.
<?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>
这里我们没有将WHERE子句与SQL SELECT语句一起使用.我们将在下一章中演示如何在SELECT语句中使用WHERE子句以及如何将值传递给该WHERE子句.
IbatisRead.java文件
此文件具有应用程序级逻辑,用于从Employee表读取记录 :
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 "); } }
编译并运行
以下是编译和运行的步骤上面提到的软件.在继续进行编译和执行之前,请确保已正确设置PATH和CLASSPATH.
如上所示创建Employee.xml.
如上所示创建Employee.java并进行编译.
如上所示创建IbatisRead.java并编译它.
执行IbatisRead二进制文件以运行程序.
您将得到以下结果,并且将从EMPLOYEE表中读取记录,如下所示;
Going to read records..... 1 Zara Ali 5000Record Reads Successfully
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