DAO设计模式之禅[数据库万能查询操作]

package com.dao.bean;

/*
* 属性的封装类
* A class to do one thing
*/
public class Animals {
private int id;
private String name;
private int age;
private int anId;

public Animals(){

}

public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public int getAnId() {
return anId;
}
public void setAnId(int anId) {
this.anId = anId;
}

}

package com.jdbc.uitl;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
/*
*  DAO工具类
*  A class to do one thing
*
*/
public class JDBCUtil {
public static Connection open(){

Connection conn = null;

try {
//加载驱动
Class.forName("com.mysql.jdbc.Driver");
//获取连接数据库
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/animal","root","123456");

}catch (Exception e) {
System.out.println("数据库连接失败！");
}
return conn;
}

//关闭 2种 资源的方法
public static void closeRes(Connection conn ,PreparedStatement ps){
try {
if(ps!=null){
ps.close();
}
if(conn!=null){
conn.close();
}
} catch (Exception e) {
System.out.println("数据库资源已经关闭！");
}
}

//关闭 3种 资源的方法
public static void closeRes(Connection conn ,PreparedStatement ps,ResultSet rs){
try {
if(rs!=null){
rs.close();
}
if(ps!=null){
ps.close();
}
if(conn!=null){
conn.close();
}
} catch (Exception e) {
System.out.println("数据库资源已经关闭！");
}
}
}

package com.dao.data;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;
import com.jdbc.uitl.JDBCUtil;

/*
* 万能DAO
*
* */
public class DaoSelect {

//1、查询所有属性[返回一个集合、ArrayList]
@SuppressWarnings({ "rawtypes", "unchecked" })
public ArrayList getList(Class<?> cl){

ArrayList ar = new ArrayList();

Connection conn = JDBCUtil.open();
PreparedStatement ps = null;
ResultSet rs = null;

//获取类型名字、这里表示表名[对象.getSimpleName()]
String sql = "select *  from "+ cl.getSimpleName();
//获取属性[对象.getDeclaredFields()]
Field[] fi = cl.getDeclaredFields();

try {
//链接数据库
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();
Object ob = null;

while(rs.next()){

ob = cl.newInstance();

for(Field ff : fi){
//属性可见
ff.setAccessible(true);
ff.set(ob, rs.getObject(ff.getName()));
}
ar.add(ob);
}
} catch (Exception e) {
System.out.println("查询所以属性操作失败！");
}finally{
//关闭资源
JDBCUtil.closeRes(conn, ps, rs);
}
return ar;
}

//2、查询单个属性[返回一个属性、Object]
@SuppressWarnings("rawtypes")
public Object getObById(Class cl,int id){

Object ob = null;

Connection conn = JDBCUtil.open();
PreparedStatement ps = null;
ResultSet rs =null;

//获取属性[对象.getDeclaredFields()]
Field[] fi = cl.getDeclaredFields();
//获取属性名[对象.getSimpleName()]
String sql = "select * from "+cl.getSimpleName()+" where "+fi[0].getName()+" = "+id;

try {
//链接数据库
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();

while(rs.next()){

ob = cl.newInstance();

for(Field ff : fi){
ff.setAccessible(true);
ff.set(ob,rs.getObject(ff.getName()));
}
}
} catch (Exception e) {
System.out.println("查询单个属性操作失败！");
}finally{
JDBCUtil.closeRes(conn, ps, rs);
}
return ob;
}

//3、查询未知属性[返回一个集合、ArrayList]
@SuppressWarnings({ "rawtypes", "unchecked" })
public ArrayList getListBySome(Class cl ,String name,Object value){

ArrayList ar = new ArrayList();
Object ob = null;

Connection conn = JDBCUtil.open();
PreparedStatement ps = null;
ResultSet rs = null;

//获取属性、属性名[对象.getDeclaredFields()][对象.getSimpleName()]
Field[] fi = cl.getDeclaredFields();
String sql = "select * from "+cl.getSimpleName()+" where "+name+" = '"+value+"'";

try {
//连接数据库
ps = conn.prepareStatement(sql);
rs = ps.executeQuery();

while(rs.next()){

ob = cl.newInstance();

for(Field ff : fi){
ff.setAccessible(true);
ff.set(ob, rs.getObject(ff.getName()));
}
ar.add(ob);
}

} catch (Exception e) {
System.out.println("查询未知属性操作失败！");
}finally{
JDBCUtil.closeRes(conn, ps, rs);
}
return ar;

}
}

package com.dao.data;

import java.util.ArrayList;
import com.dao.bean.Animals;

/*
* 万能测试Class
*
*/
public class TestSelect {
@SuppressWarnings("unchecked")
public static void main(String[] args) {

DaoSelect dao = new DaoSelect();

//		//1、Animals类、所有属性
ArrayList<Animals> ar = dao.getList(Animals.class);
for (Animals an: ar) {
System.out.print("编号：" + an.getId() + "——名字：" + an.getName());
System.out.println("——年龄：" + an.getAge() + "——类型ID：" + an.getAnId());
}

//		//2、Animals类、查询单个属性
//		Animals ar1 = (Animals) dao.getObById(Animals.class, 2);
//		System.out.println("id为2的名字是：" + ar1.getName());

//3、Animals类、查询单个属性
//		ArrayList<Animals> ar1 = dao.getListBySome(Animals.class, "name", "陈郑游");
//
//		ArrayList<Animals> ar = dao.getListBySome(Animals.class, "age", "21");
//		for (Animals an: ar ) {
//			System.out.println("编号：" + an.getId() + "——名字：" + an.getName());
//		}
}

}

//动物类数据库

create database animals ;
use  animals;

create table  animals
(	id int primary key,
name varchar(20) ,
sex char(2),
age int ,
anid int
);