Question

这是我在刷新ServletOutputStream时遇到的异常。它不会在每个请求中发生，因此我无法重现它。

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 this line
            out.close();
        }
        catch (Exception e) 
        {
            e.printStackTrace();
        }
    }
}

此错误的任何解决方案???

Answer 1

您的代码不需要在输入或输出流上调用flush或close。 servlet容器将为您进行冲洗和关闭。

有时需要进行手动冲洗呼叫的角落情况，但这不是其中之一。但是，在其中任何一个上调用close都不是一个好主意，并且可能会在tomcat中触发导致异常的错误状态。

请参阅Should one call .close() on HttpServletResponse.getOutputStream()/.getWriter()?

Answer 2

这里你可能在最后一个块中写入内容长度，因为它可能读取少于4096bytes

byte[] outputByte = new byte[4096];
    while(in.read(outputByte, 0, 4096) != -1)
    {
        out.write(outputByte, 0, 4096);
    }

刷新ServletOutputStream时出现Nullpointer异常

2 个答案: