深入刨析tomcat 之---第2篇,解决第3章bug 页面不显示内容http://localhost:8080/servlet/ModernServlet?userName=zhangyantao&password=1234

writedby 张艳涛7月2日,

在学习第4张的过程中,发现了前一篇文章写的是关于1,2张的bug不用设置response响应头,需要在servlet的service()方法里面写是错误想

servlet是tomcat的容器内的居住者,主要功能在于交互式地浏览和生成数据，生成动态Web内容,但绝大多数情况下Servlet只用来扩展基于HTTP协议的Web服务器。那么这个servlet实际上是基于http协议的响应体的实现,可以这么说,servlet本质上是对于一个http请求的响应,servlet程序段service()方法,根据http协议来回复客户端的http请求, 对于一个http 请求,回复的内容在哪里? 在response的body里面,如果你是一个网页那么,Content-Type="text/html", response.setContentType("text/html");其实如果你不设置content_type浏览器也能只能的显示为网页;突然发现浏览器很傻_B,如果你返回给浏览器为json格式那么你就给一个Content-Type:

application/json;charset=UTF-8. 让后在写一个{} json串就行了,如果你是个图片
 out = new PrintWriter(socket.getOutputStream());
                if (filePath.endsWith("jpg") || filePath.endsWith("ico")) {    
                    in = new FileInputStream(filePath);//读图片
                    ByteArrayOutputStream baos = new ByteArrayOutputStream();
                    int i=0;
                    while (((i = in.read()) != -1)) {
                        baos.write(i);
                    }
                    byte[] array= baos.toByteArray();
                    out.println("HTTP/1.1 200 OK");
                    out.println("Server: Molly");
                    out.println("Content-Type: image/jpeg");
                    out.println("Content-Length: "+array.length);
                    out.println("");
                    out.flush();
                    socket.getOutputStream().write(array,0,array.length);//写入图片
                    System.out.println(Thread.currentThread().getName());

这样子就成功了,

上一篇文章对于response头信息的设置实现

对于xxx.servlet文件中

    response.setContentType("text/html");
    PrintWriter out = response.getWriter();
    out.println("<html>");

如果out.println("内容"),这个out是socket.getoutputstream的对象,肯定不行,那么就直接发送了,如果保证在头对象之后是这个设计的精髓

这个out对象是

ResponseStream

因为response.getWriter();内容为

HttpResponse类中
@Override
    public PrintWriter getWriter() throws IOException {
        ResponseStream newStream = new ResponseStream(this);
        newStream.setCommit(false);
        OutputStreamWriter osr =
                new OutputStreamWriter(newStream, getCharacterEncoding());
        writer = new ex03.pyrmont.connector.ResponseWriter(osr);
        return writer;
    }

那么久确定了out.println("内容"),的out是ResponseStream ,那么会通过printwrite调用write()

    public void write(byte b[], int off, int len) throws IOException {
        if (closed)
            throw new IOException("responseStream.write.closed");

        int actual = len;
        if ((length > 0) && ((count + len) >= length))
            actual = length - count;
        response.write(b, off, actual);
        count += actual;
        if (actual < len)
            throw new IOException("responseStream.write.count");

    }

那么

HttpResponse类中
    public void write(int b) throws IOException{
        if (bufferCount>=buffer.length) {
            flushBuffer();
        }
        buffer[bufferCount++] = ((byte) b);
        contentCount++;
    }

    public void write(byte b[],int off,int len) throws IOException{
        if (len==0) {
            return;
        }
        if (len<=buffer.length-bufferCount) {
            System.arraycopy(b,off,buffer,bufferCount,len);
            bufferCount += len;
            contentCount += len;
            return;
        }
        flushBuffer(); /** 将buffercount置为0;清空buffer*/
        int iterations= len/buffer.length; /**len太大 看一共有几倍 */
        int leftoverStart=iterations*buffer.length;
        int leftoverLen = len - leftoverStart;
        for (int i = 0; i < iterations; i++) {
            write(b, off + (i * buffer.length), buffer.length);
        }
        if(leftoverLen>0){
            write(b, off + leftoverStart, leftoverLen);
        }
    }

看代码,层层分析之后能发现,最终调用的给buffer数组赋值,只有到flush之后才会发送网络数据,那么,要做的就是先调用sendHeadrs在out.flush();

ServletProcessor类中
            servlet = ((Servlet) myClass.newInstance());
            HttpRequestFacade httpRequestFacade = new HttpRequestFacade(request);
            HttpResponseFacade httpResponseFacade = new HttpResponseFacade(response);
            servlet.service(httpRequestFacade,httpResponseFacade);
            ((HttpResponse) response).finishResponse();

接着

    public void finishResponse() throws IOException {
        sendHeaders();
        if (writer != null) {//   writer = new ex03.pyrmont.connector.ResponseWriter(osr);,这里是
            writer.flush();
            writer.close();
        }
    }

