在上次Java Socket现实简单的HTTP服务我们实现了简单的HTTP服务，它可以用来模拟HTTP服务，用它可以截获HTTP请求的原始码流，让我们很清楚的了解到我们向服务发的HTTP消息的结构，对HTTP请求消息有个清晰的认识。这一节我想写了一个客户的程序，就是用来模拟浏览器，用来向服务器发送HTTP请求，最得要的是可以用它来显示服务器发回来的HTTP响应消息的一般结构。
下面是代码实现：
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStreamWriter;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
import java.util.ArrayList;
/**
* 一个简单的HTTP客户端，发送HTTP请求，模拟浏览器
* 可打印服务器发送过来的HTTP消息
*/
public class SimpleHttpClient {
private static String encoding = "GBK";
public static void main(String[] args) {
try {
Socket s = new Socket(InetAddress.getLocalHost(), 8080);
OutputStreamWriter osw = new OutputStreamWriter(s.getOutputStream());
StringBuffer sb = new StringBuffer();
sb.append("GET /HttpStream/gb2312.jsp HTTP/1.1\r\n");
sb.append("Host: localhost:8088\r\n");
sb.append("Connection: Keep-Alive\r\n");
//注，这是关键的关键，忘了这里让我搞了半个小时。这里一定要一个回车换行，表示消息头完，不然服务器会等待
sb.append("\r\n");
osw.write(sb.toString());
osw.flush();
//--输出服务器传回的消息的头信息
InputStream is = s.getInputStream();
String line = null;
int contentLength = 0;//服务器发送回来的消息长度
// 读取所有服务器发送过来的请求参数头部信息
do {
line = readLine(is, 0);
//如果有Content-Length消息头时取出
if (line.startsWith("Content-Length")) {
contentLength = Integer.parseInt(line.split(":")[1].trim());
}
//打印请求部信息
System.out.print(line);
//如果遇到了一个单独的回车换行，则表示请求头结束
} while (!line.equals("\r\n"));
//--输消息的体
System.out.print(readLine(is, contentLength));
//关闭流
is.close();
} catch (UnknownHostException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
/*
* 这里我们自己模拟读取一行，因为如果使用API中的BufferedReader时，它是读取到一个回车换行后
* 才返回，否则如果没有读取，则一直阻塞，直接服务器超时自动关闭为止，如果此时还使用BufferedReader
* 来读时，因为读到最后一行时，最后一行后不会有回车换行符，所以就会等待。如果使用服务器发送回来的
* 消息头里的Content-Length来截取消息体，这样就不会阻塞
*
* contentLe 参数 如果为0时，表示读头，读时我们还是一行一行的返回；如果不为0，表示读消息体，
* 时我们根据消息体的长度来读完消息体后，客户端自动关闭流，这样不用先到服务器超时来关闭。
*/
private static String readLine(InputStream is, int contentLe) throws IOException {
ArrayList lineByteList = new ArrayList();
byte readByte;
int total = 0;
if (contentLe != 0) {
do {
readByte = (byte) is.read();
lineByteList.add(Byte.valueOf(readByte));
total++;
} while (total < contentLe);//消息体读还未读完
} else {
do {
readByte = (byte) is.read();
lineByteList.add(Byte.valueOf(readByte));
} while (readByte != 10);
}
byte[] tmpByteArr = new byte[lineByteList.size()];
for (int i = 0; i < lineByteList.size(); i++) {
tmpByteArr[i] = ((Byte) lineByteList.get(i)).byteValue();
}
lineByteList.clear();
return new String(tmpByteArr, encoding);
}
}
运行时访问一个页面打印如下：
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下面来个文件下载的看怎么样?
