如何通过从 JSP 页面作为表单参数传递的 Servlet 检索网页？
JSP 页面有一个带有文本框的表单，用于输入作为字符串的 url 和一个提交按钮。该操作由 servlet 执行，该 servlet 从传递的 url 获取网页并显示检索到的网页。
这里我有我的 servlet 代码`
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
* Servlet implementation class Search
*/
@WebServlet("/Search")
public class Search extends HttpServlet {
private static final long serialVersionUID = 1L;
/**
* @see HttpServlet#HttpServlet()
*/
public Search() {
super();
// TODO Auto-generated constructor stub
}
/**
* @param
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
String html = null;
String server = request.getParameter("browsebox");
if(server != null && server !="")
{
response.sendRedirect("browse.jsp");
}
try {
html = getWebPageFromUrl(server);
}catch(Exception e) {
System.err.println(e.toString());
return;
}
response.setHeader("serchbox", server);
response.setContentType("text/html");
PrintWriter out = response.getWriter();
if(html == null) {
out.println("<html>");
out.println("<head><title>Refresher</title></head>");
out.println("<body bgcolor=\"#ffffff\">");
out.println("<p>The servlet has received a POST. This is the reply. </p>");
out.println("</body></html>");
} else {
out.print(html);
}
}
/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// TODO Auto-generated method stub
doGet(request,response);
}
private String getWebPageFromUrl(String urlString) throws Exception {
// Create a URL object from urlString
URL stockURL;
try {
stockURL = new URL(urlString);
} catch (MalformedURLException e) {
String msg = "Invalid url: " + urlString;
throw new Exception(msg);
}
// Open a connection to the URL
URLConnection stockConnection;
try {
stockConnection = stockURL.openConnection();
} catch (IOException e) {
String msg = "Can't open connection to " + urlString;
throw new Exception(msg);
}
// Get the InputStream from the URL connection
InputStream webPageInputStream;
try {
webPageInputStream = stockConnection.getInputStream();
} catch (IOException e) {
// Could be any server error, but the most likely is 404
String msg = "404 File Not Found: " + urlString;
//throw new WebPageGrabberException(msg);
throw new Exception(e.toString());
}
// Read the web page via the InputStream
StringBuffer webPageData = new StringBuffer(32000);
int totalBytesRead = 0;
boolean moreToRead = true;
byte[] readBuf = new byte[4096]; // Read the web page in 4K chunks
while (moreToRead) {
int numBytesRead = 0;
try {
numBytesRead = webPageInputStream.read(readBuf);
} catch (IOException e) {
moreToRead = false;
numBytesRead = -1;
}
if (numBytesRead > 0) {
totalBytesRead += numBytesRead;
webPageData.append(new String(readBuf, 0, numBytesRead));
} else {
moreToRead = false;
}
}
try {
webPageInputStream.close();
} catch (IOException e) {
// Ignore any exception that might occur
}
webPageData.setLength(totalBytesRead);
webPageData.toString();
}
}
提交表单时，我从 servlet 得到空白。