代码和上面的描述一致的

那么,看sendheaders代码

    protected void sendHeaders() throws IOException{
        if (isCommitted()) {
            return;
        }
        OutputStreamWriter osr = null;
        try {
            osr = new OutputStreamWriter(getStream(), getCharacterEncoding());
        } catch (UnsupportedEncodingException e) {
            osr  = new OutputStreamWriter(getStream());
        }
        final PrintWriter outputWriter = new PrintWriter(osr);

        // Send the "Status:" header
        outputWriter.print((this.request.getProtocol()));
        outputWriter.print(" ");
        outputWriter.print(status);
        if(message!=null){
            outputWriter.print(" ");
            outputWriter.print(message);
        }
        outputWriter.print("
");
        if(getContentType()!=null){
            outputWriter.print(" ");
            outputWriter.print("Content-Type: " + getContentType() + "
");
        }
        if (getContentLength() >= 0) {
            outputWriter.print("Content-Length: " + getContentLength() + "
");
        }
        synchronized (headers) {
            Iterator names = headers.keySet().iterator();
            while (names.hasNext()) {
                String name = (String) names.next();
                ArrayList values = (ArrayList) headers.get(name);
                Iterator items = values.iterator();
                while (items.hasNext()) {
                    String value = (String) items.next();
                    outputWriter.print(name);
                    outputWriter.print(": ");
                    outputWriter.print(value);
                    outputWriter.println("
");
                }
            }
        }
        synchronized (cookies) {
            Iterator items = cookies.iterator();
            while (items.hasNext()) {
                Cookie cookie = (Cookie) items.next();
                outputWriter.print(CookieTools.getCookieHeaderName(cookie));
                outputWriter.print(": ");
                outputWriter.print(CookieTools.getCookieHeaderValue(cookie));
                outputWriter.print("
");
            }

        }
        outputWriter.print("
");
        outputWriter.flush();
        committed = true;

    }

这个outwriter直接取值socket.getoutputstream方法

以上代码全来深入刨析tocmat第3章

那么第三章的bug是什么呢?,浏览器执行

http://localhost:8080/servlet/ModernServlet?userName=zhangyantao&password=1234

运行程序页面没反应!!!

给程序打断点也发送sendHeaders,这颗怎么办呢?chrome f12 看不出来什么呢,只能看人才的了

package com.zyt.tomcat.ex03.startup;

import java.io.*;
import java.net.Socket;

public class Client {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket("localhost", 8080);
        System.out.println(socket);
        PrintWriter pw = new PrintWriter(new OutputStreamWriter(socket.getOutputStream()));
        InputStream inputStream = socket.getInputStream();

        pw.println("GET /servlet/ModernServlet?userName=zhangyantao&password=1234l HTTP/1.1");
        pw.println("Host: localhost:8080");
        pw.println("Connection: keep-alive
" +
                "sec-ch-ua: " Not;A Brand";v="99", "Google Chrome";v="91", "Chromium";v="91"
" +
                "sec-ch-ua-mobile: ?0
" +
                "Upgrade-Insecure-Requests: 1
" +
                "User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36
" +
                "Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
" +
                "Sec-Fetch-Site: none
" +
                "Sec-Fetch-Mode: navigate
" +
                "Sec-Fetch-User: ?1
" +
                "Sec-Fetch-Dest: document
" +
                "Accept-Encoding: gzip, deflate, br
" +
                "Accept-Language: zh,zh-TW;q=0.9,en-US;q=0.8,en;q=0.7,zh-CN;q=0.6
" +
                "Cookie: Webstorm-33fda740=2357c3d1-7421-48dd-b63d-9dfa59664905; Idea-d43876f9=54507cfb-5164-4924-84ad-1ddc6e24306e");
        pw.println("

");
        pw.flush();
        int b;
        while ((b=inputStream.read())!=-1){
            System.out.print(((char) b));
        }

