Issue # 78 | Feature: Add Email Contact Form Function for Java

(appwrite#78)

java/email-contact-form/.gitignore

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+# Compiled class file
+*.class
+
+# Log file
+*.log
+
+# BlueJ files
+*.ctxt
+
+# Mobile Tools for Java (J2ME)
+.mtj.tmp/
+
+# Package Files #
+*.jar
+*.war
+*.nar
+*.ear
+*.zip
+*.tar.gz
+*.rar
+
+# virtual machine crash logs, see http://www.java.com/en/download/help/error_hotspot.xml
+hs_err_pid*
+replay_pid*
+# Ignore Gradle project-specific cache directory
+.gradle
+
+# Ignore Gradle build output directory
+build

java/email-contact-form/README.md

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+# 📬 JAVA Email Contact Form Function
+
+Sends an email with the contents of a HTML form.
+
+## 🧰 Usage
+
+### GET /
+
+HTML forms for interacting with the function.
+
+### POST /
+
+Submit form data to send an email
+
+**Parameters**
+
+| Name   | Description                       | Location   | Type   | Sample Value                     |
+| ------ | --------------------------------- | ---------- | ------ | -------------------------------- |
+| \_next | URL for redirect after submission | Form Param | String | `https://mywebapp.org/success`   |
+| \*     | Any form values to send in email  | Form Param | String | `Hey, I'd like to get in touch!` |
+
+**Response**
+
+Sample `200` Response:
+
+```text
+Location: https://mywebapp.org/success
+```
+
+Sample `400` Response:
+
+```text
+Location: https://mywebapp.org/referer?error=Error+Description
+```
+
+## ⚙️ Configuration
+
+| Setting           | Value           |
+| ----------------- | --------------- |
+| Runtime           | Java (17)     |
+| Entrypoint        | `src/Main.java`   |
+| Permissions       | `any`           |
+| Timeout (Seconds) | 15              |
+
+## 🔒 Environment Variables
+
+### SMTP_HOST
+
+The address of your SMTP server. Many STMP providers will provide this information in their documentation. Some popular providers include: Mailgun, SendGrid, and Gmail.
+
+| Question     | Answer             |
+| ------------ | ------------------ |
+| Required     | Yes                |
+| Sample Value | `smtp.mailgun.org` |
+
+### SMTP_PORT
+
+The port of your STMP server. Commnly used ports include `25`, `465`, and `587`.
+
+| Question     | Answer |
+| ------------ | ------ |
+| Required     | Yes    |
+| Sample Value | `25`   |
+
+### SMTP_USERNAME
+
+The username for your SMTP server. This is commonly your email address.
+
+| Question     | Answer                  |
+| ------------ | ----------------------- |
+| Required     | Yes                     |
+| Sample Value | `no-reply@mywebapp.org` |
+
+### SMTP_PASSWORD
+
+The password for your SMTP server.
+
+| Question     | Answer                |
+| ------------ | --------------------- |
+| Required     | Yes                   |
+| Sample Value | `5up3r5tr0ngP4ssw0rd` |
+
+### SUBMIT_EMAIL
+
+The email address to send form submissions to.
+
+| Question     | Answer            |
+| ------------ | ----------------- |
+| Required     | Yes               |
+| Sample Value | `me@mywebapp.org` |
+
+### ALLOWED_ORIGINS
+
+An optional comma-separated list of allowed origins for CORS (defaults to `*`). This is an important security measure to prevent malicious users from abusing your function.
+
+| Question      | Answer                                                              |
+| ------------- | ------------------------------------------------------------------- |
+| Required      | No                                                                  |
+| Sample Value  | `https://mywebapp.org,https://mywebapp.com`                         |
+| Documentation | [MDN: CORS](https://developer.mozilla.org/en-US/docs/Web/HTTP/CORS) |

java/email-contact-form/deps.gradle

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+dependencies {
+    implementation 'io.appwrite:sdk-for-kotlin:4.0.0'
+    implementation 'com.sun.mail:jakarta.mail:2.0.0'
+}

java/email-contact-form/src/Cors.java

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+package io.openruntimes.java.src;
+
+import io.openruntimes.java.RuntimeContext;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.HashMap;
+import java.lang.*;
+
+
+public class Cors {
+
+    /*
+     * Returns true if the origin is allowed to make requests to this endpoint
+     *
+     * Parameters:
+     *   req: Request object
+     *
+     * Returns:
+     *   (boolean): True if the origin is allowed, False otherwise
+     */
+    public static boolean isOriginPermitted(RuntimeContext context) {
+        String allowedOrigins = System.getenv("ALLOWED_ORIGINS");
+        if (allowedOrigins == null || allowedOrigins.equals("*")) {
+            return true;
+        }
+
+        List<String> allowedOriginsList = Arrays.asList(allowedOrigins.split(","));
+        String originHeader = context.getReq().getHeaders().get("Origin");
+        return originHeader != null && allowedOriginsList.contains(originHeader);
+    }
+
+    /*
+     * Returns the CORS headers for the request
+     *
+     * Parameters:
+     *   req: Request object
+     *
+     * Returns:
+     *   (Map<String, String>): CORS headers
+     */
+    public static Map<String, String> getCorsHeaders(RuntimeContext context) {
+        if (!context.getReq().getHeaders().containsKey("origin")) {
+            return new HashMap<>();
+        }
+
+        String allowedOrigins = System.getenv("ALLOWED_ORIGINS");
+        if (allowedOrigins == null || allowedOrigins.equals("*")) {
+            return new HashMap<>(Map.of("Access-Control-Allow-Origin", "*"));
+        }
+
+        String originHeader = context.getReq().getHeaders().get("origin");
+        return new HashMap<>(Map.of("Access-Control-Allow-Origin", originHeader));
+    }
+}

