在 Struts2 中提交响应后无法调用 sendRedirect()

Question

我在一个小的 Web 应用程序中使用 struts2 和 jasper 报告。尝试导出报告时出现以下错误。报告导出成功，但在日志中打印错误，执行操作后struts也无法重定向到成功页面。

我已经通过互联网搜索了这个，但我无法澄清这一点。任何人都可以帮我澄清这一点。

    ERROR Dispatcher - Exception occurred during processing request: Cannot call sendRedirect() after the response has been committed
java.lang.IllegalStateException: Cannot call sendRedirect() after the response has been committed
   at org.apache.catalina.connector.ResponseFacade.sendRedirect(ResponseFacade.java:482)
   at javax.servlet.http.HttpServletResponseWrapper.sendRedirect(HttpServletResponseWrapper.java:137)
   at org.springframework.security.web.context.SaveContextOnUpdateOrErrorResponseWrapper.sendRedirect   (SaveContextOnUpdateOrErrorResponseWrapper.java:74)
   at org.apache.struts2.dispatcher.ServletRedirectResult.sendRedirect(ServletRedirectResult.java:243)
   at org.apache.struts2.dispatcher.ServletRedirectResult.doExecute(ServletRedirectResult.java:226)
   at org.apache.struts2.dispatcher.StrutsResultSupport.execute(StrutsResultSupport.java:186)
   at org.apache.struts2.dispatcher.ServletRedirectResult.execute(ServletRedirectResult.java:161)
   at com.opensymphony.xwork2.DefaultActionInvocation.executeResult(DefaultActionInvocation.java:367)
   at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:271)
   at org.apache.struts2.interceptor.debugging.DebuggingInterceptor.intercept(DebuggingInterceptor.java:256)
   at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
   at com.opensymphony.xwork2.interceptor.DefaultWorkflowInterceptor.doIntercept(DefaultWorkflowInterceptor.java:176)
   at com.opensymphony.xwork2.interceptor.MethodFilterInterceptor.intercept(MethodFilterInterceptor.java:98)
   at com.opensymphony.xwork2.DefaultActionInvocation.invoke(DefaultActionInvocation.java:242)
   at com.opensymphony.xwork2.validator.ValidationInterceptor.doIntercept(ValidationInterceptor.java:265)
   at org.apache.struts2.interceptor.validation.AnnotationValidationInterceptor.doIntercept   (AnnotationValidationInterceptor.java:68)


<struts>

<package name="user" namespace="/" extends="struts-default">

    <action name="testJPReport" class="testUserSupport" method="exportReportAsPdf">
        <result name="success">report.jsp</result>
    </action>
</package>
</struts>


    <?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
http://www.springframework.org/schema/beans/spring-beans-3.1.xsd">

<bean id="testUserSupport"
      class="net.lavanya.app.lav.report.web.TestUserAction">
</bean>

public class TestUserAction  extends ExportSupport{

public String exportReportAsPdf() {
    Map<String, Object> param = new HashMap<>();
    try {
        DataBeanMaker dataBeanMaker = new DataBeanMaker();
        ArrayList<Test> dataBeanList = dataBeanMaker.getTestDataBeanList();
        processReport(ReportTypeEnum.PDF, dataBeanList, "test", param);

    } catch (Exception exception) {
        exception.printStackTrace();
    }
    return SUCCESS;
}

}

package net.test.app.report.web;


import com.opensymphony.xwork2.ActionSupport;
import net.sf.jasperreports.engine.*;
import net.sf.jasperreports.engine.data.JRBeanCollectionDataSource;
import net.sf.jasperreports.engine.design.JasperDesign;
import net.sf.jasperreports.engine.xml.JRXmlLoader;
import org.apache.struts2.interceptor.ServletRequestAware;
import org.apache.struts2.interceptor.ServletResponseAware;

import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.InputStream;
import java.util.List;
import java.util.Map;

 public class ExportSupport extends ActionSupport implements     ServletResponseAware, ServletRequestAware {

    private HttpServletResponse httpServletResponse;
    private HttpServletRequest httpServletRequest;
    private String contentType = "APPLICATION/OCTET-STREAM";


