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)
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 */
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
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 "); } }
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
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