学习java（一）——An Example Using Initialization Parameters

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This example shows the servlet reads the message and the repeats initialization parameters when initialiazed

import javax.servlet.http.*;

import javax.servlet.*;

import java.io.*;

public class ShowMessage extends HttpServlet {

private String message;

private String defaultMessage = "No Message";

private int repeats = 1;

public void init( ServletConfig config ) throws

ServletException {

super.init( config );

message = config.getInitParameter("message");

if( message == null ){

message = defaultMessage;

}

try {

String repeateString = config.getInitParameter("repeats");

repeats = Integer.parseInt(repeateString);

} catch( NumberFormatException e ){

// NumberFormatException handles case where repeatString

// is null *and* case where it is something in an

// illegal format. Either way, do nothing in catch,

// as the previous value (1) for the repeats field will

// remain valid because the Integer.parseInt throws

// the exception *before* the value gets assigned

// to repeats.

}

public void doGet( HttpServletRequest request,

HttpServletResponse response) throws

IOException, ServletException {

response.setContentType("text/html");

PrintWriter writer = response.getWriter();

writer.print("<html><head><title>The showmessage example</title></head>");

writer.print("<body bgcolor="#fdf5e6">");

writer.print("<h1>The showMessage Servlet</h1>");

for( int i=0; i<repeats; i++ ) {

writer.print(message+"<br>");

}

writer.print("</body></html>");

}

}

Core Approach

For complex initializations, store the data in a separate file and use the init
parameters to give the location of that file.