最簡單的ORM

1.準備資料庫

drop database if exists orm_test;

create database if not exists orm_test character set gbk;

use orm_test;

create table person_table

(

    id int auto_increment primary key,

    name varchar(255) not null,

    age int,

    height int,

    weight float

);

insert into person_table values(null, 'zhangsan', 21, 175, 60);

insert into person_table values(null, 'lisi', 30, 180, 70);

insert into person_table values(null, 'wangwu', 21, 178, 59);

insert into person_table values(null, 'leeyohn', 21, 176, 60);

insert into person_table values(null, 'yun', 22, 168, 50);

insert into person_table values(null, 'zhaoliu', 21, 170, 80);

insert into person_table values(null, 'king', 25, 168, 68);

2.編寫實體類

public class Person

{

private int id;

private String name;

private int age;

private int height;

private float weight;

//無參數構造器

public Person()

{

}

//初始化全部屬性的構造器

public Person(int id, String name, int age, int height

, float weight)

{

this.id = id;

this.name = name;

this.age = age;

this.height = height;

this.weight = weight;

}

//id屬性的setter和getter方法

public void setId(int id)

{

this.id = id;

}

public int getId()

{

return id;

}

//name屬性的setter和getter方法

public void setName(String name)

{

this.name = name;

}

public String getName()

{

return name;

}

//age屬性的setter和getter方法

public void setAge(int age)

{

this.age = age;

}

public int getAge()

{

return age;

}

//height屬性的setter和getter方法

public void setHeight(int height)

{

this.height = height;

}

public int getHeight()

{

return height;

}

//weight屬性的setter和getter方法

public void setWeight(float weight)

{

this.weight = weight;

}

public float getWeight()

{

return weight;

}

public String toString()

{

return "name=" + name + " age=" + age

+ " height=" + height + " weight=" + weight;

}

}

SimpleORM.java

import java.lang.reflect.*;

import java.sql.*;

/*

* Copyright 2009-2012 the original author or authors.

* Description:

* <br/>網站: <a href="http://www.crazyit.org" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" mce_href="http://www.crazyit.org" target="_blank" rel="external nofollow" target="_blank" rel="external nofollow" >瘋狂Java聯盟</a>

* <br/>Program Name: SimpleORM.java

* <br/>Project Name:

* <br/>Date: 2010-2-11

* @author : leeyohn

* @e-mail : [email protected]

* @QQ : 1417515725

* @version : 1.0

*/

public class SimpleORM

{

private Connection conn;

private PreparedStatement pstmt;

private ResultSet rs;

private void getConnection() throws Exception

{

if (conn == null)

{

Class.forName("com.mysql.jdbc.Driver");

conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/orm_test", "root", "12345");

}

}

public Object get(String table, int id, Class<?> clazz) throws Exception

{

getConnection();

pstmt = conn.prepareStatement("select * from " + table + " where id=?");

pstmt.setInt(1, id);

ResultSet rs = pstmt.executeQuery();

if (rs.next())

{

Object target = clazz.newInstance();

Method[] methods = clazz.getDeclaredMethods();

//擷取結果集中繼資料

ResultSetMetaData meta = pstmt.getMetaData();

//擷取表中列數

int cols = meta.getColumnCount();

for (int i = 0; i < cols; i++)

{

String colName = meta.getColumnName(i + 1);

for (int j = 0; j < methods.length; j++)

{

//是否比對setter方法

if (methods[j].getName().equalsIgnoreCase("set" + colName))

{

methods[j].invoke(target, rs.getObject(i + 1));

}

}

}

return target;

}

return null;

}

public void closeRs() throws Exception

{

if (rs != null)

{

rs.close();

}

if (pstmt != null)

{

pstmt.close();

}

if (conn != null)

{

conn.close();

}

}

public static void main(String[] args) throws Exception

{

SimpleORM orm = new SimpleORM();

Person p = (Person)orm.get("person_table", 1, Person.class);

System.out.println(p);

orm.closeRs();

}

}