(SJSWS7.0 0) Scripting with servlets - prologue

package com.sun.servlet;  
  
import java.io.*;  
import java.util.*;  
import javax.servlet.*;  
import javax.servlet.http.*;  
  
public abstract class ScriptServlet extends GenericServlet {  
  
    private HashMap<String, Object> _sym = new HashMap<String, Object>();  
  
    public HashMap sym() {  
        return _sym;  
    }  
  
    public void add(String sym, Object fn) {  
        _sym.put(sym.toLowerCase(), fn);  
    }  
  
    public void init() throws ServletException {  
        ServletConfig config = getServletConfig();  
        if (config == null) return;  
        try {  
            String handler = config.getInitParameter("handler");  
            if (handler != null) {  
                ServletContext sc = config.getServletContext();  
                InputStream stream = sc.getResourceAsStream(handler);  
                initialize(handler, read(stream));  
                stream.close();  
            } else  
                System.out.println("No handler");  
        } catch (Exception e) {  
            System.out.println("During ScriptServlet.init(): ");  
            e.printStackTrace();  
        }  
    }  
  
    public abstract void initialize(String handler, Object code) throws Exception;  
  
    public abstract void eval(Object fn, HttpServletRequest request, HttpServletResponse response);  

    public void service(HttpServletRequest request,  HttpServletResponse response)  
        throws IOException, ServletException {  
        service((HttpServletRequest)request, (HttpServletResponse)response);  
    }  
  
    public void service(HttpServletRequest request,  HttpServletResponse response)  
        throws IOException, ServletException {  
        // do we have the named method?  
        if (sym().containsKey(request.getMethod().toLowerCase()))  
            eval(sym().get(request.getMethod().toLowerCase()), request, response);  
        // or are we atleast overriding the service?  
        if (sym().containsKey("service"))  
            eval(sym().get("service"), request, response);  
        else  
            super.service(request, response);  
    }  
  
    public void destroy() {  
        if (sym().containsKey("destroy"))  
            eval(sym().get("destroy"), null, null);  
        else  
            super.destroy();  
    }  
  
    // Library functions that may be faster(performance) to do in java  
    // than in our client languages.  
  
    private static Hashtable<String, Object> _cache = new Hashtable<String, Object>();  
    public static Hashtable<String, Object> cache() {  
        return _cache;  
    }  
    // read all in a file and return.  
    // If required, the client program can override this method to supply compiled  
    // code  
    public Object read(String name)  
        throws IOException {  
        if (_cache.containsKey(name))  
            return (String)_cache.get(name);  
        Object val = read(new FileInputStream(name));  
        _cache.put(name, val);  
        return val;  
    }  
  
    public Object read(InputStream in)  
        throws IOException {  
        StringBuffer sb = new StringBuffer();  
        String line = null;  
        DataInputStream ds = new DataInputStream(in);  
        while ((line = ds.readLine()) != null) {  
            sb.append(line);  
            sb.append("\\n");  
        }  
        return sb.toString();  
    }  
}  
  

package com.sun.servlet;  
  
import java.io.*;  
import javax.servlet.http.*;  
import foo.*;  
  
  
public class FooServlet extends ScriptServlet {  
  
    public static Foo foo = new Foo();  

    // the handler contains the script name, and the code contains the entire script as string  
    public void initialize(String handler, Object code)  
        throws Exception {  
        foo.eval(code, foo.bind("httpservlet", this));  
    }  
  
    public void eval(Object fn, HttpServletRequest request, HttpServletResponse response) {  
        try {  
            if (request == null)  
                foo.eval(fn);  
            else  
                foo.eval(fn, new Object[]{request, response});  
        } catch (Exception e) {  
            e.printStackTrace();  
        }  
    }  
}