相关疑难解决方法(0)

我有一个要求,我需要从网站上下载PDF.PDF需要在代码中生成,我认为这将是freemarker和像iText这样的PDF生成框架的组合.有更好的方法吗？

但是,我的主要问题是如何允许用户通过Spring Controller下载文件？

可能重复:
是否应该在HttpServletResponse.getOutputStream()/.getWriter()上调用.close()？

我负责关闭HttpServletResponse.getOutputStream()(或getWriter()甚至输入流)还是应该将它留给容器？

protected void doGet(HttpServletRequest request, HttpServletResponse response) 
   throws ServletException, IOException {
    OutputStream o = response.getOutputStream();
    ... 
    o.close(); //yes/no ?
}

我写了一个简单的servlet如下:

public class MyServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
           throws ServletException, IOException {
        PrintWriter out = response.getWriter();
        // [do stuff with the PrintWriter]
        out.close();
    }
}

是否有必要关闭PrintWriter出局？如果我不关闭流会对进一步影响什么？

在第15.3.2.3节中支持的处理程序方法参数和 Spring 3.0文档的返回类型,它表示可以将java.io.OutputStream或java.io.Writer指定为使用@RequestMapping注释的方法的参数,以生成响应的内容.这个值是Servlet API公开的原始OutputStream/Writer." 方法是否有责任在编写器完成之前关闭它,或者它应该保持打开状态,而其他一些Spring进程是否会关闭它？

我想HttpServletResponse在其内容(通常是HTML)呈现之后添加cookie .

正如这里所提到的(http://osdir.com/ml/java.jasig.uportal/2005-10/msg00276.html),这里(在刷新标题后,在Java中为响应添加一个cookie？),这个可以通过缓冲响应来实现它不会被刷新并发送到客户端(因为在将报头发送到客户端之后,响应被提交,并且不再有标头,即cookie头,可以发送到客户端).

假设这是目前的目标:我认为实现这一目标的一种可能方法是使用a HttpServletResponseWrapper,我可以覆盖它的flushBuffer()方法并防止将header\content实际刷新到客户端:

public class BufferedHttpServletResponse extends HttpServletResponseWrapper {

    public BufferedHttpServletResponse(HttpServletResponse response) {
        super(response);
    }

    public void flushBuffer() {
    }

}

并将此缓冲响应应用于a Filter,以使用过滤器链的其余部分:

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) {

    HttpServletRequest request = (HttpServletRequest) req;
    HttpServletResponse response = (HttpServletResponse) res;

    BufferedHttpServletResponse bufferedResponse = new BufferedHttpServletResponse(response);

    chain.doFilter(request, bufferedResponse);

    // ... create Cookie and add it to response ... response.addCookie(newCookie)
    // response.flushBuffer() ?        

}

问题:上面还可以,还是完全关闭？响应的缓冲区是否会继续填充内容\标题(并且可能会重新调整大小)直到我 …

如标题中所述，提交HttpServletResponse是什么意思？

我有一些请求拦截器，扩展HandlerInterceptorAdapter，覆盖了postHandle方法。后处理方法采用parameter final HttpServletResponse response。在方法主体中有一条if语句检查if response.isCommitted()，该语句究竟执行什么操作？

private static final String voidResponse = "null";

@Override
    public void postHandle(final HttpServletRequest request, final HttpServletResponse response, final Object handler,
            final ModelAndView modelAndView) throws IOException {
        if (!response.isCommitted()) {
            if (DefaultServletHttpRequestHandler.class == handler.getClass()) {
                return;
            }
            response.setStatus(200);
            response.setCharacterEncoding("UTF-8");
            response.setContentType("application/json");
            try (final Writer writer = response.getWriter()) {
                writer.write(voidResponse);
            }
            log.info("void method called, respond with 200 and null");

            response.flushBuffer();
        }
    }

我正在编写一个简单的代理应用程序，并且希望映射的 url 将由我的控制器处理，但其他 url（包括错误）可以转发到另一个不同的地址。因此，如果找不到资源，我会使用Filter而不是HandlerInterceptorAdapter无法调用，因为某些“资源路径处理程序”会处理它。

期待

http://localhost:8090/upload.html> Filter> > http://localhost:8092/upload.html
http://localhost:8090/files/upload>Controllerhttp://localhost:8092/files/upload

不是

http://localhost:8090/upload.html> Filter> > http://localhost:8092/upload.html
http://localhost:8090/files/upload>Controllerhttp://localhost:8092/files/upload

或者

http://localhost:8090/upload.html>>Interceptor未http://localhost:8090/error找到 http://localhost:8090/files/upload>>Filter​http://localhost:8092/files/upload

演示

Filter我在我的子类中设置了一个WebMvcConfigurerAdapter.

@Configuration
@EnableWebMvc
public class WebConfig extends WebMvcConfigurerAdapter {

    @Bean
    private javax.servlet.Filter proxyFilter() {
        return new OncePerRequestFilter() {
            @Override
            protected void doFilterInternal(HttpServletRequest request, HttpServletResponse response, FilterChain filterChain) throws ServletException, IOException {
                System.out.println("[doFilterInternal]isCommitted=" + response.isCommitted() …

这是我在冲洗时遇到的一些例外情况ServletOutputStream。它不会出现在每个请求中，所以我无法重现它。

java.lang.NullPointerException
    at org.apache.coyote.http11.InternalOutputBuffer.realWriteBytes(InternalOutputBuffer.java:215)
    at org.apache.tomcat.util.buf.ByteChunk.flushBuffer(ByteChunk.java:480)
    at org.apache.coyote.http11.InternalOutputBuffer.flush(InternalOutputBuffer.java:119)
    at org.apache.coyote.http11.AbstractHttp11Processor.action(AbstractHttp11Processor.java:805)
    at org.apache.coyote.Response.action(Response.java:174)
    at org.apache.catalina.connector.OutputBuffer.doFlush(OutputBuffer.java:366)
    at org.apache.catalina.connector.OutputBuffer.flush(OutputBuffer.java:333)
    at org.apache.catalina.connector.CoyoteOutputStream.flush(CoyoteOutputStream.java:101)
    at darshan.HttpRequestHandler.returnResponse(HttpRequester.java:117)

HttpRequester.java ：

private void returnResponse(HttpServletResponse response , String responseStr)
{
    InputStream in = null;
    ServletOutputStream out = null;
    try
    {
        in = new ByteArrayInputStream(responseStr.getBytes("UTF-8"));
        response.setContentLength(responseStr.length());
        out = response.getOutputStream();

        byte[] outputByte = new byte[4096];
        while(in.read(outputByte, 0, 4096) != -1)
        {
            out.write(outputByte, 0, 4096);
        }
    }
    catch(Exception e)
    {
        e.printStackTrace();
    }
    finally
    {
        try
        {
            in.close();
            out.flush();  //<-- Exception at …