Question

在使用SAX时，我在Java中遇到了一些奇怪的行为。正在设置值，但在输出时在toString方法中恢复为默认值。这看起来很不寻常。我查看了代码并输出了变量的内存地址，一切都以正确的顺序发生，看似正确完成。其他反序列化的XML元素很好，所以我无法解决它。

我的系统的工作原理如下：有一些抽象方法的类，用户定义属性助手和元素处理程序。元素处理程序处理基于子XML元素的子类的生成，而属性处理程序从构造函数中获取属性列表，并通过属性帮助程序使用它来通过属性帮助程序中实现的抽象方法设置字段。

以下是有问题的课程：

package kokuks.flowmon;

import kokuks.flowmon.FlowmonParser.Handler;

import org.xml.sax.Attributes;

public class FlowProbeFlowStats extends FlowmonParserElement {
    protected final FlowProbe parent;
    protected int flowId = 0;
    protected int packets = 0;
    protected int bytes = 0;
    protected long delayFromFirstProbeSum = 0;
    protected boolean set = false;

    /**
     * @param handler
     * @param parent
     * @param uri
     * @param localName
     * @param qName
     * @param attributes
     */
    FlowProbeFlowStats(Handler handler, FlowProbe parent, String uri, String localName, String qName, Attributes attributes) {
        super(handler, parent, uri, localName, qName, attributes);
        this.parent = parent;
    }

    /**
     * @return the parent
     */
    public FlowProbe getParent() {
        return parent;
    }

    /* (non-Javadoc)
     * @see kokuks.flowmon.FlowmonParserElement#getXMLName()
     */
    @Override
    protected String getXMLName() {
        return "FlowStats";
    }

    /* (non-Javadoc)
     * @see kokuks.flowmon.FlowmonParserElement#createAttributeHandlers()
     */
    @Override
    protected IAttributeHandler[] createAttributeHandlers() {
        return new IAttributeHandler[] {
            new AttributeHandler("flowId") {
                @Override
                public void perform(String argValue) {
                    System.out.println("AH flowId: " + argValue);
                    flowId = Integer.parseInt(argValue);
                    set = true;
                }
            },
            new AttributeHandler("packets") {
                @Override
                public void perform(String argValue) {
                    System.out.println("AH packets: " + argValue);
                    packets = Integer.parseInt(argValue);
                    set = true;
                }
            },
            new AttributeHandler("bytes") {
                @Override
                public void perform(String argValue) {
                    System.out.println("AH bytes: " + argValue);
                    bytes = Integer.parseInt(argValue);
                    set = true;
                }
            },
            new AttributeHandler("delayFromFirstProbeSum") {
                @Override
                public void perform(String argValue) {
                    System.out.println("AH delayFromFirstProbeSum: " + argValue);
                    delayFromFirstProbeSum = Long.parseLong(argValue.substring(0, argValue.length() - 2));
                    set = true;
                }
            }
        };
    }

    /* (non-Javadoc)
     * @see java.lang.Object#toString()
     */
    @Override
    public String toString() {
        return "FlowStats/" + super.toString() + "[flowId: " + flowId + ", packets: " + packets +
        ", bytes: " + bytes + ", delayFromFirstProbeSum: " + delayFromFirstProbeSum + "]";
    }
}

我还有一些调试输出，其中查找属性并调用相关的实现方法。

    if (this instanceof FlowProbeFlowStats) {
        System.out.println("ahaaaa1:: " + this.toString());
    }

    IAttributeHandler[] ahandlers = createAttributeHandlers();

    if (ahandlers != null) {
        Map<String, IAttributeHandler> attributeHandlers = new HashMap<String, IAttributeHandler>(ahandlers.length);
        for (IAttributeHandler ah : ahandlers) {
            attributeHandlers.put(ah.getName(), ah);
        }

        for (int i = 0; i < attributes.getLength(); i++) {
            IAttributeHandler ah = attributeHandlers.get(attributes.getQName(i));
            if (ah == null) {
                throw new IllegalStateException("Attribute helper not found in qName: " + qName +  " for attrib with localName: " + attributes.getLocalName(i) + ", qname*: " + attributes.getQName(i));
            }

            try {
                ah.perform(attributes.getValue(i));
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }

    if (this instanceof FlowProbeFlowStats) {
        System.out.println("ahaaaa2:: " + this.toString());
    }