@Override
public void setServletResponse(HttpServletResponse httpServletResponse) {
    this.httpServletResponse = httpServletResponse;
}

@Override
public void setServletRequest(HttpServletRequest httpServletRequest) {
    this.httpServletRequest = httpServletRequest;
}

    public void processReport(ReportTypeEnum reportTypeEnum, List<?>      beansList, String reportName, Map<String, Object> parameters) throws       Exception {
        switch (reportTypeEnum) {
            case PDF:
                processReportAsPDF(beansList, reportName, parameters);
                break;
            default:
                throw new RuntimeException("Un supported report type");
    }
}

private void processReportAsPDF(List<?> beansList, String reportName, Map<String, Object> parameters) throws Exception {
    System.out.println(">>>>>>>Start processing of pdf report!");

    JRBeanCollectionDataSource beanColDataSource = new JRBeanCollectionDataSource(beansList);
    JasperDesign jasperDesign = JRXmlLoader.load(getJasperFilePath(reportName));
    JasperReport jasperReport = JasperCompileManager.compileReport(jasperDesign);
    JasperPrint jasperPrint = JasperFillManager.fillReport(jasperReport, parameters, beanColDataSource);
    setResponseHeaderData(reportName, ReportTypeEnum.PDF);
    ServletOutputStream sos = httpServletResponse.getOutputStream();
    JasperExportManager.exportReportToPdfStream(jasperPrint, sos);
    sos.flush();
    sos.close();
    httpServletResponse.getOutputStream().flush();
    httpServletResponse.getOutputStream().close();

    System.out.println(">>>>>>>End processing of pdf report!");
    return;

}

private InputStream getJasperFilePath(String reportName) throws FileNotFoundException {
    System.out.println(">>>>>>> Path : " + httpServletRequest.getSession().getServletContext().getRealPath("/reports/" + reportName + ".jrxml"));
    return new FileInputStream(httpServletRequest.getSession().getServletContext().getRealPath("/reports/" + reportName + ".jrxml"));
}

private void setResponseHeaderData(String reportName, ReportTypeEnum reportTypeEnum) {
    httpServletResponse.setContentType(contentType);
    StringBuilder headerBuilder = new StringBuilder();
    headerBuilder.append("Attachment;Filename=").append("\"").append(reportName).append(".").
            append(reportTypeEnum.getReportType()).append("\"");

    httpServletResponse.setHeader("Content-Disposition", headerBuilder.toString());
    System.out.println(">>>>>>>End of setting response headers for report download");
}
}

Answer 1

我在您的代码中找不到sendRedirect。 无论如何，请考虑每个 HTTP 请求只有一个 http 响应，您可能需要在客户端使用一些 JavaScript 解决方案。

导出操作，或通常stream 结果类型操作应如下所示：

 @Action(value = "sample-export", results = { @Result(name = "success", type = "stream", params = {
            "inputName", "inputStream", 
            "contentType",   "${exportContentType}; charset=UTF-8", 
            "Content-Disposition", "attachment; filename=\"${filename}\"", 
            "contentDisposition","attachment; filename=\"${filename}\"", 
            "bufferSize", "2048" }) })
    public String export() throws ClientException {

        inputStream = exportInputStream();

        return SUCCESS;

    }
    //Setter and getters for inputStream (java.io.InputStream)

正如您所见，返回成功不会也不应该将用户重定向到新页面，用户发送请求并获得一个流（例如 PDF）作为结果。

如果您想重定向您需要通过 javascript 执行更多操作，或更改下载步骤，请参阅Is it possible in Struts 2 to have a result that downloads a file (stream) *and* redirects? 这可能会有所帮助。 通过更改下载步骤，我的意思是您可以将文件保存在服务器上的临时位置，将用户重定向到最终页面并将下载链接放在那里。