iBATIS - Result Maps
resultMap元素是iBATIS中最重要和最强大的元素。 您可以使用iBATIS ResultMap减少高达90％的JDBC编码，在某些情况下，它允许您执行JDBC甚至不支持的操作。
ResultMaps的设计使得简单语句根本不需要显式结果映射，而更复杂的语句只需要描述关系的绝对必要。
本章仅提供iBATIS ResultMaps的简单介绍。
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)
);
该表有两条记录如下 -
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 Class
要使用iBATIS ResultMap，您无需修改Employee.java文件。 让我们保持原样在最后一章。
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 File
在这里，我们将修改Employee.xml以引入
<?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 File
此文件具有应用程序级逻辑，可使用ResultMap从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 (Compilation and Run)
以下是编译和运行上述软件的步骤。 在继续编译和执行之前，请确保已正确设置PATH和CLASSPATH。
- 创建Employee.xml，如上所示。
- 如上所示创建Employee.java并编译它。
- 如上所示创建IbatisResultMap.java并进行编译。
- 执行IbatisResultMap二进制文件来运行程序。
您将获得以下结果，这是EMPLOYEE表上的读取操作。
Going to read record.....
ID: 1
First Name: Zara
Last Name: Ali
Salary: 5000
Record read Successfully
