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。

  • 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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