GSON 在 JSF 托管 bean 中不可序列化答案

【问题标题】：GSON not serializable in JSF managed beanGSON 在 JSF 托管 bean 中不可序列化
【发布时间】：2012-07-30 04:02:52
【问题描述】：

我正在使用 GSON。当我启动tomcat时，它给了我错误。我的部分代码：

 @ManagedBean(name = "kpilist")
@ViewScoped
public class KPIListController implements Serializable {

    public List<KPI> getKPI() {
        KPIDAO kpiDAO = new KPIDAO();        
        List<KPI> kpiList = new ArrayList<KPI>();
         Gson gson = new Gson();  
        try {
            kpiList = kpiDAO.getKPI(selectedKPIType);     
            json = gson.toJson(kpiList) ;
            Logger.getLogger(KPIListController.class.getName()).warning("The KPI JSON" + json);
        } catch (SQLException ex) {
            ex.printStackTrace();
            return null;
        }
        return kpiList;
    }

WARNING: Cannot serialize session attribute com.sun.faces.renderkit.ServerSideStateHelper.LogicalViewMap for session 41AC6C7AB4B0869A29778EA4155BFCA1
    java.io.NotSerializableException: com.google.gson.Gson
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1180)
        at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
        at java.util.HashMap.writeObject(HashMap.java:1014)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:962)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
        at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1528)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1493)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
        at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1362)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1170)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
        at java.util.HashMap.writeObject(HashMap.java:1014)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:962)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
        at java.io.ObjectOutputStream.writeArray(ObjectOutputStream.java:1362)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1170)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
        at java.util.HashMap.writeObject(HashMap.java:1014)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:962)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
        at java.util.HashMap.writeObject(HashMap.java:1014)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:601)
        at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:962)
        at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1480)
        at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1416)
        at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1174)
        at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:346)
        at org.apache.catalina.session.StandardSession.writeObject(StandardSession.java:1692)
        at org.apache.catalina.session.StandardSession.writeObjectData(StandardSession.java:1092)
        at org.apache.catalina.session.StandardManager.doUnload(StandardManager.java:411)
        at org.apache.catalina.session.StandardManager.unload(StandardManager.java:353)
        at org.apache.catalina.session.StandardManager.stopInternal(StandardManager.java:497)
        at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:232)
        at org.apache.catalina.core.StandardContext.stopInternal(StandardContext.java:5449)
        at org.apache.catalina.util.LifecycleBase.stop(LifecycleBase.java:232)
        at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1540)
        at org.apache.catalina.core.ContainerBase$StopChild.call(ContainerBase.java:1530)
        at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:334)
        at java.util.concurrent.FutureTask.run(FutureTask.java:166)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
        at java.lang.Thread.run(Thread.java:722)

我在使用 GSON 时是否犯了任何错误？

【问题讨论】：

标签： serialization jsf-2 gson

【解决方案1】：

在您的代码中我看不到它，但看起来有一个成员变量包含Gson，可能是间接的（它甚至可以是一个匿名类实例捕获它）。 AFAIK，例外情况是 Gson 不是 Serializable，这没关系，因为您很可能不想存储它。

【讨论】：

我没有成员变量 Gson ！好吧，虽然我有功能变量。是的，我不想存储它:)！
@Kitex：你不想，但你做到了。使用调试器找出它的来源。异常说得很清楚，查看源代码我无法想象任何其他原因。

【解决方案2】：

您可以尝试使用“瞬态”关键字：

transient Gson gson = new Gson();

这将在序列化过程中忽略“gson”。你可以在这里阅读更多内容：https://www.baeldung.com/java-transient-keyword。

问候。

【讨论】：