大家好，之前小弟一直在找尋模擬 session 的方法，在觀摩了 JSPWedget 寫法後發現孫三才講師範例適用在 SessionID,SessionValue 都是單純字串的時候，因為當物件中又指向其他物件時，轉出的 Base64 String 就會變很長(Data Member 沒有 Reference 時，String Length 只有 36 ，比較短)，所以我就寫了一個簡單的程式來測試這種物件網絡情形，並設法還原成原物件，發現 Base64 的確可以做到『深層拷貝』，還原後的物件不失真。 有了這個結論，定義資料庫時 SessionValue 開大一點甚至用 Text Field 就 ok 啦。 以下附上整個程式碼供大家參考：

package io;    import java.io.*;
import com.ucom.util.Base64;    public class TestBase64 {
        public TestBase64() {
        }
        public static void main(String[] args) {
                //Step 1.產生一條蟲，並且連續傳連出六條蟲 (Data Member 是一個 Reference，指向另一個 Object Instance)
                Worm w = new Worm(6, 'A');    
                System.out.println("w="   w);
                //Step 2.將 蟲 物件轉換成 Base64 字串，並觀察其內容 (Object to Base64 String)
                String sBase64 = Base64.encodeObject(w);
                int iLength = sBase64.length();
                System.out.println("sBase64="   sBase64   " ,Length="   iLength);
                //Step 3.把 Base64 字串還原成原來的物件 (Base64 String to Object)
                Worm w2 = (Worm) Base64.decodeToObject(sBase64);  //記得轉型一下!
                System.out.println("w2="   w2);
        }
}    //蟲物件 裡所具備的 Data Member
class Data implements Serializable {
        private int i;
        Data(int i_) {
                i = i_;
        }            public String toString() {
                return Integer.toString(i);
        }
}    //蟲物件
class Worm implements Serializable {
        private static int r() {
                return (int) (Math.random() * 10);
        }
        private Data[] d = {
                new Data(r()), new Data(r()), new Data(r())
        };
        private Worm nextWorm = null;
        private char c;
        Worm(int i, char x) {
                System.out.println("Worm Constructor: "   i   " ,char: "   x);
                c = x;
                if (--i > 0) {
                        nextWorm = new Worm(i, (char) (x   1));  //指向下一條蟲
                }
        }
        public String toString() {
                String s = ":"   c   "(";
                for (int i = 0; i < d.length; i  ) {
                        s  = d[i].toString();
                }
                s  = ")";
                if (nextWorm != null) {
                        s  = nextWorm.toString();
                }
                return s;
        }    }

另外以下是輸出結果：(可以看出轉換前和轉回後物件網絡資料成員的值都是一樣的，A-F 那一些數字) Worm Constructor: 6 ,char: A Worm Constructor: 5 ,char: B Worm Constructor: 4 ,char: C Worm Constructor: 3 ,char: D Worm Constructor: 2 ,char: E Worm Constructor: 1 ,char: F w=:A(903):B(428):C(086):D(298):E(500):F(576) sBase64=rO0ABXNyAAdpby5Xb3JtPC8nAJeequsCAANDAAFjWwABZHQACltMaW8vRGF0YTtMAAhuZXh0V29y bXQACUxpby9Xb3JtO3hwAEF1cgAKW0xpby5EYXRhO cKmLWDFe8FAgAAeHAAAAADc3IAB2lvLkRh dGFw3dTg8QoFAgIAAUkAAWl4cAAAAAlzcQB AAYAAAAAc3EAfgAGAAAAA3NxAH4AAABCdXEAfgAE AAAAA3NxAH4ABgAAAARzcQB AAYAAAACc3EAfgAGAAAACHNxAH4AAABDdXEAfgAEAAAAA3NxAH4A BgAAAABzcQB AAYAAAAIc3EAfgAGAAAABnNxAH4AAABEdXEAfgAEAAAAA3NxAH4ABgAAAAJzcQB AAYAAAAJc3EAfgAGAAAACHNxAH4AAABFdXEAfgAEAAAAA3NxAH4ABgAAAAVzcQB AAYAAAAAc3EA fgAGAAAAAHNxAH4AAABGdXEAfgAEAAAAA3NxAH4ABgAAAAVzcQB AAYAAAAHc3EAfgAGAAAABnA= ,Length=538 w2=:A(903):B(428):C(086):D(298):E(500):F(576) JackTasy

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JackTasy