我正在尝试创建一个简单的HTTP服务器来处理来自浏览器的请求并返回相应的答案。我已经实现了基本连接，但是我无法正确构建返回标头，因此浏览器可以显示服务器的答案（例如从服务器获取.jpg图片并正确显示）。
我认为我遇到的问题与正确构建答案标题有关。我对这方面的经验不多，我将不胜感激。
下面是我的HttpHandler类，它处理来自浏览器的请求并返回答案。我认为这个问题出现在httpHeaderConstructor方法中。
package Server;
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.File;
import java.io.FileInputStream;
import org.apache.commons.io.FilenameUtils;
public class HttpHandler {
public static void httpHandler(BufferedReader clientInput, DataOutputStream serverResponse){
int type_of_method = 0;
String path = new String();
try{
String tmp = clientInput.readLine();
String tmp2 = new String(tmp);
tmp.toUpperCase();
System.out.println("Clients request call:" + tmp);
if(tmp.startsWith("GET"))
type_of_method = 1;
if(type_of_method == 0){
try{
serverResponse.writeBytes(httpHeaderConstructor(501, 0));
serverResponse.close();
return;
}catch(Exception e){
System.out.println("1.Error: " + e.getMessage());
}
}
int start = 0;
int end = 0;
for(int a = 0; a < tmp2.length(); a++){
if(tmp2.charAt(a) == ' ' && start != 0){
end = a;
break;
}
if(tmp2.charAt(a) == ' ' && start == 0){
start = a;
}
}
path = tmp2.substring(start + 2, end);
System.out.println("Requested file path: " + path);
}catch(Exception e){
System.out.println("2.Error (bad request Exception): " + e.getMessage());
}
System.out.println("Client requested: " + new File(path).getAbsolutePath());
sendRequestedFile(path, serverResponse);
}
private static void sendRequestedFile(String filePath, DataOutputStream srvResponse){
FileInputStream requestedFile = null;
try{
requestedFile = new FileInputStream(filePath);
System.out.println("File found and opened successfully");
}catch(Exception e){
try {
System.out.println("Could not find file!");
srvResponse.writeBytes(httpHeaderConstructor(404, 0));
srvResponse.close();
} catch (Exception err) {
System.out.print("Error: Can't send failed response!");
System.out.print("Error message: " + err.getMessage());
}
}
String fileExtension = "." + FilenameUtils.getExtension(filePath);
int fileType = 0;
if(fileExtension.equalsIgnoreCase(".jpg") || fileExtension.equals(".jpeg"))
fileType = 1;
if(fileExtension.equals(".gif"))
fileType = 2;
if(fileExtension.equals(".zip"))
fileType = 3;
try {
srvResponse.writeBytes(httpHeaderConstructor(200, fileType));
srvResponse.close();
requestedFile.close();
} catch (Exception e) {
System.out.println("Error message: " + e.getMessage());
}
}
private static String httpHeaderConstructor(int returnCode, int typeOfFile){
String s = "HTTP/1.0";
switch (returnCode) {
case 200:
s += "200 OK";
break;
case 400:
s += "400 Bad Request";
break;
case 403:
s += "403 Forbidden";
break;
case 404:
s += "404 File not found";
break;
case 500:
s += "500 Internal server error";
break;
case 501:
s += "501 Not implemented";
break;
}
s = s + "\r\n";
s = s + "Connection: closing...\r\n";
s = s + "Server: Java HTTP Server v0.1\r\n";
switch (typeOfFile) {
case 0:
break;
case 1:
s = s + "Content-Type: image/jpeg\r\n";
break;
case 2:
s = s + "Content-Type: image/gif\r\n";
break;
case 3:
s = s + "Content-Type: application/x-zip-compressed\r\n";
break;
default:
s = s + "Content-Type: text/html\r\n";
break;
}
s = s + "\r\n";
System.out.println("The returning header is: " + s);
return s;
}
}
这是程序正在构建的标题：
HTTP/1.0 200 OK
Connection: close
Server: Java HTTP Server v0.1
Content-Type: image/jpeg
这些是浏览器中显示的HTML标记：
<html>
<head></head>
<body>
<img src="http://localhost:6565/Moon.jpg" alt="The image “http://localhost:6565/Moon.jpg” cannot be displayed because it contains errors."></img>
</body>
</html>
当您尝试获取.jpeg图像时会发生这种情况。
答案 0 :(得分：0)
首先，请考虑here
中的此示例响应标头HTTP/1.1 200 OK
Date: Mon, 23 May 2005 22:38:34 GMT
Server: Apache/1.3.3.7 (Unix) (Red-Hat/Linux)
Last-Modified: Wed, 08 Jan 2003 23:11:55 GMT
ETag: "3f80f-1b6-3e1cb03b"
Content-Type: text/html; charset=UTF-8
Content-Length: 131
Connection: close
其次，更改您的功能httpHeaderConstructor
private static String httpHeaderConstructor(
int returnCode, int typeOfFile) {
// You should use a StringBuilder.
StringBuilder sb = new StringBuilder("HTTP/1.0 "); // <--
// Missed
// space.
switch (returnCode) {
case 200:
sb.append("200 OK");
break;
case 400:
sb.append("400 Bad Request");
break;
case 403:
sb.append("403 Forbidden");
break;
case 404:
sb.append("404 File not found");
break;
case 500:
sb.append("500 Internal server error");
break;
case 501:
sb.append("501 Not implemented");
break;
}
sb.append("\r\n");
sb.append("Connection: close\r\n"); // <-- Not closing
sb.append("Server: Java HTTP Server v0.1\r\n");
switch (typeOfFile) {
// case 0: // <-- Not a good idea.
// break;
case 1:
sb.append("Content-Type: image/jpeg\r\n");
break;
case 2:
sb.append("Content-Type: image/gif\r\n");
break;
case 3:
sb.append(
"Content-Type: application/x-zip-compressed\r\n");
break;
default:
sb.append("Content-Type: text/html\r\n");
break;
}
sb.append("\r\n");
System.out.println("The returning header is: " + sb.toString());
return sb.toString();
}