java是现在很受欢迎的开发语言，广泛的应用于生活中，我们使用java可以开发小程序，网页，小游戏等，也可以开发服务器，那java web服务器怎么写?下面来我们就来给大家讲解一下。
一、程序执行步骤
1.创建一个ServerSocket对象;
2.调用ServerSocket对象的accept方法，等待连接，连接成功会返回一个Socket对象，否则一直阻塞等待;
3.从Socket对象中获取InputStream和OutputStream字节流，这两个流分别对应request请求和response响应;
4.处理请求：读取InputStream字节流信息，转成字符串形式，并解析，这里的解析比较简单，仅仅获取uri(统一资源标识符)信息;
5.处理响应：根据解析出来的uri信息，从WEB_ROOT目录中寻找请求的资源资源文件, 读取资源文件，并将其写入到OutputStream字节流中;
6.关闭Socket对象;
7.转到步骤2，继续等待连接请求;
二、代码实现
服务器实现：
package ex01.pyrmont;
import java.net.Socket;
import java.net.ServerSocket;
import java.net.InetAddress;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.IOException;
import java.io.File;
public class HttpServer
{
/**
* WEB_ROOT是HTML和其它文件存放的目录. 这里的WEB_ROOT为工作目录下的webroot目录
*/
public static final String WEB_ROOT = System.getProperty("user.dir") + File.separator + "webroot";
// 关闭服务命令
private static final String SHUTDOWN_COMMAND = "/SHUTDOWN";
public static void main(String[] args)
{
HttpServer server = new HttpServer();
//等待连接请求
server.await();
}
public void await ()
{
ServerSocket serverSocket = null;
int port = 8080;
try
{
//服务器套接字对象
serverSocket = new ServerSocket(port, 1, InetAddress.getByName("127.0.0.1"));
}
catch (IOException e)
{
e.printStackTrace();
System.exit(1);
}
// 循环等待一个请求
while (true)
{
Socket socket = null;
InputStream input = null;
OutputStream output = null;
try
{
//等待连接，连接成功后，返回一个Socket对象
socket = serverSocket.accept();
input = socket.getInputStream();
output = socket.getOutputStream();
// 创建Request对象并解析
Request request = new Request(input);
request.parse();
// 检查是否是关闭服务命令
if (request.getUri()
.equals(SHUTDOWN_COMMAND))
{
break;
}
// 创建 Response 对象
Response response = new Response(output);
response.setRequest(request);
response.sendStaticResource();
// 关闭 socket 对象
socket.close();
}
catch (Exception e)
{
e.printStackTrace();
continue;
}
}
}
}Request类：
package ex01.pyrmont;
import java.io.InputStream;
import java.io.IOException;
public class Request
{
private InputStream input;
private String uri;
public Request(InputStream input)
{
this.input = input;
}
//从InputStream中读取request信息，并从request中获取uri值
public void parse()
{
StringBuffer request = new StringBuffer(2048);
int i;
byte[] buffer = new byte[2048];
try
{
i = input.read(buffer);
}
catch (IOException e)
{
e.printStackTrace();
i = -1;
}
for (int j = 0; j < i; j++)
{
request.append((char) buffer[j]);
}
System.out.print(request.toString());
uri = parseUri(request.toString());
}
/**
*
* requestString形式如下：
* GET /index.html HTTP/1.1
* Host: localhost:8080
* Connection: keep-alive
* Cache-Control: max-age=0
* ...
* 该函数目的就是为了获取/index.html字符串
*/
private String parseUri(String requestString)
{
int index1, index2;
index1 = requestString.indexOf(' ');
if (index1 != -1)
{
index2 = requestString.indexOf(' ', index1 + 1);
if (index2 > index1)
return requestString.substring(index1 + 1, index2);
}
return null;
}
public String getUri()
{
return uri;
}
}Response类：
package ex01.pyrmont;
import java.io.OutputStream;
import java.io.IOException;
import java.io.FileInputStream;
import java.io.File;
/*
HTTP Response = Status-Line
*(( general-header | response-header | entity-header ) CRLF)
CRLF
[ message-body ]
Status-Line = HTTP-Version SP Status-Code SP Reason-Phrase CRLF
*/
public class Response
{
private static final int BUFFER_SIZE = 1024;
Request request;
OutputStream output;
public Response(OutputStream output)
{
this.output = output;
}
public void setRequest(Request request)
{
this.request = request;
}
public void sendStaticResource() throws IOException
{
byte[] bytes = new byte[BUFFER_SIZE];
FileInputStream fis = null;
try
{
//将web文件写入到OutputStream字节流中
File file = new File(HttpServer.WEB_ROOT, request.getUri());
if (file.exists())
{
fis = new FileInputStream(file);
int ch = fis.read(bytes, 0, BUFFER_SIZE);
while (ch != -1)
{
output.write(bytes, 0, ch);
ch = fis.read(bytes, 0, BUFFER_SIZE);
}
}
else
{
// file not found
String errorMessage = "HTTP/1.1 404 File Not Found\r\n" + "Content-Type: text/html\r\n" +
"Content-Length: 23\r\n" + "\r\n" + "<h1>File Not Found</h1>";
output.write(errorMessage.getBytes());
}
}
catch (Exception e)
{
// thrown if cannot instantiate a File object
System.out.println(e.toString());
}
finally
{
if (fis != null)
fis.close();
}
}
}三、结果测试
访问存在的资源文件(注意存放在工程目录的webroot文件夹里)：
访问不存在的资源文件：
关闭服务器：
这样就完成了java web服务器的开发，其实只要学java，你会发现用java可以开发很多应用出来哦!最后大家如果想要了解更多java实例知识，敬请关注奇Q工具网。
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