iBATIS结果映射
resultMap的元素是在iBATIS的最重要和最强大的元素。您可以通过使用iBATIS的结果映射减少高达90％的JDBC编码，在某些情况下，可以让你做JDBC不支持的事情。
ResultMaps的设计是这样的简单语句不需要明确的结果映射，以及更复杂的报表要求不超过绝对必要说明的关系。
本章将只给你一个简单的介绍iBATIS的结果映射。
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) );
此表有如下两条记录：
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 类:
使用iBATIS的结果映射，需要修改Employee.java文件。因此，让我们保持它，因为它已经在前一章中使用过。
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:
在这里，我们将修改Employee.xml文件介绍<resultMap></ resultMap>标记。这个标签就必须在我们<select>标记的resultMap属性运行此结果映射这是需要一个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:
文件将应用程序级别的逻辑，从使用结果映射Employee表中读取记录：
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 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 "); } }
编译和运行：
下面是步骤来编译并运行上述软件。请确保您已在进行的编译和执行之前，适当地设置PATH和CLASSPATH。
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创建Employee.xml如上所示。
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创建Employee.java如上图所示，并编译它。
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创建IbatisResultMap.java如上图所示，并编译它。
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执行IbatisResultMap二进制文件来运行程序。
会得到下面的结果是对EMPLOYEE表的读操作。
Going to read record..... ID: 1 First Name: Zara Last Name: Ali Salary: 5000 Record read Successfully
正文到此结束
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