Path to Firebase Admin Key in Java servlet

问题

I keep getting a

FileNotFoundException

when trying to initialize my app with Firebase saying it cannot find my adminsdk.json service key.

This is a specific error as I am trying to initialize Firebase in an Android Module Servlet.

Here is what my module project structure looks like:

And here is the code in my Serlvet that is trying to intialize FirebaseOptions:

FirebaseOptions options = null;
        try {
            options = new FirebaseOptions.Builder()
                    .setServiceAccount(new FileInputStream("leadsbackend\\src\\main\\webapp\\tt-social-firebase-adminsdk.json"))
                    .setDatabaseUrl(FIREBASE_DATABASE_URL)
                    .build();
        } catch (Exception e) {
            e.printStackTrace();
        }

And here is the error in the console:

java.io.FileNotFoundException: TTLeads\leadsbackend\src\main\webapp\tt-social-firebase-adminsdk.json (The system cannot find the path specified)
    at java.io.FileInputStream.open0(Native Method)
    at java.io.FileInputStream.open(FileInputStream.java:195)
    at java.io.FileInputStream.<init>(FileInputStream.java:138)
    at java.io.FileInputStream.<init>(FileInputStream.java:93)
    at com.nicholas.leadsbackend.LeadsServlet.sendToFirebase(LeadsServlet.java:63)
    at com.nicholas.leadsbackend.LeadsServlet.sendToBase(LeadsServlet.java:57)
    at com.nicholas.leadsbackend.LeadsServlet.doGet(LeadsServlet.java:37)

I am pretty sure I am not setting the URI correctly, but how would someone be able to reference a file in your package structure correctly? Any help is very appreciated.

Thanks in advance!

回答1:

I had cracked my head to enable reading of JSON key file in the system, when I stumbled on this article at: How to Use Facebook Account Kit to Authenticate Firebase App Users on Android. In this article, it explains in details to how to setup Firebase Admin SDK in a Cloud Endpoints module. I will summarize the steps here:

Place your serviceAccountKey.json in your apps' WEB-INF folder.

Insert this in your appengineweb.xml:

<resource-files>
    <include path="/**.json" />
</resource-files>

Define a class somewhere like the one below. Have a seperate init() method compulsorily:

public class FirebaseService {

public static void init() {
    try {
        FileInputStream serviceAccount = new FileInputStream(new File("WEB-INF/serviceAccountKey.json"));
        FirebaseOptions options = new FirebaseOptions.Builder()
            .setCredential(FirebaseCredentials.fromCertificate(serviceAccount))
            .setDatabaseUrl("https://[YOUR_APP_NAME].firebaseio.com/")
            .build();
        FirebaseApp.initializeApp(options);
        System.out.print("In Firebase Init module...!!");
    } catch(FileNotFoundException ignored) {}
}

Invoke this method in any of the static{} code in any of the Endpoints defined by you. For example:
```
static {
    ObjectifyService.register(FCMTokenMap.class);
    FirebaseService.init();
}
```
1. You can invoke other Firebase methods which involve Database, FCM, etc from anywhere..!

回答2:

I have resolved this issue like so:

I needed to place the .json file in my WEB-INF folder, and then user ServletContext to grab the resource as a stream, here is my example:

        FirebaseOptions options = null;
        ServletContext ctx = getServletContext();
        InputStream in = ctx.getResourceAsStream("/WEB-INF/tt-social-firebase-adminsdk.json");
        try {
            options = new FirebaseOptions.Builder()
                    .setServiceAccount(in)
                    .setDatabaseUrl(FIREBASE_DATABASE_URL)
                    .build();
        } catch (Exception e) {
            e.printStackTrace();
        }

That resolved all issues I was having accessing the file. Hope this helps someone else.

来源：https://stackoverflow.com/questions/41253548/path-to-firebase-admin-key-in-java-servlet

标签

java

android

servlets

firebase

firebase-realtime-database