java - 从套接字流读取对象没有获得正确的值

Question

这个问题已经有答案了:

Java socket/serialization, object won't update (2 个回答)

已关闭 4 年前。

所以我试图为一个类(class)做这个项目，我在其中模拟使用套接字的分布式计算机网络。然后每台计算机都会写入一个包含其 ID 和时间戳的事件对象，并且每台计算机还将读取传入的事件对象并比较自己的事件对象和发送的事件对象之间的时间戳。

我以为一切正常，直到我查看日志，发现有些事情似乎很奇怪。我注意到计算机正在一遍又一遍地读取同一个对象，即使它应该接收其他计算机生成的新事件。

这是生成事件并将其写入套接字的代码

private void generateEvents(Random rand, int numOfEvents) throws IOException {
        int temp;
        while (eventCount < numOfEvents) {
            int choice = rand.nextInt(5);
            synchronized (timestamp) {
                if (choice == 0) {
                    temp = timestamp.get(identifier);
                    ++temp;
                    timestamp.set(identifier, temp);
                    log.write(eventCount + ": " + "Sent to myself. " + timestamp.toString());
                } else {
                    int randC = rand.nextInt(outputClients.size());
                    ClientSocket cc = outputClients.get(randC);
                    Event sentEvent = new Event(identifier, timestamp);
                    log.write(sentEvent.from + "  " + sentEvent.timestamp);
                    cc.out.writeObject(sentEvent);
                    log.write(eventCount + ": " + "Sent to " + randC + ": " + timestamp.toString());
                }
            }
            eventCount++;
            // Add sleep for breathing room
            try {
                Thread.sleep(50);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }
    }

此代码由主计算机线程运行。

这是读取对象的代码

while (isAlive) {
                    Event event;
                    try {
                        event = (Event) in.readObject();
                        if (event != null) {
                            log.write("Reading from " + event.from + ": " + event.timestamp.toString());
                            log.write("Old timestamp: " + timestamp.toString());
                            synchronized (timestamp) {
                                int temp;
                                for (int i = 0; i < timestamp.size(); ++i) {
                                    if (event.getTimestamp().get(i) > timestamp.get(i)) {
                                        timestamp.set(i, event.getTimestamp().get(i));
                                    }
                                }
                                temp = timestamp.get(event.getFromID());
                                ++temp;
                                timestamp.set(event.getFromID(), temp);
                            }
                            log.write("Updated timestamp: " + timestamp.toString());
                        }
                    } catch (ClassNotFoundException e) {
                        // Do nothing
                    } catch (EOFException e) {
                        // Do nothing
                    }

                    try {
                        Thread.sleep(500);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }

                }

此代码由 Computer 类创建的单独线程运行。

您可以在这里查看我的完整代码:https://github.com/nollidnosnhoj/time-table-exchange

因此，当我运行该程序时，我开始看到方便的模式:

