将jdbc结果集转换成对象列表

将jdbc结果集转换成对象列表
估计hibernate就是用得这种方式进行转换的。
实体对象

package test;
//实体对象，该对象的属性与数据库中的字段相同，当然可以改变具体看需求
public class Person {
	private int id;
	private int age;
	private String name;
	public int getId() {
		return id;
	}
	public void setId(int id) {
		this.id = id;
	}
	public int getAge() {
		return age;
	}
	public void setAge(int age) {
		this.age = age;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	
}

package test;

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

public class Main {
	//用于测试的方法
	public static void main(String[] args) throws InstantiationException, IllegalAccessException, IllegalArgumentException, ClassNotFoundException {
		Connection conn = DbUtils.getConn();
		ResultSet rs = null;
		PreparedStatement psmt = null;
		System.out.println(conn);
		try {
			psmt = conn.prepareStatement("select * from person");
			rs = psmt.executeQuery();
			List list = DbUtils.populate(rs, Person.class);
			for(int i = 0 ; i<list.size() ; i++){
				Person per = (Person) list.get(i);
				System.out.println("person : id = "+per.getId()+" name = "+per.getName()+" age = "+per.getAge());
			}
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			if(rs!=null){
				try {
					rs.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
				rs=null;
			}
			if(psmt!=null){
				try {
					psmt.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
				psmt=null;
			}
			if(conn!=null){
				try {
					conn.close();
				} catch (SQLException e) {
					e.printStackTrace();
				}
				conn=null;
			}
		}
		
	}

}

具体的工具类

package test;

import java.lang.reflect.Field;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class DbUtils {
	private static String url = "jdbc:mysql://localhost:3306/test";
	private static String username = "root";
	private static String password = "";
	private static String driverClass = "com.mysql.jdbc.Driver";
	//没什么好说的，获取数据库连接
	public static Connection getConn(){
		Connection conn = null;
		try {
			Class.forName(driverClass);
			conn = DriverManager.getConnection(url,username,password);
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		
		return conn;
	}
	/*
	 * 将rs结果转换成对象列表
	 * @param rs jdbc结果集
	 * @param clazz 对象的映射类
	 * return 封装了对象的结果列表
	 */
	public static List populate(ResultSet rs , Class clazz) throws SQLException, InstantiationException, IllegalAccessException{
		//结果集的元素对象 
		ResultSetMetaData rsmd = rs.getMetaData();
		//获取结果集的元素个数
		 int colCount = rsmd.getColumnCount();
//		 System.out.println("#");
//		 for(int i = 1;i<=colCount;i++){
//			 System.out.println(rsmd.getColumnName(i));
//			 System.out.println(rsmd.getColumnClassName(i));
//			 System.out.println("#");
//		 }
		 //返回结果的列表集合
		 List list = new ArrayList();
		 //业务对象的属性数组
		 Field[] fields = clazz.getDeclaredFields();
		 while(rs.next()){//对每一条记录进行操作
			 Object obj = clazz.newInstance();//构造业务对象实体
			 //将每一个字段取出进行赋值
			 for(int i = 1;i<=colCount;i++){
				 Object value = rs.getObject(i);
				 //寻找该列对应的对象属性
				 for(int j=0;j<fields.length;j++){
					 Field f = fields[j];
					 //如果匹配进行赋值
					 if(f.getName().equalsIgnoreCase(rsmd.getColumnName(i))){
						 boolean flag = f.isAccessible();
						 f.setAccessible(true);
						 f.set(obj, value);
						 f.setAccessible(flag);
					 }
				 }
			 }
			 list.add(obj);
		 }
		return list;
	}
}

评论

1 楼 u010778233 2016-08-26  

写得很不错，已经用起来了，谢谢