resultMap的元素是在MyBatis的最重要和最强大的元素。您可以通过使用MyBatis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。
创建Employee.xml如上所示。
创建Employee.java如上图所示，并编译它。
创建IbatisResultMap.java如上图所示，并编译它。
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
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