Computer is starting!
[0, 0, 0, 0, 0]
Connecting to other computers in network
Connected to computers. Start reading and writing events
0  [0, 0, 0, 0, 0]
0: Sent to 2: [0, 0, 0, 0, 0]
0  [0, 0, 0, 0, 0]
1: Sent to 2: [0, 0, 0, 0, 0]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [0, 0, 0, 0, 0]
Updated timestamp: [0, 0, 0, 0, 1]
0  [0, 0, 0, 0, 1]
2: Sent to 2: [0, 0, 0, 0, 1]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [0, 0, 0, 0, 1]
Updated timestamp: [0, 1, 1, 0, 1]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [0, 1, 1, 0, 1]
Updated timestamp: [1, 1, 1, 3, 1]
0  [1, 1, 1, 3, 1]
3: Sent to 1: [1, 1, 1, 3, 1]
0  [1, 1, 1, 3, 1]
4: Sent to 2: [1, 1, 1, 3, 1]
0  [1, 1, 1, 3, 1]
5: Sent to 3: [1, 1, 1, 3, 1]
0  [1, 1, 1, 3, 1]
6: Sent to 3: [1, 1, 1, 3, 1]
0  [1, 1, 1, 3, 1]
7: Sent to 1: [1, 1, 1, 3, 1]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [1, 1, 1, 3, 1]
Updated timestamp: [1, 1, 1, 3, 2]
0  [1, 1, 1, 3, 2]
8: Sent to 2: [1, 1, 1, 3, 2]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [1, 1, 1, 3, 2]
Updated timestamp: [1, 2, 1, 3, 2]
0  [1, 2, 1, 3, 2]
9: Sent to 1: [1, 2, 1, 3, 2]
10: Sent to myself. [2, 2, 1, 3, 2]
11: Sent to myself. [3, 2, 1, 3, 2]
0  [3, 2, 1, 3, 2]
12: Sent to 2: [3, 2, 1, 3, 2]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [3, 2, 1, 3, 2]
Updated timestamp: [3, 4, 4, 5, 2]
0  [3, 4, 4, 5, 2]
13: Sent to 2: [3, 4, 4, 5, 2]
14: Sent to myself. [4, 4, 4, 5, 2]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [4, 4, 4, 5, 2]
Updated timestamp: [4, 4, 4, 5, 3]
0  [4, 4, 4, 5, 3]
15: Sent to 1: [4, 4, 4, 5, 3]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [4, 4, 4, 5, 3]
Updated timestamp: [4, 5, 4, 5, 3]
0  [4, 5, 4, 5, 3]
16: Sent to 3: [4, 5, 4, 5, 3]
0  [4, 5, 4, 5, 3]
17: Sent to 0: [4, 5, 4, 5, 3]
0  [4, 5, 4, 5, 3]
18: Sent to 1: [4, 5, 4, 5, 3]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [4, 5, 4, 5, 3]
Updated timestamp: [4, 5, 5, 5, 3]
0  [4, 5, 5, 5, 3]
19: Sent to 3: [4, 5, 5, 5, 3]
20: Sent to myself. [5, 5, 5, 5, 3]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [5, 5, 5, 5, 3]
Updated timestamp: [5, 5, 5, 6, 3]
0  [5, 5, 5, 6, 3]
21: Sent to 2: [5, 5, 5, 6, 3]
0  [5, 5, 5, 6, 3]
22: Sent to 1: [5, 5, 5, 6, 3]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [5, 5, 5, 6, 3]
Updated timestamp: [5, 5, 5, 6, 4]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [5, 5, 5, 6, 4]
Updated timestamp: [5, 6, 5, 6, 4]
23: Sent to myself. [6, 6, 5, 6, 4]
0  [6, 6, 5, 6, 4]
24: Sent to 3: [6, 6, 5, 6, 4]
0  [6, 6, 5, 6, 4]
25: Sent to 3: [6, 6, 5, 6, 4]
0  [6, 6, 5, 6, 4]
26: Sent to 3: [6, 6, 5, 6, 4]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [6, 6, 5, 6, 4]
Updated timestamp: [6, 6, 6, 6, 4]
0  [6, 6, 6, 6, 4]
27: Sent to 1: [6, 6, 6, 6, 4]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [6, 6, 6, 6, 4]
Updated timestamp: [6, 6, 6, 7, 4]
0  [6, 6, 6, 7, 4]
28: Sent to 1: [6, 6, 6, 7, 4]
0  [6, 6, 6, 7, 4]
29: Sent to 2: [6, 6, 6, 7, 4]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [6, 6, 6, 7, 4]