无论如何，这是输出：

ahaaaa1:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@89cd21[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]
AH flowId: 1
AH packets: 5
AH bytes: 333
AH delayFromFirstProbeSum: 50274395ns
ahaaaa2:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@89cd21[flowId: 1, packets: 5, bytes: 333, delayFromFirstProbeSum: 50274395]
ahaaaa1:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@849f16[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]
AH flowId: 2
AH packets: 5
AH bytes: 333
AH delayFromFirstProbeSum: 50274395ns
ahaaaa2:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@849f16[flowId: 2, packets: 5, bytes: 333, delayFromFirstProbeSum: 50274395]
ahaaaa1:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@825c9d[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]
AH flowId: 3
AH packets: 5
AH bytes: 1082
AH delayFromFirstProbeSum: 0ns
ahaaaa2:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@825c9d[flowId: 3, packets: 5, bytes: 1082, delayFromFirstProbeSum: 0]
ahaaaa1:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@1577d9b[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]
AH flowId: 4
AH packets: 4
AH bytes: 762
AH delayFromFirstProbeSum: 0ns
ahaaaa2:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@1577d9b[flowId: 4, packets: 4, bytes: 762, delayFromFirstProbeSum: 0]
ahaaaa1:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@8097e5[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]
AH flowId: 2
AH packets: 5
AH bytes: 333
AH delayFromFirstProbeSum: 0ns
ahaaaa2:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@8097e5[flowId: 2, packets: 5, bytes: 333, delayFromFirstProbeSum: 0]
ahaaaa1:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@745c78[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]
AH flowId: 4
AH packets: 4
AH bytes: 762
AH delayFromFirstProbeSum: 40615996ns
ahaaaa2:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@745c78[flowId: 4, packets: 4, bytes: 762, delayFromFirstProbeSum: 40615996]
ahaaaa1:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@162e843[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]
AH flowId: 1
AH packets: 5
AH bytes: 333
AH delayFromFirstProbeSum: 0ns
ahaaaa2:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@162e843[flowId: 1, packets: 5, bytes: 333, delayFromFirstProbeSum: 0]
ahaaaa1:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@7e9dfc[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]
AH flowId: 3
AH packets: 5
AH bytes: 1082
AH delayFromFirstProbeSum: 51335996ns
ahaaaa2:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@7e9dfc[flowId: 3, packets: 5, bytes: 1082, delayFromFirstProbeSum: 51335996]
[kks-j~KokuKS~/Names] fmxml:FlowMonitor[FlowStats[Flow[flowID: 1,timeFirstTxPacket: 1011735011,timeLastTxPacket: 1343457103,timeFirstRxPacket: 1021768610,timeLastRxPacket: 1353490702,delaySum: 50274395,jitterSum: 212800,lastDelay: 10033599,txBytes: 333, rxBytes: 333,txPackets: 5,rxPackets: 5,lostPackets: 0,timesForwarded: 0],Flow[flowID: 2,timeFirstTxPacket: 1015259481,timeLastTxPacket: 1543226881,timeFirstRxPacket: 1025293080,timeLastRxPacket: 1553260480,delaySum: 50274395,jitterSum: 212800,lastDelay: 10033599,txBytes: 333, rxBytes: 333,txPackets: 5,rxPackets: 5,lostPackets: 0,timesForwarded: 0],Flow[flowID: 3,timeFirstTxPacket: 1021768610,timeLastTxPacket: 1332941904,timeFirstRxPacket: 1031802209,timeLastRxPacket: 1343457103,delaySum: 51335996,jitterSum: 481600,lastDelay: 10515199,txBytes: 1082, rxBytes: 1082,txPackets: 5,rxPackets: 5,lostPackets: 0,timesForwarded: 0],Flow[flowID: 4,timeFirstTxPacket: 1025293080,timeLastTxPacket: 1332969282,timeFirstRxPacket: 1035326679,timeLastRxPacket: 1343226881,delaySum: 40615996,jitterSum: 291200,lastDelay: 10257599,txBytes: 762, rxBytes: 762,txPackets: 4,rxPackets: 4,lostPackets: 0,timesForwarded: 0]],Ipv4FlowClassifier[Flow[flowId: 4, sourceAddress: 10.1.0.1, destinationAddress: 10.1.0.2, protocol: 6],Flow[flowId: 3, sourceAddress: 10.1.0.1, destinationAddress: 10.1.1.2, protocol: 6],Flow[flowId: 2, sourceAddress: 10.1.0.2, destinationAddress: 10.1.0.1, protocol: 6],Flow[flowId: 1, sourceAddress: 10.1.1.2, destinationAddress: 10.1.0.1, protocol: 6]],FlowProbes[FlowProbe[index: 0, stats: <FlowStats/kokuks.flowmon.FlowProbeFlowStats@89cd21[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0],FlowStats/kokuks.flowmon.FlowProbeFlowStats@849f16[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0],FlowStats/kokuks.flowmon.FlowProbeFlowStats@825c9d[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0],FlowStats/kokuks.flowmon.FlowProbeFlowStats@1577d9b[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]>],FlowProbe[index: 1, stats: <FlowStats/kokuks.flowmon.FlowProbeFlowStats@8097e5[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0],FlowStats/kokuks.flowmon.FlowProbeFlowStats@745c78[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]>],FlowProbe[index: 2, stats: <FlowStats/kokuks.flowmon.FlowProbeFlowStats@162e843[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0],FlowStats/kokuks.flowmon.FlowProbeFlowStats@7e9dfc[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]>]]]

