模拟hibernate 理解内部实现原理

create table _teacher 
(_id int primary key, _name varchar(20), _title varchar(10));
 
Teacher.java
package org.fp.hibernate.model;
public class Teacher {
private int id;
private String name;
private String title;
public String getTitle() {
return title;
}
public void setTitle(String title) {
this.title = title;
}
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;
}
}
package org.fp.hibernate.test;
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 org.fp.hibernate.model.Teacher;
public class Session {
String tableName = "_Teacher";
// 数据库中的字段名(也就是列名)和类中的属性名称一一对应columnField所以定义为一个Map
Map<String, String> cf = new HashMap<String, String>();
String[] methodNames =null;
// 现在假设我们已经从配置文件中读出来了
public Session() {
cf.put("_id", "id");
cf.put("_name", "name");
cf.put("_title", "title");
methodNames = new String[cf.size()];
}
public void save(Teacher t) throws Exception {
String sql = createSql();
        Class.forName("org.gjt.mm.mysql.Driver");
//Class.forName("com.mysql.jdbc.Driver");
Connection conn = DriverManager.getConnection(
"jdbc:mysql://localhost:3306/hibernate", "root", "root");
PreparedStatement ps =  conn.prepareStatement(sql);
for (int i = 0; i < this.methodNames.length; i++) {
Method m = t.getClass().getMethod(this.methodNames[i]);
Class r = m.getReturnType();
if (r.getName().equals("java.lang.String")) {
String returnValue = (String) m.invoke(t);
ps.setString(i+1, returnValue);
}
if (r.getName().equals("int")) {
Integer returnValue = (Integer) m.invoke(t);
ps.setInt(i+1, returnValue);
}
System.out.println(m.getName()+"|"+r.getName());
}
ps.executeUpdate();
ps.close();
conn.close();
}
private String createSql() {
// TODO Auto-generated method stub
// String sql= insert into tableName(_id,_name,_title) values(?,?,?);
// String sql= insert into tableName(str1) values(str2);
// 拼(_id,_name,_title)
String str1 = "";
int index =0;
/*
 * for (int i = 0; i < cf.keySet().size(); i++) { str1+=cf.keySet()+",";
 * }
 */
for (String s : cf.keySet()) {
String v = cf.get(s);
v= Character.toUpperCase(v.charAt(0))+v.substring(1);//将Key对应的首字母大写
this.methodNames[index]="get"+v;
str1 += s + ",";
index++;
}
str1 = str1.substring(0, str1.length() - 1);
System.out.println("str1=" + str1);
// 拼(?,?,?)
String str2 = "";
for (int i = 0; i < cf.size(); i++) {
str2 += "?,";
}
str2 = str2.substring(0, str2.length() - 1);
System.out.println("str2=" + str2);
String sql = "insert into " + tableName + "(" + str1 + ")" + " values("
+ str2 + ")";
System.out.println("sql=" + sql);
return sql;
}
}
package org.fp.hibernate.test;
import org.fp.hibernate.model.Teacher;
public class TeacherTest {
public static void main(String[] args)throws Exception {
// TODO Auto-generated method stub
Teacher t = new Teacher();
t.setId(3);
t.setName("t3");
t.setTitle("3333");
Session session = new Session();
session.save(t);
}
}
/*str1=_id,_name,_title
str2=?,?,?
sql=insert into _Teacher(_id,_name,_title) values(?,?,?)
getId|int
getName|java.lang.String
getTitle|java.lang.String*/