请求的Jsp页面如下：
<%@page import="java.io.InputStream" contentType="text/html; charset=GB2312"%>
<%@page import="java.io.FileInputStream"%>
<%@page import="java.io.OutputStream"%><html>
<body> <br>
<%
try {
InputStream is = new FileInputStream("e:/tmp/file2.txt");
OutputStream os = response.getOutputStream();
byte[] readContent = new byte[1024];
int readCount = 0;
while (is.available() > 0) {
readCount = is.read(readContent);
os.write(readContent, 0, readCount);
}
is.close();
//注这里一定要关闭，不然的话抛异常，异常请见下面，原因就是response.getWriter()
//与response.getOutputStream()不能同时使用，如果在这里关闭了，前面与后面向
//out对象里写的数据就不会刷新到客户端了，只有向response.getOutputStream()写的
//数据会输出到客户端。
os.close();
} catch (Exception e) {
e.printStackTrace();
}
%>
</body>
</html>
如里上面Jsp下载页面中的 os.close() 注释掉的话会抛如下异常：
exception
org.apache.jasper.JasperException: getOutputStream() has already been called for this response
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:476)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:383)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause
java.lang.IllegalStateException: getOutputStream() has already been called for this response
org.apache.catalina.connector.Response.getWriter(Response.java:601)
org.apache.catalina.connector.ResponseFacade.getWriter(ResponseFacade.java:196)
org.apache.jasper.runtime.JspWriterImpl.initOut(JspWriterImpl.java:125)
org.apache.jasper.runtime.JspWriterImpl.flushBuffer(JspWriterImpl.java:118)
org.apache.jasper.runtime.PageContextImpl.release(PageContextImpl.java:185)
org.apache.jasper.runtime.JspFactoryImpl.internalReleasePageContext(JspFactoryImpl.java:116)
org.apache.jasper.runtime.JspFactoryImpl.releasePageContext(JspFactoryImpl.java:76)
org.apache.jsp.gb2312_jsp._jspService(gb2312_jsp.java:78)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:328)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:315)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
以下是服务器经过编译生成的servlet类文件：
package org.apache.jsp;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.jsp.*;
import java.io.InputStream;
import java.io.FileInputStream;
import java.io.OutputStream;
public final class gb2312_jsp extends org.apache.jasper.runtime.HttpJspBase
implements org.apache.jasper.runtime.JspSourceDependent {
private static java.util.List _jspx_dependants;
public Object getDependants() {
return _jspx_dependants;
}
public void _jspService(HttpServletRequest request, HttpServletResponse response)
throws java.io.IOException, ServletException {
JspFactory _jspxFactory = null;
PageContext pageContext = null;
HttpSession session = null;
ServletContext application = null;
ServletConfig config = null;
JspWriter out = null;
Object page = this;
JspWriter _jspx_out = null;
PageContext _jspx_page_context = null;
try {
_jspxFactory = JspFactory.getDefaultFactory();
response.setContentType("text/html; charset=GB2312");
pageContext = _jspxFactory.getPageContext(this, request, response,
null, true, 8192, true);
_jspx_page_context = pageContext;
application = pageContext.getServletContext();
config = pageContext.getServletConfig();
session = pageContext.getSession();
out = pageContext.getOut();
_jspx_out = out;
out.write("\r\n");
out.write("\r\n");
out.write("\r\n");
out.write("<html>\r\n");
out.write("\t<body> <br>\r\n");
out.write("\t\t");
try {
InputStream is = new FileInputStream("e:/tmp/file2.txt");
OutputStream os = response.getOutputStream();
byte[] readContent = new byte[1024];
int readCount = 0;
while (is.available() > 0) {
readCount = is.read(readContent);
os.write(readContent, 0, readCount);
}
is.close();
//注这里一定要关闭，不然的话抛异常，异常请见下面，原因就是response.getWriter()
//与response.getOutputStream()不能同时使用，如果在这里关闭了，前面与后面向
//out对象里写的数据就不会刷新到客户端了，只有向response.getOutputStream()写的
//数据会输出到客户端。
os.close();
} catch (Exception e) {
e.printStackTrace();
}
out.write("\r\n");
out.write("\t</body>\r\n");
out.write("</html>");
} catch (Throwable t) {
if (!(t instanceof SkipPageException)){
out = _jspx_out;
if (out != null && out.getBufferSize() != 0)
out.clearBuffer();
if (_jspx_page_context != null) _jspx_page_context.handlePageException(t);
}
} finally {
if (_jspxFactory != null) _jspxFactory.releasePageContext(_jspx_page_context);
}
}
}
最后是服务向客户端输出的码流如下：
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