NullPointerException 上传文件（struts2 + hibernate）答案

【问题标题】：NullPointerException uploading file (struts2 + hibernate)NullPointerException 上传文件（struts2 + hibernate）
【发布时间】：2012-07-30 18:07:42
【问题描述】：

我得到一个空指针异常，似乎无法解决它。我正在使用 Struts2 和 hibernate。

在我的 ProfileAction 中：

public String profilePhoto() {
    String pathToSaveInDB = null;
    String uploadFolder = null;
    String filePath = null;

    try {
        uploadFolder = "profile_pic";
        filePath = servletRequest.getSession().getServletContext().getRealPath("/") + uploadFolder;
        System.out.println("Server path:" + filePath);
        File fileToCreate = new File(filePath, this.userImageFileName);

        System.out.println(this.userImageFileName);
        System.out.println(this.userImage);

        pathToSaveInDB = uploadFolder + "/" + this.userImageFileName;

        FileUtils.copyFile(this.userImage, fileToCreate);

        System.out.println("user id: " + getId());
        System.out.println("photo path: " + pathToSaveInDB);

    } catch (IOException e) {
        e.printStackTrace();
    }
    profileDAO.updateProfilePhoto(Long.parseLong("1"), "test"); <==== just testing
    return SUCCESS;

}

我的个人资料DAOImpl：

@Override
public void updateProfilePhoto(Long id, String path) {

    String SQL_QUERY = "update Profile set ProfilePhotoPath = :path" +
        " where UserId = :id";
    try {
        System.out.println(SQL_QUERY);
        Query query = session.createQuery(SQL_QUERY);
query.setParameter("id", id);
query.setParameter("path", path);

        int result = query.executeUpdate();
        System.out.println(result);
    } catch (Exception e) {
        transaction.rollback();
        e.printStackTrace();
    } 
}

我的表格：

<s:form action="profilePic" method="post" enctype="multipart/form-data">
            <label for="userImage">Profile Avatar:</label> <br />
            <s:file name="userImage" label="User Image" />
            <s:set name="userId" value="#session.User.id"/>
            <s:hidden name="id" value="%{#userId}" />
            <s:submit value="Upload" />
        </s:form>

错误：

java.lang.NullPointerException
com.fotoalbum.dao.ProfileDAOImpl.updateProfilePhoto(ProfileDAOImpl.java:95)
com.fotoalbum.web.ProfileAction.profilePhoto(ProfileAction.java:89)
sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:60)
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:37)
java.lang.reflect.Method.invoke(Method.java:611)
com.opensymphony.xwork2.DefaultActionInvocation.invokeAction(DefaultActionInvocation.java:453)
com.opensymphony.xwork2.DefaultActionInvocation.invokeActionOnly(DefaultActionInvocation.java:292)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:255)
org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept(AnnotationValidationInterceptor.java:68)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ConversionErrorInterceptor.intercept(ConversionErrorInterceptor.java:138)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:211)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ParametersInterceptor.doIntercept(ParametersInterceptor.java:211)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.StaticParametersInterceptor.intercept(StaticParametersInterceptor.java:190)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
org.apache.struts2.interceptor.MultiselectInterceptor.intercept(MultiselectInterceptor.java:75)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
org.apache.struts2.interceptor.CheckboxInterceptor.intercept(CheckboxInterceptor.java:90)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:320)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ModelDrivenInterceptor.intercept(ModelDrivenInterceptor.java:100)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ScopedModelDrivenInterceptor.intercept(ScopedModelDrivenInterceptor.java:141)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ChainingInterceptor.intercept(ChainingInterceptor.java:145)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.PrepareInterceptor.doIntercept(PrepareInterceptor.java:171)
com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.I18nInterceptor.intercept(I18nInterceptor.java:176)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
org.apache.struts2.interceptor.ServletConfigInterceptor.intercept(ServletConfigInterceptor.java:164)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.AliasInterceptor.intercept(AliasInterceptor.java:192)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
com.opensymphony.xwork2.interceptor.ExceptionMappingInterceptor.intercept(ExceptionMappingInterceptor.java:187)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
org.apache.struts2.interceptor.FileUploadInterceptor.intercept(FileUploadInterceptor.java:320)
com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:249)
org.apache.struts2.impl.StrutsActionProxy.execute(StrutsActionProxy.java:54)
org.apache.struts2.dispatcher.Dispatcher.serviceAction(Dispatcher.java:511)
org.apache.struts2.dispatcher.ng.ExecuteOperations.executeAction(ExecuteOperations.java:77)
org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.doFilter(StrutsPrepareAndExecuteFilter.java:91)

该错误特别指出我的 ProfileAction 中的 profileDAO.updateProfilePhoto(Long.parseLong("1"), "test"); 和 ProfileDAOImpl 中的 transaction.rollback(); 是原因。在此先感谢您的帮助:)

如果您需要我发布更多代码，请告诉我。干杯~

【问题讨论】：

com.fotoalbum.dao.ProfileDAOImpl 类的第 95 行是什么？另外，在 updateProfilePhoto() 中，您在哪里创建会话和事务对象

标签： java hibernate struts2 websphere

【解决方案1】：

我认为你的交易是空的。你从哪里开始交易？

【讨论】：

我对 struts2 和 hibernate 概念还是很陌生。我猜你的问题的答案是 ProfileDAOImpl？
哦，我正在使用 Hibernate Full Plugin。这可以解释一下代码吗？我无法理解的是，我正在使用几乎完全相同的代码来更新我的用户配置文件，并且它可以工作，但是在这种情况下它不起作用。我猜是我的文件上传表单页面是错误的原因。只是猜测。

【解决方案2】：

我认为你的拦截器没有配置好

我遇到了这种问题并通过以下代码清除了.....

动作方法：

public String execute() {

    try {
        String filePath = servletRequest.getSession().getServletContext().getRealPath("/");
        System.out.println("Server path:" + filePath);
        File fileToCreate = new File(filePath, this.userImageFileName);

        FileUtils.copyFile(this.userImage, fileToCreate);
    } catch (Exception e) {
        e.printStackTrace();
        addActionError(e.getMessage());

        return INPUT;
    }
    return SUCCESS;
}

struts.xml：

        <action name="userImage">
        class="FileUploadAction">

        <interceptor-ref name="fileUpload">

        <param name="maximumSize">2097152</param>

        <param name="allowedTypes">

        image/png,image/gif,image/jpeg,image/pjpeg

        </param>

        </interceptor-ref>

        <interceptor-ref name="defaultStack"></interceptor-ref>

        <result name="success">SuccessUserImage.jsp</result>

        <result name="input">UserImage.jsp</result>

【讨论】：