利用反射完成初级万能DAO

一、目标

利用反射完成初级万能DAO

二、注意

1.Field[] fi = clazz.getDeclaredFields();　

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

三、代码

package com.jikexueyuan.util;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.util.ArrayList;

import com.jikexueyuan.bean.AnType;
import com.jikexueyuan.bean.Animals;


public class BaseDAO {
	public ArrayList getList(Class cl){
		ArrayList ar = new ArrayList();
		Connection conn = BaseConnection.getConnection();
		PreparedStatement ps = null;
		ResultSet rs = null;
		String sql = "select *  from "+cl.getSimpleName();
		Field[] fi = cl.getDeclaredFields();
		try {
			ps = conn.prepareStatement(sql);
			rs = ps.executeQuery();
			while(rs.next()){
				Object ob = cl.newInstance();//ʵÀý»¯Àà¶ÔÏó
				for(Field ff : fi){
					ff.setAccessible(true);
					ff.set(ob, rs.getObject(ff.getName()));
				}
				ar.add(ob);
				
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			BaseConnection.closeRes(conn, ps, rs);
		}

		return ar;
	}
	public Object getObById(Class cl,int id){
		Object ob = null;
		Connection conn = BaseConnection.getConnection();
		PreparedStatement ps = null;
		ResultSet rs =null;
		Field[] fi = cl.getDeclaredFields();
		String sql = "select * from "+cl.getSimpleName()+" where "+fi[0].getName()+" = "+id;
		try {
			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) {
			e.printStackTrace();
		}finally{
			BaseConnection.closeRes(conn, ps, rs);
		}
		return ob;
	}
	public ArrayList getListBySome(Class cl ,String name,Object value){
		ArrayList ar = new ArrayList();
		Connection conn = BaseConnection.getConnection();
		PreparedStatement ps = null;
		ResultSet rs = null;
		Field[] fi = cl.getDeclaredFields();
		String sql = "select * from "+cl.getSimpleName()+" where "+name+" = '"+value+"'";
		try {
			ps = conn.prepareStatement(sql);
			rs = ps.executeQuery();
			while(rs.next()){
				Object ob = cl.newInstance();
				for(Field ff : fi){
					ff.setAccessible(true);
					ff.set(ob, rs.getObject(ff.getName()));
				}
				ar.add(ob);
			}
			
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			BaseConnection.closeRes(conn, ps, rs);
		}
		return ar;
	
	}
	public boolean insert(Object ob){
		boolean b = false;
		Connection conn = BaseConnection.getConnection();
		PreparedStatement ps = null;
		Class cl = ob.getClass();
		Field[] fi = cl.getDeclaredFields();
		//insert into animals (name,age,anid) values(?,?,?)
		String sql = "insert into "+cl.getSimpleName()+" (";
		for(int i = 1;i<fi.length;i++){
			sql = sql+fi[i].getName();
			//4  0 1 2 3
			if(i!=fi.length-1){
				sql = sql+" , ";
			}
		}
		sql = sql+") values (";
		for(int i = 1;i<fi.length;i++){
			sql = sql+" ? ";
			if(i!=fi.length-1){
				sql = sql+" , ";
			}
		}
		sql = sql+")";
		try {
			ps = conn.prepareStatement(sql);
			for(int i = 1;i<fi.length;i++){
				fi[i].setAccessible(true);
				ps.setObject(i, fi[i].get(ob));
			}
			int a = ps.executeUpdate();
			if(a>0){
				b = true;
			}
			
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			BaseConnection.closeRes(conn, ps);
		}
		return b;
	}
	public boolean insert1(Object ob){
		boolean b = false;
		Connection conn = BaseConnection.getConnection();
		PreparedStatement ps = null;
		Class cl = ob.getClass();
		Field[] fi = cl.getDeclaredFields();
		StringBuffer sb = new StringBuffer();
		//insert into animals (name,age,anid) values(?,?,?)
		sb.append("insert into ");
		sb.append(cl.getSimpleName());
		sb.append(" (");
		for(int i = 1;i<fi.length;i++){
			sb.append(fi[i].getName());
			if(i!=fi.length-1){
				sb.append(" , ");
			}
		}
		sb.append(") values (");
		for(int i = 1;i<fi.length;i++){
			sb.append(" ? ");
			if(i!=fi.length-1){
				sb.append(" , ");
			}
		}
		sb.append(" ) ");
		try {
			ps = conn.prepareStatement(sb.toString());
			for(int i = 1;i<fi.length;i++){
				fi[i].setAccessible(true);
				ps.setObject(i, fi[i].get(ob));
			}
			int a = ps.executeUpdate();
			if(a>0){
				b = true;
			}
			
