Connecting Java to CGI

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<Form method="GET" ACTION="/cgi-bin/Listmgr2.exe">
<P>Name: <INPUT TYPE = "text" NAME = "name"
VALUE = "" size = "40"></p>
<P>Email Address: <INPUT TYPE = "text"
NAME = "email" VALUE = "" size = "40"></p>
<p><input type = "submit" name = "submit" > </p>
</Form>

//: EncodeDemo.java
// Demonstration of URLEncoder.encode()
import java.net.*;
 
public class EncodeDemo {
  public static void main(String[] args) {
    String s = "";
    for(int i = 0; i < args.length; i++)
      s += args[i] + " ";
    s = URLEncoder.encode(s.trim());
    System.out.println(s);
  }
} ///:~ 

//: NameSender2.java
// An applet that sends an email address
// via a CGI GET, using Java 1.02.
import java.awt.*;
import java.applet.*;
import java.net.*;
import java.io.*;
 
public class NameSender2 extends Applet {
  final String CGIProgram = "Listmgr2.exe";
  Button send = new Button(
    "Add email address to mailing list");
  TextField name = new TextField(
    "type your name here", 40),
    email = new TextField(
    "type your email address here", 40);
  String str = new String();
  Label l = new Label(), l2 = new Label();
  int vcount = 0;
  public void init() {
    setLayout(new BorderLayout());
    Panel p = new Panel();
    p.setLayout(new GridLayout(3, 1));
    p.add(name);
    p.add(email);
    p.add(send);
    add("North", p);
    Panel labels = new Panel();
    labels.setLayout(new GridLayout(2, 1));
    labels.add(l);
    labels.add(l2);
    add("Center", labels);
    l.setText("Ready to send email address");
  }
  public boolean action (Event evt, Object arg) {
    if(evt.target.equals(send)) {
      l2.setText("");
      // Check for errors in data:
      if(name.getText().trim()
         .indexOf(' ') == -1) {
        l.setText(
          "Please give first and last name");
        l2.setText("");
        return true;
      }
      str = email.getText().trim();
      if(str.indexOf(' ') != -1) {
        l.setText(
          "Spaces not allowed in email name");
        l2.setText("");
        return true;
      }
      if(str.indexOf(',') != -1) {
        l.setText(
          "Commas not allowed in email name");
        return true;
      }
      if(str.indexOf('@') == -1) {
        l.setText("Email name must include '@'");
        l2.setText("");
        return true;
      }
      if(str.indexOf('@') == 0) {
        l.setText(
          "Name must preceed '@' in email name");
        l2.setText("");
        return true;
      }
      String end =
        str.substring(str.indexOf('@'));
      if(end.indexOf('.') == -1) {
        l.setText("Portion after '@' must " +
          "have an extension, such as '.com'");
        l2.setText("");
        return true;
      }
      // Build and encode the email data:
      String emailData =
        "name=" + URLEncoder.encode(
          name.getText().trim()) +
        "&email=" + URLEncoder.encode(
          email.getText().trim().toLowerCase()) +
        "&submit=Submit";
      // Send the name using CGI's GET process:
      try {
        l.setText("Sending...");
        URL u = new URL(
          getDocumentBase(), "cgi-bin/" +
          CGIProgram + "?" + emailData);
        l.setText("Sent: " + email.getText());
        send.setLabel("Re-send");
        l2.setText(
          "Waiting for reply " + ++vcount);
        DataInputStream server =
          new DataInputStream(u.openStream());
        String line;
        while((line = server.readLine()) != null)
          l2.setText(line);
      } catch(MalformedURLException e) {
        l.setText("Bad URl");
      } catch(IOException e) {
        l.setText("IO Exception");
      }
    }
    else return super.action(evt, arg);
    return true;
  }
} ///:~ 

      String emailData =
        "name=" + URLEncoder.encode(
          name.getText().trim()) +
        "&email=" + URLEncoder.encode(
          email.getText().trim().toLowerCase()) +
        "&submit=Submit";
      // Send the name using CGI's GET process:
      try {
        l.setText("Sending...");
        URL u = new URL(
          getDocumentBase(), "cgi-bin/" +
          CGIProgram + "?" + emailData);
        l.setText("Sent: " + email.getText());
        send.setLabel("Re-send");
        l2.setText(
          "Waiting for reply " + ++vcount);
        DataInputStream server =
          new DataInputStream(u.openStream());
        String line;
        while((line = server.readLine()) != null)
          l2.setText(line); <p><tt>        // ... </tt></p>

