仿照Hibernate实现的ORMapping简单映射

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

import com.zjh.hibernate.model.Student; //自己定义的Student类，包含int id,String name,int age 这三个成员变量


public class Session {
	String tableName;
	Map<String, String> cfs = new HashMap<String, String>(); //cfs意思是configurations
	
	String[] methodNames;
	
	public Session() {
		cfs.put("_id", "id");
		cfs.put("_name", "name");
		cfs.put("_age", "age"); 
		tableName = "_student"; //这里默认已经读到配置文件，得到了映射关系
		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","root");
		PreparedStatement ps = conn.prepareStatement(sql);
		
		for(int i=0;i<methodNames.length;i++) {
			String mName = methodNames[i];
			Method m = s.getClass().getMethod(mName);
			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")) {
				int returnValue = (Integer)m.invoke(s);
				ps.setInt(i+1, returnValue);
			}
		}
	
		ps.executeUpdate();
		ps.close();
		conn.close();
	}

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

自己实现的Hibernate insert语句自动生成的方法。假设已经从配置文件中读到映射关系，并且数据库中存在名为"_student"的表。