    }
}

写了一个client,注意必须是 否则不行

打印的内容为

D:devJDK8injava.exe -javaagent:D:devideaIU-2020.3.1.winlibidea_rt.jar=58985:D:devideaIU-2020.3.1.winin -Dfile.encoding=UTF-8 -classpath D:devJDK8jrelibcharsets.jar;D:devJDK8jrelibdeploy.jar;D:devJDK8jrelibextaccess-bridge-64.jar;D:devJDK8jrelibextcldrdata.jar;D:devJDK8jrelibextdnsns.jar;D:devJDK8jrelibextjaccess.jar;D:devJDK8jrelibextjfxrt.jar;D:devJDK8jrelibextlocaledata.jar;D:devJDK8jrelibext
ashorn.jar;D:devJDK8jrelibextsunec.jar;D:devJDK8jrelibextsunjce_provider.jar;D:devJDK8jrelibextsunmscapi.jar;D:devJDK8jrelibextsunpkcs11.jar;D:devJDK8jrelibextzipfs.jar;D:devJDK8jrelibjavaws.jar;D:devJDK8jrelibjce.jar;D:devJDK8jrelibjfr.jar;D:devJDK8jrelibjfxswt.jar;D:devJDK8jrelibjsse.jar;D:devJDK8jrelibmanagement-agent.jar;D:devJDK8jrelibplugin.jar;D:devJDK8jrelib
esources.jar;D:devJDK8jrelib
t.jar;D:wksp_studydesignbook	argetclasses;D:
epojunitjunit4.11junit-4.11.jar;D:
epoorghamcresthamcrest-core1.3hamcrest-core-1.3.jar;D:
epoorgopenjdkjoljol-core0.10jol-core-0.10.jar;D:
epojavaxservletservlet-api2.3servlet-api-2.3.jar;D:wksp_studydesignbooklibjaas.jar;D:wksp_studydesignbooklibjnet.jar;D:wksp_studydesignbooklibjsse.jar;D:wksp_studydesignbooklibmx4j.jar;D:wksp_studydesignbooklibjcert.jar;D:wksp_studydesignbooklibservlet.jar;D:wksp_studydesignbooklibxercesImpl.jar;D:wksp_studydesignbooklib	omcat-util.jar;D:wksp_studydesignbooklib
aming-common.jar;D:wksp_studydesignbooklibxmlParserAPIs.jar;D:wksp_studydesignbooklibcommons-daemon.jar;D:wksp_studydesignbooklib
aming-factory.jar;D:wksp_studydesignbooklibcommons-logging.jar;D:wksp_studydesignbooklibcommons-modeler.jar;D:wksp_studydesignbooklibcommons-digester.jar;D:wksp_studydesignbooklib
aming-resources.jar;D:wksp_studydesignbooklibcommons-beanutils.jar;D:wksp_studydesignbooklibjakarta-regexp-1.2.jar;D:wksp_studydesignbooklibcommons-collections.jar com.zyt.tomcat.ex03.startup.Client
Socket[addr=localhost/127.0.0.1,port=8080,localport=58988]
<html>
<head>
<title>Modern Servlet</title>
</head>
<body>
<h2>Headers</h2
<br>sec-fetch-mode : navigate
<br>sec-fetch-site : none
<br>accept-language : zh,zh-TW;q=0.9,en-US;q=0.8,en;q=0.7,zh-CN;q=0.6
<br>cookie : Webstorm-33fda740=2357c3d1-7421-48dd-b63d-9dfa59664905; Idea-d43876f9=54507cfb-5164-4924-84ad-1ddc6e24306e
<br>sec-fetch-user : ?1
<br>accept : text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
<br>sec-ch-ua : " Not;A Brand";v="99", "Google Chrome";v="91", "Chromium";v="91"
<br>sec-ch-ua-mobile : ?0
<br>host : localhost:8080
<br>upgrade-insecure-requests : 1
<br>connection : keep-alive
<br>accept-encoding : gzip, deflate, br
<br>user-agent : Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36
<br>sec-fetch-dest : document
<br><h2>Method</h2
<br>GET
<br><h2>Parameters</h2
<br>password : 1234l
<br>userName : zhangyantao
HTTP/1.1 200 OK
Server: Pyrmont Servlet Container


<br><h2>Query String</h2
<br>userName=zhangyantao&password=1234l
<br><h2>Request URI</h2
<br>/servlet/ModernServlet
</body>
</html>

Process finished with exit code 0

发现发送了响应头,但是位置不对,进一步发现是他程序写错了

    public void write(byte b[],int off,int len) throws IOException{
        if (len==0) {
            return;
        }
        if (len<=buffer.length-bufferCount) {
            System.arraycopy(b,off,buffer,bufferCount,len);
            bufferCount += len;
            contentCount += len;
            return;
        }
        flushBuffer(); /** 将buffercount置为0;清空buffer*/
        int iterations= len/buffer.length; /**len太大 看一共有几倍 */
        int leftoverStart=iterations*buffer.length;
        int leftoverLen = len - leftoverStart;
        for (int i = 0; i < iterations; i++) {
            write(b, off + (i * buffer.length), buffer.length);
        }
        if(leftoverLen>0){
            write(b, off + leftoverStart, leftoverLen);
        }
    }

缓存区大小

public class HttpResponse  implements HttpServletResponse {
    private static final int BUFFER_SIZE=1024;

    protected byte[] buffer = new byte[BUFFER_SIZE];
}

如果缓存区满了 ,内容还没写完超过了1024个字节,他就发送了,那么就比响应头的发送提前了,之后才会执行sendheaders和发送后一部分内容

如果你设置  private static final int BUFFER_SIZE=4096;

