How Tomcat Works

The Request Class

A servlet's service method receives a javax.servlet.ServletRequest instance and a javax.servlet.ServletResponse instance from the servlet container. This is to say that for every HTTP request, a servlet container must construct a ServletRequest object and a ServletResponse object and pass them to the service method of the servlet it is serving.

The ex02.pyrmont.Request class represents a request object to be passed to the servlet's service method. As such, it must implement the javax.servlet.ServletRequest interface. This class has to provide implementations for all methods in the interface. However, we would like to make it very simple and provide the implementations of some of the methods only we leave the full method implementations for the chapters to come. In order to compile the Request class, you need to provide "blank" implementations for those methods. If you look at the Request class in Listing 2.3, you will see that all methods whose signatures return an object instance return a null.

Listing 2.3: The Request class

package ex02.pyrmont;
import java.io.InputStream;
import java.io.IOException;
import java.io.BufferedReader;
import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Locale;
import java.util.Map;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletInputStream;
import javax.servlet.ServletRequest;

public class Request implements ServletRequest {
    private InputStream input;
    private String uri;
    public Request(InputStream input){
        this.input = input;
    }
    public String getUri() {
        return uri;
    }
    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 void parse() {
    // Read a set of characters from the socket
        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());
    }
In addition, the Request class still has the parse and the getUri methods which were discussed in Chapter 1.