Displaying
a Web page from within an applet

//: ShowHTML.java
import java.awt.*;
import java.applet.*;
import java.net.*;
import java.io.*;
 
public class ShowHTML extends Applet {
  static final String CGIProgram = "MyCGIProgram";
  Button send = new Button("Go");
  Label l = new Label();
  public void init() {
    add(send);
    add(l);
  }
  public boolean action (Event evt, Object arg) {
    if(evt.target.equals(send)) {
      try {
        // This could be an HTML page instead of
        // a CGI program. Notice that this CGI 
        // program doesn't use arguments, but 
        // you can add them in the usual way.
        URL u = new URL(
          getDocumentBase(),
          "cgi-bin/" + CGIProgram);
        // Display the output of the URL using
        // the Web browser, as an ordinary page:
        getAppletContext().showDocument(u);
      } catch(Exception e) {
        l.setText(e.toString());
      }
    }
    else return super.action(evt, arg);
    return true;
  }
} ///:~ 

//: CGITools.h
// Automatically extracts and decodes data
// from CGI GETs and POSTs. Tested with GNU C++ 
// (available for most server machines).
#include <string.h>
#include <vector> // STL vector
using namespace std;
 
// A class to hold a single name-value pair from
// a CGI query. CGI_vector holds Pair objects and
// returns them from its operator[].
class Pair {
  char* nm;
  char* val;
public:
  Pair() { nm = val = 0; }
  Pair(char* name, char* value) {
    // Creates new memory:
    nm = decodeURLString(name);
    val = decodeURLString(value);
  }
  const char* name() const { return nm; }
  const char* value() const { return val; }
  // Test for "emptiness"
  bool empty() const {
    return (nm == 0) || (val == 0);
  }
  // Automatic type conversion for boolean test:
  operator bool() const {
    return (nm != 0) && (val != 0);
  }
  // The following constructors & destructor are
  // necessary for bookkeeping in C++.
  // Copy-constructor:
  Pair(const Pair& p) {
    if(p.nm == 0 || p.val == 0) {
      nm = val = 0;
    } else {
      // Create storage & copy rhs values:
      nm = new char[strlen(p.nm) + 1];
      strcpy(nm, p.nm);
      val = new char[strlen(p.val) + 1];
      strcpy(val, p.val);
    }
  }
  // Assignment operator:
  Pair& operator=(const Pair& p) {
    // Clean up old lvalues:
    delete nm;
    delete val;
    if(p.nm == 0 || p.val == 0) {
      nm = val = 0;
    } else {
      // Create storage & copy rhs values:
      nm = new char[strlen(p.nm) + 1];
      strcpy(nm, p.nm);
      val = new char[strlen(p.val) + 1];
      strcpy(val, p.val);
    }
    return *this;
  }
  ~Pair() { // Destructor
    delete nm; // 0 value OK
    delete val;
  }
  // If you use this method outide this class, 
  // you're responsible for calling 'delete' on
  // the pointer that's returned:
  static char*
  decodeURLString(const char* URLstr) {
    int len = strlen(URLstr);
    char* result = new char[len + 1];
    memset(result, len + 1, 0);
    for(int i = 0, j = 0; i <= len; i++, j++) {
      if(URLstr[i] == '+')
        result[j] = ' ';
      else if(URLstr[i] == '%') {
        result[j] =
          translateHex(URLstr[i + 1]) * 16 +
          translateHex(URLstr[i + 2]);
        i += 2; // Move past hex code
      } else // An ordinary character
        result[j] = URLstr[i];
    }
    return result;
  }
  // Translate a single hex character; used by
  // decodeURLString():
  static char translateHex(char hex) {
    if(hex >= 'A')
      return (hex & 0xdf) - 'A' + 10;
    else
      return hex - '0';
  }
};
 
// Parses any CGI query and turns it
// into an STL vector of Pair objects:
class CGI_vector : public vector<Pair> {
  char* qry;
  const char* start; // Save starting position
  // Prevent assignment and copy-construction:
  void operator=(CGI_vector&);
  CGI_vector(CGI_vector&);
public:
  // const fields must be initialized in the C++
  // "Constructor initializer list":
  CGI_vector(char* query) :
      start(new char[strlen(query) + 1]) {
    qry = (char*)start; // Cast to non-const
    strcpy(qry, query);
    Pair p;
    while((p = nextPair()) != 0)
      push_back(p);
  }
  // Destructor:
  ~CGI_vector() { delete start; }
private:
  // Produces name-value pairs from the query 
  // string. Returns an empty Pair when there's 
  // no more query string left:
  Pair nextPair() {
    char* name = qry;
    if(name == 0 || *name == '')
      return Pair(); // End, return null Pair
    char* value = strchr(name, '=');
    if(value == 0)
      return Pair(); // Error, return null Pair
    // Null-terminate name, move value to start
    // of its set of characters:
    *value = '';
    value++;
    // Look for end of value, marked by '&':
    qry = strchr(value, '&');
    if(qry == 0) qry = ""; // Last pair found
    else {
      *qry = ''; // Terminate value string
      qry++; // Move to next pair
    }
    return Pair(name, value);
  }
}; ///:~ 

class Pair {
  string nm;
  string val;
public:
  Pair() { }
  Pair(char* name, char* value) {
    // Creates new memory:
    nm = decodeURLString(name);
    val = decodeURLString(value);
  }
  const char* name() const { return nm.c_str(); }
  const char* value() const { return val.c_str(); }
  // Test for "emptiness"
  bool empty() const {
    return (nm.length() == 0) || (val.length() == 0);
  }
  // Automatic type conversion for boolean test:
  operator bool() const {
    return (nm.length() != 0) && (val.length() != 0);
  }

//: Listmgr2.cpp
// CGI version of Listmgr.c in C++, which 
// extracts its input via the GET submission 
// from the associated applet. Also works as
// an ordinary CGI program with HTML forms.
#include <stdio.h>
#include "CGITools.h"
const char* dataFile = "list2.txt";
const char* notify = "[email protected]";
#undef DEBUG
 
// Similar code as before, except that it looks
// for the email name inside of '<>':
int inList(FILE* list, const char* emailName) {
  const int BSIZE = 255;
  char lbuf[BSIZE];
  char emname[BSIZE];
  // Put the email name in '<>' so there's no
  // possibility of a match within another name:
  sprintf(emname, "<%s>", emailName);
  // Go to the beginning of the list:
  fseek(list, 0, SEEK_SET);
  // Read each line in the list:
  while(fgets(lbuf, BSIZE, list)) {
    // Strip off the newline: 
    char * newline = strchr(lbuf, 'n');
    if(newline != 0)
      *newline = '';
    if(strstr(lbuf, emname) != 0)
      return 1;
  }
  return 0;
}
 
void main() {
  // You MUST print this out, otherwise the 
  // server will not send the response:
  printf("Content-type: text/plainnn");
  FILE* list = fopen(dataFile, "a+t");
  if(list == 0) {
    printf("error: could not open database. ");
    printf("Notify %s", notify);
    return;
  }
  // For a CGI "GET," the server puts the data
  // in the environment variable QUERY_STRING:
  CGI_vector query(getenv("QUERY_STRING"));
  #if defined(DEBUG)
  // Test: dump all names and values
  for(int i = 0; i < query.size(); i++) {
    printf("query[%d].name() = [%s], ",
      i, query[i].name());
    printf("query[%d].value() = [%s]n",
      i, query[i].value());
  }
  #endif(DEBUG)
  Pair name = query[0];
  Pair email = query[1];
  if(name.empty() || email.empty()) {
    printf("error: null name or email");
    return;
  }
  if(inList(list, email.value())) {
    printf("Already in list: %s", email.value());
    return;
  }
  // It's not in the list, add it:
  fseek(list, 0, SEEK_END);
  fprintf(list, "%s <%s>;n",
    name.value(), email.value());
  fflush(list);
  fclose(list);
  printf("%s <%s> added to listn",
    name.value(), email.value());
} ///:~ 