Updated timestamp: [6, 6, 6, 7, 5]
0  [6, 6, 6, 7, 5]
30: Sent to 2: [6, 6, 6, 7, 5]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [6, 6, 6, 7, 5]
Updated timestamp: [6, 7, 6, 7, 5]
0  [6, 7, 6, 7, 5]
31: Sent to 1: [6, 7, 6, 7, 5]
32: Sent to myself. [7, 7, 6, 7, 5]
0  [7, 7, 6, 7, 5]
33: Sent to 0: [7, 7, 6, 7, 5]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [7, 7, 6, 7, 5]
Updated timestamp: [7, 7, 7, 7, 5]
0  [7, 7, 7, 7, 5]
34: Sent to 1: [7, 7, 7, 7, 5]
0  [7, 7, 7, 7, 5]
35: Sent to 1: [7, 7, 7, 7, 5]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [7, 7, 7, 7, 5]
Updated timestamp: [7, 7, 7, 8, 5]
0  [7, 7, 7, 8, 5]
36: Sent to 1: [7, 7, 7, 8, 5]
0  [7, 7, 7, 8, 5]
37: Sent to 1: [7, 7, 7, 8, 5]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [7, 7, 7, 8, 5]
Updated timestamp: [7, 7, 7, 8, 6]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [7, 7, 7, 8, 6]
Updated timestamp: [7, 8, 7, 8, 6]
0  [7, 8, 7, 8, 6]
38: Sent to 0: [7, 8, 7, 8, 6]
0  [7, 8, 7, 8, 6]
39: Sent to 2: [7, 8, 7, 8, 6]
0  [7, 8, 7, 8, 6]
40: Sent to 3: [7, 8, 7, 8, 6]
0  [7, 8, 7, 8, 6]
41: Sent to 3: [7, 8, 7, 8, 6]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [7, 8, 7, 8, 6]
Updated timestamp: [7, 8, 8, 8, 6]
42: Sent to myself. [8, 8, 8, 8, 6]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [8, 8, 8, 8, 6]
Updated timestamp: [8, 8, 8, 9, 6]
0  [8, 8, 8, 9, 6]
43: Sent to 3: [8, 8, 8, 9, 6]
0  [8, 8, 8, 9, 6]
44: Sent to 2: [8, 8, 8, 9, 6]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [8, 8, 8, 9, 6]
Updated timestamp: [8, 8, 8, 9, 7]
0  [8, 8, 8, 9, 7]
45: Sent to 0: [8, 8, 8, 9, 7]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [8, 8, 8, 9, 7]
Updated timestamp: [8, 9, 8, 9, 7]
0  [8, 9, 8, 9, 7]
46: Sent to 3: [8, 9, 8, 9, 7]
47: Sent to myself. [9, 9, 8, 9, 7]
0  [9, 9, 8, 9, 7]
48: Sent to 3: [9, 9, 8, 9, 7]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [9, 9, 8, 9, 7]
Updated timestamp: [9, 9, 9, 9, 7]
0  [9, 9, 9, 9, 7]
49: Sent to 0: [9, 9, 9, 9, 7]
0  [9, 9, 9, 9, 7]
50: Sent to 0: [9, 9, 9, 9, 7]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [9, 9, 9, 9, 7]
Updated timestamp: [9, 9, 9, 10, 7]
51: Sent to myself. [10, 9, 9, 10, 7]
0  [10, 9, 9, 10, 7]
52: Sent to 2: [10, 9, 9, 10, 7]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [10, 9, 9, 10, 7]
Updated timestamp: [10, 9, 9, 10, 8]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [10, 9, 9, 10, 8]
Updated timestamp: [10, 10, 9, 10, 8]
53: Sent to myself. [11, 10, 9, 10, 8]
0  [11, 10, 9, 10, 8]
54: Sent to 3: [11, 10, 9, 10, 8]
0  [11, 10, 9, 10, 8]
55: Sent to 1: [11, 10, 9, 10, 8]
56: Sent to myself. [12, 10, 9, 10, 8]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [12, 10, 9, 10, 8]
Updated timestamp: [12, 10, 10, 10, 8]
0  [12, 10, 10, 10, 8]
57: Sent to 1: [12, 10, 10, 10, 8]
0  [12, 10, 10, 10, 8]
58: Sent to 2: [12, 10, 10, 10, 8]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [13, 10, 10, 10, 8]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [13, 10, 10, 10, 8]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [13, 10, 10, 10, 8]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [13, 10, 10, 10, 8]
59: Sent to myself. [13, 10, 10, 10, 8]
Updated timestamp: [13, 10, 10, 10, 9]
Updated timestamp: [13, 11, 10, 10, 9]
Updated timestamp: [13, 11, 11, 11, 9]
Updated timestamp: [13, 11, 11, 11, 9]
0  [13, 11, 11, 11, 9]
60: Sent to 3: [13, 11, 11, 11, 9]
0  [13, 11, 11, 11, 9]
61: Sent to 0: [13, 11, 11, 11, 9]
0  [13, 11, 11, 11, 9]
62: Sent to 2: [13, 11, 11, 11, 9]
0  [13, 11, 11, 11, 9]
63: Sent to 0: [13, 11, 11, 11, 9]
0  [13, 11, 11, 11, 9]
64: Sent to 2: [13, 11, 11, 11, 9]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [13, 11, 11, 11, 9]
Updated timestamp: [13, 11, 11, 12, 9]
0  [13, 11, 11, 12, 9]
65: Sent to 2: [13, 11, 11, 12, 9]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [13, 11, 11, 12, 9]
Updated timestamp: [13, 11, 11, 12, 10]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [13, 11, 11, 12, 10]
Updated timestamp: [13, 12, 11, 12, 10]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [13, 12, 11, 12, 10]
Updated timestamp: [13, 12, 12, 12, 10]
0  [13, 12, 12, 12, 10]
66: Sent to 2: [13, 12, 12, 12, 10]
0  [13, 12, 12, 12, 10]
67: Sent to 1: [13, 12, 12, 12, 10]
0  [13, 12, 12, 12, 10]
68: Sent to 2: [13, 12, 12, 12, 10]
69: Sent to myself. [14, 12, 12, 12, 10]
0  [14, 12, 12, 12, 10]
70: Sent to 1: [14, 12, 12, 12, 10]
0  [14, 12, 12, 12, 10]
71: Sent to 3: [14, 12, 12, 12, 10]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [14, 12, 12, 12, 10]
Updated timestamp: [14, 12, 12, 13, 10]
0  [14, 12, 12, 13, 10]
72: Sent to 2: [14, 12, 12, 13, 10]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [14, 12, 12, 13, 10]
Updated timestamp: [14, 12, 12, 13, 11]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [14, 12, 12, 13, 11]
Updated timestamp: [14, 12, 13, 13, 11]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [14, 12, 13, 13, 11]
Updated timestamp: [14, 13, 13, 13, 11]
0  [14, 13, 13, 13, 11]
73: Sent to 2: [14, 13, 13, 13, 11]
0  [14, 13, 13, 13, 11]
74: Sent to 2: [14, 13, 13, 13, 11]
0  [14, 13, 13, 13, 11]
75: Sent to 1: [14, 13, 13, 13, 11]
76: Sent to myself. [15, 13, 13, 13, 11]
77: Sent to myself. [16, 13, 13, 13, 11]
0  [16, 13, 13, 13, 11]
78: Sent to 0: [16, 13, 13, 13, 11]
0  [16, 13, 13, 13, 11]
79: Sent to 2: [16, 13, 13, 13, 11]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [16, 13, 13, 13, 11]
Updated timestamp: [16, 13, 13, 14, 11]
0  [16, 13, 13, 14, 11]
80: Sent to 0: [16, 13, 13, 14, 11]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [16, 13, 13, 14, 11]
Updated timestamp: [16, 13, 13, 14, 12]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [16, 13, 13, 14, 12]
Updated timestamp: [16, 13, 14, 14, 12]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [16, 13, 14, 14, 12]
Updated timestamp: [16, 14, 14, 14, 12]
0  [16, 14, 14, 14, 12]
81: Sent to 1: [16, 14, 14, 14, 12]
0  [16, 14, 14, 14, 12]
82: Sent to 2: [16, 14, 14, 14, 12]
0  [16, 14, 14, 14, 12]
83: Sent to 3: [16, 14, 14, 14, 12]
84: Sent to myself. [17, 14, 14, 14, 12]
85: Sent to myself. [18, 14, 14, 14, 12]
0  [18, 14, 14, 14, 12]
86: Sent to 2: [18, 14, 14, 14, 12]
0  [18, 14, 14, 14, 12]
87: Sent to 1: [18, 14, 14, 14, 12]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [18, 14, 14, 14, 12]
Updated timestamp: [18, 14, 14, 15, 12]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [18, 14, 14, 15, 12]
Updated timestamp: [18, 14, 14, 15, 13]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [18, 14, 14, 15, 13]
Updated timestamp: [18, 14, 15, 15, 13]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [18, 14, 15, 15, 13]
Updated timestamp: [18, 15, 15, 15, 13]
0  [18, 15, 15, 15, 13]
88: Sent to 1: [18, 15, 15, 15, 13]
0  [18, 15, 15, 15, 13]
89: Sent to 1: [18, 15, 15, 15, 13]
0  [18, 15, 15, 15, 13]
90: Sent to 0: [18, 15, 15, 15, 13]
0  [18, 15, 15, 15, 13]
91: Sent to 1: [18, 15, 15, 15, 13]
0  [18, 15, 15, 15, 13]
92: Sent to 1: [18, 15, 15, 15, 13]
0  [18, 15, 15, 15, 13]
93: Sent to 3: [18, 15, 15, 15, 13]
0  [18, 15, 15, 15, 13]
94: Sent to 1: [18, 15, 15, 15, 13]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [18, 15, 15, 15, 13]
Updated timestamp: [18, 15, 15, 16, 13]
0  [18, 15, 15, 16, 13]
95: Sent to 0: [18, 15, 15, 16, 13]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [18, 15, 15, 16, 13]
Updated timestamp: [18, 15, 15, 16, 14]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [18, 15, 15, 16, 14]
Updated timestamp: [18, 15, 16, 16, 14]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [18, 15, 16, 16, 14]
Updated timestamp: [18, 16, 16, 16, 14]
96: Sent to myself. [19, 16, 16, 16, 14]
0  [19, 16, 16, 16, 14]
97: Sent to 2: [19, 16, 16, 16, 14]
0  [19, 16, 16, 16, 14]
98: Sent to 1: [19, 16, 16, 16, 14]
0  [19, 16, 16, 16, 14]
99: Sent to 2: [19, 16, 16, 16, 14]
Finished generating events
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [19, 16, 16, 16, 14]
Updated timestamp: [19, 16, 16, 17, 14]
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [19, 16, 16, 17, 14]
Updated timestamp: [19, 16, 16, 17, 15]
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [19, 16, 16, 17, 15]
Updated timestamp: [19, 16, 17, 17, 15]
Reading from 1: [0, 0, 1, 0, 0]
Old timestamp: [19, 16, 17, 17, 15]
Updated timestamp: [19, 17, 17, 17, 15]
Notifying controller
Reading from 2: [3, 4, 3, 5, 2]
Old timestamp: [19, 17, 17, 17, 15]
Updated timestamp: [19, 17, 18, 17, 15]
Reading from 3: [1, 1, 0, 2, 0]
Old timestamp: [19, 17, 18, 17, 15]
Updated timestamp: [19, 17, 18, 18, 15]
Continuing reading...
Reading from 4: [0, 0, 0, 0, 0]
Old timestamp: [19, 17, 18, 18, 15]
Updated timestamp: [19, 17, 18, 18, 16]
Computer is tearing down.

只要找到所有以“Reading from”开头的语句，您就会看到该模式。

我认为这与对象写入套接字以及从套接字读取错误数据有关。老实说，我不知道，这让我非常沮丧。

如果您有任何问题，我一定会解答!

Answer 1

找到了我的问题的解决方案。在将对象写入输出流之前，我必须添加 objectoutputstream 重置方法，以便它重置流并且不会从以前的对象回溯。

您可以在这里阅读更多相关信息:Java socket/serialization, object won't update

研究解决方案的力量!