java/email-contact-form/src/ErrorCode.java

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+package io.openruntimes.java.src;
+
+public class ErrorCode {
+    public static final String INVALID_REQUEST = "invalid-request";
+    public static final String MISSING_FORM_FIELDS = "missing-form-fields";
+    public static final String SERVER_ERROR = "server-error";
+}

java/email-contact-form/src/Main.java

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+package io.openruntimes.java.src;
+
+import io.openruntimes.java.RuntimeContext;
+import io.openruntimes.java.RuntimeOutput;
+import java.util.Map;
+import java.util.List;
+import java.util.HashMap;
+import java.util.Arrays;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.lang.*;
+import io.appwrite.Client;
+import jakarta.mail.MessagingException;
+
+
+public class Main {
+
+    public RuntimeOutput main(RuntimeContext context) throws Exception {
+
+        List<String> requiredEnvVariables = Arrays.asList(
+                "SUBMIT_EMAIL",
+                "SMTP_HOST",
+                "SMTP_USERNAME",
+                "SMTP_PASSWORD"
+        );
+
+        Utils.throwIfMissing(System.getenv(), requiredEnvVariables);
+        if (System.getenv("ALLOWED_ORIGINS").equals("*")) {
+            context.log("WARNING: Allowing requests from any origin - this is a security risk!");
+        }
+
+        if (context.getReq().getMethod().equals("GET")) {
+            return context.getRes().send(
+                    Utils.getHtmlContent("index.html"),
+                    200,
+                    Map.of("content-type", "text/html")
+            );
+        }
+
+
+        if(!context.getReq().getHeaders().get("content-type").equals("application/x-www-form-urlencoded")){
+            context.error("Incorrect content type");
+            String referer = context.getReq().getHeaders().get("referer");
+            String errorCode = ErrorCode.INVALID_REQUEST;
+            return context.getRes().redirect(
+                    String.format("%s?code=%s", referer, errorCode)
+            );
+        }
+
+        if(!Cors.isOriginPermitted(context)){
+            context.error("Origin not permitted");
+            String referer = context.getReq().getHeaders().get("referer");
+            String errorCode = ErrorCode.INVALID_REQUEST;
+            return context.getRes().redirect(
+                    String.format("%s?code=%s", referer, errorCode)
+            );
+        }
+
+        Map<String, List<String>> formData = new HashMap<>();
+        String body = (String) context.getReq().getBody();
+        String[] params = body.split("&");
+        for (String param : params) {
+            String[] keyValue = param.split("=");
+            String key = keyValue[0];
+            String value = keyValue[1];
+            if (!formData.containsKey(key)) {
+                formData.put(key, new ArrayList<>());
+            }
+            formData.get(key).add(value);
+        }
+
+        Map<String, String> form = new HashMap<>();
+        for (Map.Entry<String, List<String>> entry : formData.entrySet()) {
+            form.put(entry.getKey(), entry.getValue().get(0));
+        }
+
+        try {
+            Utils.throwIfMissing(form, Collections.singletonList("email"));
+        } catch (IllegalArgumentException ex) {
+            String referer = context.getReq().getHeaders().get("referer");
+            String errorCode = ErrorCode.MISSING_FORM_FIELDS;
+            return context.getRes().redirect(
+                    String.format("%s?code=%s", referer, errorCode),
+                    301,
+                    Cors.getCorsHeaders(context)
+            );
+        }
+
+
+        try {
+            Map<String, String> emailOptions = new HashMap<>();
+            emailOptions.put("from", System.getenv("SMTP_USERNAME"));
+            emailOptions.put("to", System.getenv("SUBMIT_EMAIL"));
+            emailOptions.put("subject", "New Contact Form Submission");
+            emailOptions.put("text", Utils.templateFormMessage(form));
+            Utils.sendEmail(emailOptions);
+        } catch (MessagingException ex) {
+            context.log("MessagingException: " + ex.getMessage());
+            String referer = context.getReq().getHeaders().get("referer");
+            String errorCode = ErrorCode.SERVER_ERROR;
+            return context.getRes().redirect(
+                    String.format("%s?code=%s", referer, errorCode),
+                    301,
+                    Cors.getCorsHeaders(context)
+            );
+        } catch (Exception ex) {
+            context.log("Exception: " + ex.getMessage());
+            String referer = context.getReq().getHeaders().get("referer");
+            String errorCode = ErrorCode.SERVER_ERROR;
+            return context.getRes().redirect(
+                    String.format("%s?code=%s", referer, errorCode),
+                    301,
+                    Cors.getCorsHeaders(context)
+            );
+        }
+
+        if (form.get("_next") == null || form.get("_next").isEmpty()) {
+            return context.getRes().send(
+                    Utils.getHtmlContent("success.html"),
+                    200,
+                    Map.of("content-type", "text/html; charset=utf-8")
+            );
+        }
+
+        return context.getRes().redirect(
+                Utils.joinURL(context.getReq().getHeaders().get("referer"), form.get("_next").substring(0,1)),
+                301,
+                Cors.getCorsHeaders(context)
+        );
+    }
+}