hibernate模拟（转载）

package simulation;
/**
 *
 * @author Administrator
 *
 */
public class User {
    private int id;
    private String username;
    private String pwd;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public String getPwd() {
        return pwd;
    }
    public void setPwd(String pwd) {
        this.pwd = pwd;
    }

}

package simulation;

import java.lang.reflect.Method;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

import com.mysql.jdbc.PreparedStatement;

public class Session {

    private String table="user";
    private Map<String, String> params=new HashMap<String, String>();
    //装入方法名的容器
    String [] methodName;

    public Session() {
        //模拟配置文件 key为属性 value为数据列
        params.put("id", "_id");
        params.put("pwd", "_pwd");
        params.put("username", "_username");
        methodName=new String[params.size()];
    }

    public void save(User user){

        String sql = creatSQL();
        System.out.println(sql);
        //数据库操作
        try {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/hibernate","root","123456");
            PreparedStatement state =  (PreparedStatement) con.prepareStatement(sql);
            //为占位符设值
            for (int i = 0; i < methodName.length; i++) {
                //反射取值
                Method method = user.getClass().getMethod(methodName[i]);
                Class<?> clazz = method.getReturnType();
                if (clazz.getName().equals("java.lang.String")) {
                    state.setString(i+1, (String) method.invoke(user));
                }
                if (clazz.getName().equals("int")) {
                    state.setInt(i+1, (Integer) method.invoke(user));
                }
                System.out.println(method.getName()+":"+method.getReturnType());
            }
            state.executeUpdate();
            state.close();
            con.close();
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

    }

    public  String creatSQL() {
        String parameters="";
        String values="";
        int index=0;
        //拼接属性字符串和值字符串
        for (String  key: params.keySet()) {
//            System.out.println(key);
            parameters+=params.get(key)+",";
            String v="get"+Character.toUpperCase(key.charAt(0))+key.substring(1);
//            System.out.println(methodName.length);
            methodName[index]=v;
            index++;
        }
        parameters=parameters.substring(0,parameters.length()-1);
        System.out.println(Arrays.toString(methodName));
        for (int i = 0; i < params.size(); i++) {
            values+="?,";
        }
        values=values.substring(0,values.length()-1);
        String sql="insert into "+table+"("+parameters+") values ("+values+")";
        return sql;
    }

}

package simulation;

public class HibernateTest {

    public static void main(String[] args) {

        User user=new User();
        user.setId(1);
        user.setPwd("123456");
        user.setUsername("a");
        Session session=new Session();
        session.save(user);

    }

}