注意记忆值 - 这很奇怪。整个toString输出（来自转换后的根XML元素）位于最后一行。

无论如何，谢谢你的帮助，
克里斯

编辑：我为变量设置了一些不同的默认值，而不是0：

protected final FlowProbe parent;
protected int flowId = 1000;
protected int packets = 1000;
protected int bytes = 1000;
protected long delayFromFirstProbeSum = 1000;
protected boolean set = false;

以下是设置过程中的结果：

ahaaaa1:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@1156508[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]
kokuks.flowmon.FlowProbeFlowStats@1156508: AH flowId: 4
kokuks.flowmon.FlowProbeFlowStats@1156508: AH packets: 5
kokuks.flowmon.FlowProbeFlowStats@1156508: AH bytes: 1082
kokuks.flowmon.FlowProbeFlowStats@1156508: AH delayFromFirstProbeSum: 0ns
ahaaaa2:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@1156508[flowId: 4, packets: 5, bytes: 1082, delayFromFirstProbeSum: 0]

最初发生了一些奇怪的事情，值是0而不是1000.非常奇怪。当涉及到最终输出时，输出的对象的值为1000而不是0（字段默认值的初始值）。

Edit2：我现在在标题中有以下内容：

protected int countdown = 4;

在设置属性时递减。一个例子是：

        new AttributeHandler("packets") {
            @Override
            public void perform(String argValue) {
                synchronized (FlowProbeFlowStats.this) {
                    System.out.println(FlowProbeFlowStats.super.toString() + ": AH packets: " + argValue);
                    packets = Integer.parseInt(argValue);
                    System.out.println("packets set to " + packets);
                    set = true;
                    countdown--;
                }
            }
        },

现在是oString语句：

/* (non-Javadoc)
 * @see java.lang.Object#toString()
 */
@Override
public String toString() {
    return "FlowStats/" + super.toString() + "[flowId: " + flowId + ", packets: " + packets +
    ", bytes: " + bytes + ", delayFromFirstProbeSum: " + delayFromFirstProbeSum +
    ", countdown: " + countdown + "]";
}

打印出来了：

ahaaaa2:: FlowStats/kokuks.flowmon.FlowProbeFlowStats@1b27882[flowId: 1, packets: 5, bytes: 333, delayFromFirstProbeSum: 0, countdown: -4]

...

[kks-j~KokuKS~/Names] fmxml:FlowMonitor[FlowStats[Flow[flowID: 1,timeFirstTxPacket: 1007829288,timeLastTxPacket: 1524157706,timeFirstRxPacket: 1017862887,timeLastRxPacket: 1534191305,delaySum: 50274395,jitterSum: 212800,lastDelay: 10033599,txBytes: 333, rxBytes: 333,txPackets: 5,rxPackets: 5,lostPackets: 0,timesForwarded: 0],Flow[flowID: 2,timeFirstTxPacket: 1010210025,timeLastTxPacket: 1324387511,timeFirstRxPacket: 1020243624,timeLastRxPacket: 1334421110,delaySum: 50274395,jitterSum: 212800,lastDelay: 10033599,txBytes: 333, rxBytes: 333,txPackets: 5,rxPackets: 5,lostPackets: 0,timesForwarded: 0],Flow[flowID: 3,timeFirstTxPacket: 1017862887,timeLastTxPacket: 1313900107,timeFirstRxPacket: 1027896486,timeLastRxPacket: 1324157706,delaySum: 40615996,jitterSum: 291200,lastDelay: 10257599,txBytes: 762, rxBytes: 762,txPackets: 4,rxPackets: 4,lostPackets: 0,timesForwarded: 0],Flow[flowID: 4,timeFirstTxPacket: 1020243624,timeLastTxPacket: 1313872312,timeFirstRxPacket: 1030277223,timeLastRxPacket: 1324387511,delaySum: 51335996,jitterSum: 481600,lastDelay: 10515199,txBytes: 1082, rxBytes: 1082,txPackets: 5,rxPackets: 5,lostPackets: 0,timesForwarded: 0]],Ipv4FlowClassifier[Flow[flowId: 4, sourceAddress: 10.1.0.1, destinationAddress: 10.1.0.2, protocol: 6],Flow[flowId: 3, sourceAddress: 10.1.0.1, destinationAddress: 10.1.1.2, protocol: 6],Flow[flowId: 2, sourceAddress: 10.1.0.2, destinationAddress: 10.1.0.1, protocol: 6],Flow[flowId: 1, sourceAddress: 10.1.1.2, destinationAddress: 10.1.0.1, protocol: 6]],FlowProbes[FlowProbe[index: 0, stats: <FlowStats/kokuks.flowmon.FlowProbeFlowStats@1b0d2d0[flowId: 1000, packets: 1000, bytes: 1000, delayFromFirstProbeSum: 1000, countdown: 4],FlowStats/kokuks.flowmon.FlowProbeFlowStats@83df14[flowId: 1000, packets: 1000, bytes: 1000, delayFromFirstProbeSum: 1000, countdown: 4],FlowStats/kokuks.flowmon.FlowProbeFlowStats@1aabc29[flowId: 1000, packets: 1000, bytes: 1000, delayFromFirstProbeSum: 1000, countdown: 4],FlowStats/kokuks.flowmon.FlowProbeFlowStats@2758d0[flowId: 1000, packets: 1000, bytes: 1000, delayFromFirstProbeSum: 1000, countdown: 4]>],FlowProbe[index: 1, stats: <FlowStats/kokuks.flowmon.FlowProbeFlowStats@137e19e[flowId: 1000, packets: 1000, bytes: 1000, delayFromFirstProbeSum: 1000, countdown: 4],FlowStats/kokuks.flowmon.FlowProbeFlowStats@1bd5f28[flowId: 1000, packets: 1000, bytes: 1000, delayFromFirstProbeSum: 1000, countdown: 4]>],FlowProbe[index: 2, stats: <FlowStats/kokuks.flowmon.FlowProbeFlowStats@1b27882[flowId: 1000, packets: 1000, bytes: 1000, delayFromFirstProbeSum: 1000, countdown: 4],FlowStats/kokuks.flowmon.FlowProbeFlowStats@5b84b[flowId: 1000, packets: 1000, bytes: 1000, delayFromFirstProbeSum: 1000, countdown: 4]>]]]