那么你就获取了一个惊喜

D:devJDK8injava.exe -javaagent:D:devideaIU-2020.3.1.winlibidea_rt.jar=57838:D:devideaIU-2020.3.1.winin -Dfile.encoding=UTF-8 -classpath D:devJDK8jrelibcharsets.jar;D:devJDK8jrelibdeploy.jar;D:devJDK8jrelibextaccess-bridge-64.jar;D:devJDK8jrelibextcldrdata.jar;D:devJDK8jrelibextdnsns.jar;D:devJDK8jrelibextjaccess.jar;D:devJDK8jrelibextjfxrt.jar;D:devJDK8jrelibextlocaledata.jar;D:devJDK8jrelibext
ashorn.jar;D:devJDK8jrelibextsunec.jar;D:devJDK8jrelibextsunjce_provider.jar;D:devJDK8jrelibextsunmscapi.jar;D:devJDK8jrelibextsunpkcs11.jar;D:devJDK8jrelibextzipfs.jar;D:devJDK8jrelibjavaws.jar;D:devJDK8jrelibjce.jar;D:devJDK8jrelibjfr.jar;D:devJDK8jrelibjfxswt.jar;D:devJDK8jrelibjsse.jar;D:devJDK8jrelibmanagement-agent.jar;D:devJDK8jrelibplugin.jar;D:devJDK8jrelib
esources.jar;D:devJDK8jrelib
t.jar;D:wksp_studydesignbook	argetclasses;D:
epojunitjunit4.11junit-4.11.jar;D:
epoorghamcresthamcrest-core1.3hamcrest-core-1.3.jar;D:
epoorgopenjdkjoljol-core0.10jol-core-0.10.jar;D:
epojavaxservletservlet-api2.3servlet-api-2.3.jar;D:wksp_studydesignbooklibjaas.jar;D:wksp_studydesignbooklibjnet.jar;D:wksp_studydesignbooklibjsse.jar;D:wksp_studydesignbooklibmx4j.jar;D:wksp_studydesignbooklibjcert.jar;D:wksp_studydesignbooklibservlet.jar;D:wksp_studydesignbooklibxercesImpl.jar;D:wksp_studydesignbooklib	omcat-util.jar;D:wksp_studydesignbooklib
aming-common.jar;D:wksp_studydesignbooklibxmlParserAPIs.jar;D:wksp_studydesignbooklibcommons-daemon.jar;D:wksp_studydesignbooklib
aming-factory.jar;D:wksp_studydesignbooklibcommons-logging.jar;D:wksp_studydesignbooklibcommons-modeler.jar;D:wksp_studydesignbooklibcommons-digester.jar;D:wksp_studydesignbooklib
aming-resources.jar;D:wksp_studydesignbooklibcommons-beanutils.jar;D:wksp_studydesignbooklibjakarta-regexp-1.2.jar;D:wksp_studydesignbooklibcommons-collections.jar com.zyt.tomcat.ex03.startup.Client
Socket[addr=localhost/127.0.0.1,port=8080,localport=57842]
HTTP/1.1 200 OK
Server: Pyrmont Servlet Container


<html>
<head>
<title>Modern Servlet</title>
</head>
<body>
<h2>Headers</h2
<br>sec-fetch-mode : navigate
<br>sec-fetch-site : none
<br>accept-language : zh,zh-TW;q=0.9,en-US;q=0.8,en;q=0.7,zh-CN;q=0.6
<br>cookie : Webstorm-33fda740=2357c3d1-7421-48dd-b63d-9dfa59664905; Idea-d43876f9=54507cfb-5164-4924-84ad-1ddc6e24306e
<br>sec-fetch-user : ?1
<br>accept : text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
<br>sec-ch-ua : " Not;A Brand";v="99", "Google Chrome";v="91", "Chromium";v="91"
<br>sec-ch-ua-mobile : ?0
<br>host : localhost:8080
<br>upgrade-insecure-requests : 1
<br>connection : keep-alive
<br>accept-encoding : gzip, deflate, br
<br>user-agent : Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/91.0.4472.124 Safari/537.36
<br>sec-fetch-dest : document
<br><h2>Method</h2
<br>GET
<br><h2>Parameters</h2
<br>password : 1234l
<br>userName : zhangyantao
<br><h2>Query String</h2
<br>userName=zhangyantao&password=1234l
<br><h2>Request URI</h2
<br>/servlet/ModernServlet
</body>
</html>

Process finished with exit code 0

浏览器正常显示页面

这书,怎么好呢?解决一个问题太费劲了...一章一个问题,真是费劲呢...,

接下来分析长连接的实现吧,和短链接的区别

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原文地址：https://www.cnblogs.com/zytcomeon/p/14964199.html