Hibernate之原理淺析

first model：

student.java:

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;
	}
	
	
}

then 原理模擬：

Session.java:

public class Session {
	
	String tableName = "_Student";
	Map<String,String> cfs = new HashMap<String ,String>();
	
	String [] methodNames = new String[cfs.size()];
	
	public Session(){
		cfs.put("_id", "id");
		cfs.put("_name", "name");
		cfs.put("_age", "age");
		
		methodNames = new String[cfs.size()];
		                      
	}

	
	public void save(Student s) {
		
		String sql = createSQL();
		try {
			Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/hibernate", "root", "root");//這裏是我的數據庫連接信息
			PreparedStatement ps = conn.prepareStatement(sql);
			for(int i = 0;i<methodNames.length;i++){
				try {
					Method m = s.getClass().getMethod(methodNames[i]);//利用反射機制，得到返回值的類型。
					Class r = m.getReturnType();	//取得返回值類型。
					if(r.getName().equals("java.lang.String")){	//比較。
						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);
					}
				} catch (NoSuchMethodException e) {
					e.printStackTrace();
				} catch (SecurityException e) {
					e.printStackTrace();
				} catch (IllegalAccessException e) {
					e.printStackTrace();
				} catch (IllegalArgumentException e) {
					e.printStackTrace();
				} catch (InvocationTargetException e) {
					e.printStackTrace();
				}
				
			}
			ps.executeUpdate();
			ps.close();
			conn.close();
		} catch (SQLException e) {
			
			e.printStackTrace();
		}
		
	}


	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);
			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 + ");" ;
		return sql;
	}
	
	
}

lastest main:

StudentTest.java:

public class StudentTest {
	public static void main(String[]args){
		Student s = new Student();
		s.setId(2);
		s.setName("s2");
		s.setAge(2);
		
		Session session = new Session();
		
		session.save(s);
	}
}