属性setter和toString中的synchronized语句用于检查JVM错误，但它没有做任何事情。奇怪呃？

编辑3：

我将字段更改为Atomic *。我必须认真对待JVM错误，因为原子字段是最终的并且在内部由默认值设置，并且我得到NullPointerException。

protected final AtomicInteger flowId = new AtomicInteger();
protected final AtomicInteger packets = new AtomicInteger();
protected final AtomicInteger bytes = new AtomicInteger();
protected final AtomicLong delayFromFirstProbeSum = new AtomicLong();

例外：

Exception in thread "FlowMonitor Updater" java.lang.NullPointerException
    at kokuks.flowmon.FlowProbeFlowStats.toString(FlowProbeFlowStats.java:95)

编辑4：我从JDK1.7改为稳定版1.6，同样的问题。

我刚刚想到，也许字段 - 在构造函数中未设置，然后稍后设置。我不确定初始化的顺序，但也许在这种情况下它搞砸了。无论如何，我会把它放在init方法中，看看是否有任何作用。但奇怪的是，它在单个类的情况下不起作用。它适用于其他人。

Answer 1

您的输出有些奇怪：前缀为ahaaaa2的行似乎在前缀为ahaaaa1的行之前打印。但实际上，ahaaaa2行来自前一组值，而ahaaaa1行来自下一组值。

前缀为ahaaaa1的行是具有默认值（0）的行。正如我所料，ahaaaa2的行似乎具有正确的值。我想如果你在System.out.println("ahaaaa2:: " + this.toString())之后添加了一两行换行符，你就会看到输出是正确的。

编辑：好的，我终于看到了这个问题。在（非常难以阅读！）最后一行输出结束时，您再次打印出所有统计数据。您希望看到的地方：

FlowStats/kokuks.flowmon.FlowProbeFlowStats@1577d9b[flowId: 4, packets: 4, bytes: 762, delayFromFirstProbeSum: 0]

你改为：

FlowStats/kokuks.flowmon.FlowProbeFlowStats@1577d9b[flowId: 0, packets: 0, bytes: 0, delayFromFirstProbeSum: 0]

其他FlowProbeFlowStats对象的

等等

我不知道发生了什么，但我也看不到最后一行产生的位置，以及同时FlowProbeFlowStats对象会发生什么。没有看到更多代码，我认为我无法提供帮助。

Answer 2

通过将设置移动到init方法来解决问题，结果发现在构造函数中执行所有操作时会出现一些奇怪现象。因此，当我尝试访问它们时，为什么Atomic *字段为null。发生这种情况是因为它们尚未设置，因为首先是对父构造函数的超级调用。为什么其他元素没问题超出了我的意见，但是修复了它。

XML反序列化器中的奇怪行为

2 个答案: