MyBatis知多少(20)MyBatis讀取操做

上篇展現瞭如何使用MyBatis執行建立操做表。本章將告訴你如何使用MyBatis來讀取表。html

咱們已經在MySQL下有EMPLOYEE表:java

1 CREATE TABLE EMPLOYEE (
2    id INT NOT NULL auto_increment,
3    first_name VARCHAR(20) default NULL,
4    last_name  VARCHAR(20) default NULL,
5    salary     INT  default NULL,
6    PRIMARY KEY (id)
7 );

 

此表有以下只有一條記錄:mysql

1 mysql> select * from EMPLOYEE;
2 +----+------------+-----------+--------+
3 | id | first_name | last_name | salary |
4 +----+------------+-----------+--------+
5 |  1 | Zara       | Ali       |   5000 |
6 +----+------------+-----------+--------+
7 1 row in set (0.00 sec)

 

Employee POJO 類:

要執行讀操做,咱們將修改Employee類中Employee.java文件,以下所示:sql

 1 public class Employee {
 2   private int id;
 3   private String first_name; 
 4   private String last_name;   
 5   private int salary;  
 6 
 7   /* Define constructors for the Employee class. */
 8   public Employee() {}
 9   
10   public Employee(String fname, String lname, int salary) {
11     this.first_name = fname;
12     this.last_name = lname;
13     this.salary = salary;
14   }
15 
16   /* Here are the method definitions */
17   public int getId() {
18     return id;
19   }
20   public String getFirstName() {
21     return first_name;
22   }
23   public String getLastName() {
24     return last_name;
25   }
26   public int getSalary() {
27     return salary;
28   }
29 } /* End of Employee */

 

Employee.xml 文件:

要定義使用iBATIS SQL映射語句,咱們將增長<select>標記在Employee.xml文件,這個標籤訂義中,咱們會定義將用於在IbatisRead.java文件的數據庫執行SQL SELECT查詢的「id」。數據庫

<?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>

 

在這裏,咱們沒有使用WHERE子句和SQL SELECT語句。後續章節將演示如何用WHERE和SELECT語句子句,以及如何將值傳遞到WHERE子句。apache

IbatisRead.java 文件:

該文件將應用程序級別的邏輯從僱員Employee表中讀出記錄:ui

 
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 ");

  }
}

 

編譯和運行:

下面是步驟來編譯並運行上述應用。請確保您已在進行的編譯和執行以前,適當地設置PATH和CLASSPATH。this

  • 建立Employee.xml如上所示。spa

  • 建立Employee.java如上圖所示,並編譯它。code

  • 建立IbatisRead.java如上圖所示,並編譯它。

  • 執行IbatisRead二進制文件來運行程序。

你會獲得下面的結果,而且將記錄從EMPLOYEE表中讀取。

1 Going to read records.....
2   1  Zara  Ali  5000
3 Record Reads Successfully

系列文章:

MyBatis知多少(1)

MyBatis知多少(2)

MyBatis知多少(3)

MyBatis知多少(4)MyBatis的優點

MyBatis知多少(5)業務對象模型

MyBatis知多少(6)表現層與業務邏輯層

MyBatis知多少(7)持久層

MyBatis知多少(8)關係型數據庫

MyBatis知多少(9)不一樣類型的數據庫

MyBatis知多少(10)應用程序數據庫

MyBatis知多少(11)企業數據庫

MyBatis知多少(12)私有數據庫

MyBatis知多少(13)MyBatis如何解決數據庫的常見問題

MyBatis知多少(14)分散的數據庫系統

MyBatis知多少(15)數據模型

MyBatis知多少(16)MyBatis映射

MyBatis知多少(17)MyBatis和JDBC

MyBatis知多少(18)MyBatis系統

MyBatis知多少(19)MyBatis操做

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