db4o db4o是一个嵌入式的开源对象数据库引擎.对于Java与.NET开发者来说都是一个非常好的对象持久化工具. db4o性能高并且安装简单.

				package com.db4o.f1.chapter6;
				
				public class NotStorable {
				  private int id;
				  private String name;
				  private transient int length;
				
				  public NotStorable(int id,String name) {
				    this.id=id;
				    this.name=name;
				    this.length=name.length();
				  }
				
				  public int getId() {
				    return id;
				  }
				  
				  public String getName() {
				    return name;
				  }  
				
				  public int getLength() {
				    return length;
				  }
				
				  public String toString() {
				    return id+"/"+name+": "+length;
				  }
				}