//: POSTtest.cpp
// CGI_vector works as easily with POST as it
// does with GET. Written in "pure" C++.
#include <iostream.h>
#include "CGITools.h"
 
void main() {
  cout << "Content-type: text/plainn" << endl;
  // For a CGI "POST," the server puts the length
  // of the content string in the environment 
  // variable CONTENT_LENGTH:
  char* clen = getenv("CONTENT_LENGTH");
  if(clen == 0) {
    cout << "Zero CONTENT_LENGTH" << endl;
    return;
  }
  int len = atoi(clen);
  char* query_str = new char[len + 1];
  cin.read(query_str, len);
  query_str[len] = '';
  CGI_vector query(query_str);
  // Test: dump all names and values
  for(int i = 0; i < query.size(); i++)
    cout << "query[" << i << "].name() = [" <<
      query[i].name() << "], " <<
      "query[" << i << "].value() = [" <<
      query[i].value() << "]" << endl;
  delete query_str; // Release storage
} ///:~ 

<HTML>
<HEAD>
<META CONTENT="text/html">
<TITLE>A test of standard HTML POST</TITLE>
</HEAD>
Test, uses standard html POST
<Form method="POST" ACTION="/cgi-bin/POSTtest">
<P>Field1: <INPUT TYPE = "text" NAME = "Field1"
VALUE = "" size = "40"></p>
<P>Field2: <INPUT TYPE = "text" NAME = "Field2"
VALUE = "" size = "40"></p>
<P>Field3: <INPUT TYPE = "text" NAME = "Field3"
VALUE = "" size = "40"></p>
<P>Field4: <INPUT TYPE = "text" NAME = "Field4"
VALUE = "" size = "40"></p>
<P>Field5: <INPUT TYPE = "text" NAME = "Field5"
VALUE = "" size = "40"></p>
<P>Field6: <INPUT TYPE = "text" NAME = "Field6"
VALUE = "" size = "40"></p>
<p><input type = "submit" name = "submit" > </p>
</Form>
</HTML>

//: POSTtest.java
// An applet that sends its data via a CGI POST
import java.awt.*;
import java.applet.*;
import java.net.*;
import java.io.*;
 
public class POSTtest extends Applet {
  final static int SIZE = 10;
  Button submit = new Button("Submit");
  TextField[] t = new TextField[SIZE];
  String query = "";
  Label l = new Label();
  TextArea ta = new TextArea(15, 60);
  public void init() {
    Panel p = new Panel();
    p.setLayout(new GridLayout(t.length + 2, 2));
    for(int i = 0; i < t.length; i++) {
      p.add(new Label(
        "Field " + i + "  ", Label.RIGHT));
      p.add(t[i] = new TextField(30));
    }
    p.add(l);
    p.add(submit);
    add("North", p);
    add("South", ta);
  }
  public boolean action (Event evt, Object arg) {
    if(evt.target.equals(submit)) {
      query = "";
      ta.setText("");
      // Encode the query from the field data:
      for(int i = 0; i < t.length; i++)
         query += "Field" + i + "=" +
           URLEncoder.encode(
             t[i].getText().trim()) +
           "&";
      query += "submit=Submit";
      // Send the name using CGI's POST process:
      try {
        URL u = new URL(
          getDocumentBase(), "cgi-bin/POSTtest");
        URLConnection urlc = u.openConnection();
        urlc.setDoOutput(true);
        urlc.setDoInput(true);
        urlc.setAllowUserInteraction(false);
        DataOutputStream server =
          new DataOutputStream(
            urlc.getOutputStream());
        // Send the data
        server.writeBytes(query);
        server.close();
        // Read and display the response. You
        // cannot use 
        // getAppletContext().showDocument(u);
        // to display the results as a Web page!
        DataInputStream in =
          new DataInputStream(
            urlc.getInputStream());
        String s;
        while((s = in.readLine()) != null) {
          ta.appendText(s + "n");
        }
        in.close();
      }
      catch (Exception e) {
        l.setText(e.toString());
      }
    }
    else return super.action(evt, arg);
    return true;
  }
} ///:~