ORM的demo实现

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.bjsxt.hibernate.model.Student;

public class Session {
    String tableName = "_Student";
    Map<String, String> cfs = new HashMap<String, String>();
    String[] methodNames;// 用于存入实体类中的get方法数组

    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();// 创建SQL串
        
        Class.forName("com.mysql.jdbc.Driver");
        Connection conn = DriverManager.getConnection(
                "jdbc:mysql://xxx:3306/xxx?characterEncoding=UTF-8&zeroDateTimeBehavior=convertToNull", "xxx",
                "xxx");
        PreparedStatement ps = conn.prepareStatement(sql);
        for (int i = 0; i < methodNames.length; i++) {
            Method m = s.getClass().getMethod(methodNames[i]);// 返回一个 Method
                                                                // 对象，它反映此 Class
                                                                // 对象所表示的类或接口的指定公共成员方法
            Class r = m.getReturnType();// 返回一个 Class 对象，该对象描述了此 Method
                                        // 对象所表示的方法的正式返回类型
            if (r.getName().equals("java.lang.String")) {
                // 对带有指定参数的指定对象调用由此 Method 对象表示的底层方法。
                // 个别参数被自动解包，以便与基本形参相匹配，基本参数和引用参数都随需服从方法调用转换
                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);
            }
            if (r.getName().equals("java.lang.String")) {
                String returnValue = (String) m.invoke(s);
                ps.setString(i + 1, returnValue);
            }
            System.out.println(m.getName() + "|" + r.getName());
        }
        ps.executeUpdate();
        ps.close();
        conn.close();
    }

    private String createSQL() {
        String str1 = "";
        int index = 0;
        for (String s : cfs.keySet()) {
            String v = cfs.get(s);// 取出实体类成员属性
            v = Character.toUpperCase(v.charAt(0)) + v.substring(1);// 将成员属性第一个字符大写
            methodNames[index] = "get" + v;// 拼实体类成员属性的getter方法
            str1 += s + ",";// 根据表中字段名拼成字段串
            index++;
        }
        str1 = str1.substring(0, str1.length() - 1);
        String str2 = "";
        // 根据表中字段数，拼成?串
        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;
    }
}

package com.bjsxt.hibernate.model;

public class Student {
    private int id;
    private String name;
    private int age;
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
}

import com.bjsxt.hibernate.model.Student;


public class StudentTest {
    public static void main(String[] args) throws Exception {
        Student s = new Student();
        s.setName("xx");
        s.setAge(2);
        s.setId(2);
        
        Session session = new Session();
        
        session.save(s);
        
    }
}