模拟Hibernate框架的小demo

该程序为尚学堂马士兵老师讲解，模拟了hibernate的原理，主要应用了字符串拼接，反射知识。

step1,新建数据库

  

use jd;

create table _student(

_id int(11),

_nage varchar(20),

_age int(11));

step 2 student实体类，再次略过

 

step3,编写session类，模拟hibernate的实现原理。

 

import java.lang.reflect.InvocationTargetException;

import java.lang.reflect.Method;

import java.sql.Connection;

import java.sql.DriverManager;

import java.sql.PreparedStatement;

import java.sql.SQLException;

import java.util.HashMap;

import java.util.Map;



import com.bjsxt.hibernate.model.Student;



public class Session {

	static String tableName = "_Student";

	static Map<String, String> cfs = new HashMap<String, String>();

	static String[] methodNames;



	public Session() {

		cfs.put("_id", "id");

		cfs.put("_name", "name");

		cfs.put("_age", "age");

		methodNames = new String[cfs.size()];

	}



	public static void save(Student s) throws Exception {

		// TODO Auto-generated method stub

		int index = 0;

		String sql = createSql();



		try {

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

			Connection conn = DriverManager.getConnection(

					"jdbc:mysql://localhost/jd", "root", "123456");

			PreparedStatement ps = conn.prepareStatement(sql);

				



			for (int i = 0; i < methodNames.length; i++) {

				Method m = s.getClass().getMethod(methodNames[i]);

				Class r = m.getReturnType();

				if (r.getName().equals("java.lang.String")) {

					String returnValue = (String) m.invoke(s);

					ps.setString(i + 1, returnValue);

					System.out.println(returnValue);

				}

				if (r.getName().equals("int")) {

					Integer returnValue = (Integer) m.invoke(s);

					ps.setInt(i + 1, returnValue);

					System.out.println(returnValue);

				}

				// System.out.println(m.getName()+","+m.getReturnType()+","+r.getName());

			}

			System.out.println(sql);

			ps.executeUpdate();	

			ps.close();

			conn.close();

		} catch (Exception e) {

			// TODO Auto-generated catch block

			e.printStackTrace();

		}



	}



	private static String createSql() {



		String str2 = "";

		String str1 = "";

		int index = 0;

		for (String s : cfs.keySet()) {//s为_id,_Age,_Name

			String v = cfs.get(s);

			v = Character.toUpperCase(v.charAt(0)) + v.substring(1);//Id,Name,Age

			//System.out.println(v+"涛");

			methodNames[index] = "get" + v; // str1+=s+",";//getId,getName,getAge

			//System.out.println(s);

			//System.out.println(methodNames[index]);

			str1 += s + ",";

			index++;

			System.out.println(str1);

		}

		str1 = str1.substring(0, str1.length() - 1);

		//System.out.println(str1);

		for (int i = 0; i < cfs.size(); i++) {



			if (i == cfs.size() - 1) {

				str2 += "?";

			} else {

				str2 += "?,";

			}



		}

		//System.out.println(str2);

		String sql = "insert into " + tableName + "(" + str1 + ")"

				+ " values (" + str2 + ")";

		System.out.println(sql+"createSql方法里面");

		return sql;

	}



}

step4，测试，

import com.bjsxt.hibernate.model.Student;

public class StudentTest {



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



		Student s = new Student();

		s.setId(10);

		s.setName("s1");

		s.setAge(1);		

		Session session = new Session();

		session.save(s);

	}

}