模擬Hibernate中一級緩存的工作原理

/**
 * 本程序通過MyDB模擬數據庫 通過HashMap模擬session緩存
 * 具體過程參看代碼註釋
 */
package com.eh.view;


import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


import org.apache.commons.collections.map.HashedMap;


public class MyCache {


/**
* @param args
*/
private static Map<Integer,Student> map=new HashMap<Integer,Student>();
public static void main(String[] args) {
// TODO Auto-generated method stub
Student s1=getStudentById(1);
System.out.println(s1.getName());


Student s3=getStudentById(1);
System.out.println(s3.getName());

Student s2=getStudentById(2);
System.out.println(s2.getName());
}

public static Student getStudentById(int id){
//首先從緩存中取
if(map.containsKey(id)){
System.out.println("從緩存中取出");
return map.get(id);
}else{
//從數據庫中取出
System.out.println("從數據庫中取出");
Student s=MyDB.getStudentById(id);
//放入緩存
map.put(id, s);
return s;
}

}
}


class MyDB{
private static List<Student> list=new ArrayList<Student>();
static{
Student s1=new Student();
Student s2=new Student();
Student s3=new Student();
s1.setId(1);
s1.setName("大寶");
s2.setId(2);
s2.setName("老寶");
s3.setId(1);
s3.setName("小寶");
list.add(s1);
list.add(s2);
list.add(s3);
}
public static Student getStudentById(int id){
for(Student s:list){
if(id==s.getId()){
return s;
}
}
return null;
}
}


class Student{
private int id;
private String name;
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;
}

}