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			BaseConnection.closeRes(conn, ps);
		}
		return b;
	}
	
	public boolean update(Object ob){
		boolean b = false;
		Connection conn = BaseConnection.getConnection();
		PreparedStatement ps = null;
		Class cl = ob.getClass();
		Field[] fi = cl.getDeclaredFields();
		StringBuffer sb = new StringBuffer();
		//update animals set name = ?,age = ?,anid = ? where id = ?
		sb.append(" update ");
		sb.append(cl.getSimpleName());
		sb.append(" set ");
		for(int i = 1;i<fi.length;i++){
			fi[i].setAccessible(true);
			sb.append(fi[i].getName());
			sb.append(" = ? ");
			if(i!=fi.length-1){
				sb.append(" , ");
			}
		}
		sb.append(" where ");
		sb.append(fi[0].getName());
		sb.append("=?");
		
		try {
			ps = conn.prepareStatement(sb.toString());
			for(int i = 1;i<fi.length;i++){
				fi[i].setAccessible(true);
				ps.setObject(i, fi[i].get(ob));
			}
			fi[0].setAccessible(true);
			ps.setObject(fi.length, fi[0].get(ob));
			int a = ps.executeUpdate();
			if(a>0){
				b = true;
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			BaseConnection.closeRes(conn, ps);
		}
		return b;
	}
	
	public boolean delete(Class cl , int id){
		boolean b = false;
		Connection conn = BaseConnection.getConnection();
		PreparedStatement ps = null;
		Field[] fi = cl.getDeclaredFields();
		String sql = "delete from "+cl.getSimpleName()+" where "+fi[0].getName()+" = ?";
		try {
			ps = conn.prepareStatement(sql);
			ps.setObject(1, id);
			int a = ps.executeUpdate();
			if(a>0){
				b = true;
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			BaseConnection.closeRes(conn, ps);
		}
	return b ;
	
	}
	public boolean deleteBySome(Class cl , String name,Object value){
		boolean b = false;
		Connection conn = BaseConnection.getConnection();
		PreparedStatement ps = null;
		Field[] fi = cl.getDeclaredFields();
		String sql = "delete from "+cl.getSimpleName()+" where "+name+" = ?";
		try {
			ps = conn.prepareStatement(sql);
			ps.setObject(1, value);
			int a = ps.executeUpdate();
			if(a>0){
				b = true;
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally{
			BaseConnection.closeRes(conn, ps);
		}
	return b ;
	
	}
	public static void main(String[] args) {
		BaseDAO bd = new BaseDAO();
//		Animals an = new Animals();
//		an.setName("½ð¾ÅÅÖ");
//		an.setAge(15);
//		an.setAnId(1);
//		an.setId(3);
//		boolean b = bd.update(an);
		
		bd.deleteBySome(Animals.class, "name","½ð¾ÅÅÖ");
		//bd.delete(Animals.class, 5);
//		ArrayList<Animals> ar = bd.getList(Animals.class);
//		for(Animals an : ar){
//			System.out.println("±àºÅ£º"+an.getId()+"Ãû×Ö£º"+an.getName()+"ÄêÁä:"+an.getAge());
//		}
//		ArrayList<AnType> arr = bd.getList(AnType.class);
//		for(AnType an : arr){
//			System.out.println("±àºÅ£º"+an.getAnId()+"Ãû×Ö£º"+an.getAnName());
//		}
//		Animals an = (Animals)bd.getObById(Animals.class, 2);
//		System.out.println(an.getName());
//		ArrayList<Animals> ar = bd.getListBySome(Animals.class, "age", "13");
//		for(Animals an : ar){
//			System.out.println("±àºÅ£º"+an.getId()+"Ãû×Ö£º"+an.getName()+"ÄêÁä:"+an.getAge());
//		}
	}
}

　　源代码：https://files.cnblogs.com/files/shamgod/Java-DAO-4-v2.7z

转自jikexueyuan