hibernate模拟

最新推荐文章于 2018-07-31 12:28:27 发布

原创最新推荐文章于 2018-07-31 12:28:27 发布 · 943 阅读

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本文通过一个简单的例子展示了如何使用反射机制来模拟Hibernate的SQL封装过程。该实例创建了一个Student类并利用反射动态生成SQL语句，进而实现数据的保存操作。

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模拟hibernate的sql封装，主要为了讲解反射的运用

package com.hibernate.model;

public class Student {
	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;
	}
	
	
}

import com.hibernate.model.Student;


public class StudentTest {
	public static void main(String[] args) throws Exception {
		Student s = new Student();
		s.setId(1);
		s.setName("s1");
		s.setAge(1);
		
		Session session = new Session();
		session.save(s);
	}
}

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

import com.hibernate.model.Student;





public class Session {
	String tableName = "_Student";
	Map<String, String> cfs = new HashMap<String, String>();
	
	String[] methodNames = null;

	public Session() {
		cfs.put("_id", "id");
		cfs.put("_name", "name");
		cfs.put("_age", "age");
		methodNames = new String[cfs.size()];
	}
	
	public void save(Student s) throws Exception {					
		String sql = createSQL();
		
		Class.forName("com.mysql.jdbc.Driver");
		Connection conn = DriverManager.getConnection("jdbc:mysql://localhost/hibernate","root","gonglishan520");
		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);
			}
			if(r.getName().equals("int")){
				Integer returnValue = (Integer)m.invoke(s);
				ps.setInt(i+1, returnValue);
			}
			
		}
		ps.executeUpdate();
		ps.close();
	}

	private String createSQL() {
		String str1 = "";
		int index = 0;
		for(String s: cfs.keySet()){
			String v = cfs.get(s);
			v = Character.toUpperCase(v.charAt(0)) + v.substring(1,v.length());
			methodNames[index] = "get"+ v;
			str1 += s + ",";
			index++;
		}
		
		str1 = str1.substring(0,str1.length()-1);
		
		String str2 = "";

		for(int i=0; i<cfs.size(); i++){
			str2 += "?,";
		}
		
		str2 = str2.substring(0,str2.length()-1);
		String sql = "insert into "+tableName+"("+str1+") " +"values("+str2+")" ;
		System.out.println(sql);
		return sql;
	}

}