Java-如何从Google Cloud Datastore删除实体

Question

Architecture: I have a web application from where I'm interacting with the Datastore and a client (raspberry pi) which is calling methods from the web application using Google Cloud Endpoints.

I have to add that I'm not very familiar with web applications and I assume that something's wrong with the setConsumed() method because I can see the call of /create in the app engine dashboard but there's no entry for /setConsumed.

I'm able to add entities to the Datastore using objectify:

//client method
private static void sendSensorData(long index, String serialNumber) throws IOException {
    SensorData data = new SensorData();
    data.setId(index+1);
    data.setSerialNumber(serialNumber);
    sensor.create(data).execute();
}

//api method in the web application
@ApiMethod(name = "create", httpMethod = "post")
public SensorData create(SensorData data, User user) {
    // check if user is authenticated and authorized
    if (user == null) {
        log.warning("User is not authenticated");
        System.out.println("Trying to authenticate user...");
        createUser(user);
        // throw new RuntimeException("Authentication required!");
    } else if (!Constants.EMAIL_ADDRESS.equals(user.getEmail())) {

        log.warning("User is not authorised, email: " + user.getEmail());
        throw new RuntimeException("Not authorised!");
    }
    data.save();

    return data;
}

//method in entity class SensorData
public Key<SensorData> save() {
    return ofy().save().entity(this).now();
}

However, I'm not able to delete an entity from the datastore using the following code.

EDIT: There are many logs of the create-request in Stackdriver Logging, but none of setConsumed() . So it seems like the calls don't even reach the API although both methods are in the same class.

EDIT 2: The entity gets removed when I invoke the method from the Powershell so the problem is most likely on client side.

//client method
private static void removeSensorData(long index) throws IOException {
    sensor.setConsumed(index+1);
}

//api method in the web application
@ApiMethod(name = "setConsumed", httpMethod = "put")
public void setConsumed(@Named("id") Long id, User user) {
    // check if user is authenticated and authorized
    if (user == null) {
        log.warning("User is not authenticated");
        System.out.println("Trying to authenticate user...");
        createUser(user);
        // throw new RuntimeException("Authentication required!");
    } else if (!Constants.EMAIL_ADDRESS.equals(user.getEmail())) {

        log.warning("User is not authorised, email: " + user.getEmail());
        throw new RuntimeException("Not authorised!");
    }

    Key serialKey = KeyFactory.createKey("SensorData", id);
    datastore.delete(serialKey);
}

Answer 1

I was able to solve it by myself finally!

The problem was just related to the data type of the index used for removeSensorData(long index) which came out of a for-loop and therefore was an Integer instead of a long.

Answer 2

This is what I follow to delete an entity from datastore.

public boolean deleteEntity(String propertyValue) {
    String entityName = "YOUR_ENTITY_NAME";
    String gql = "SELECT * FROM "+entityName +" WHERE property= "+propertyValue+"";
    Query<Entity> query = Query.newGqlQueryBuilder(Query.ResultType.ENTITY, gql)
            .setAllowLiteral(true).build();
    try{
        QueryResults<Entity> results = ds.run(query);           
        if (results.hasNext()) {
            Entity rs = results.next();             
            ds.delete(rs.getKey());
            return true;
        }
        return false;
    }catch(Exception e){
        logger.error(e.getMessage());
        return false;
    }
}

If you don't want to use literals, you can also use binding as follows:

String gql = "SELECT * FROM "+entityName+" WHERE property1= @prop1 AND property2= @prop2";      
Query<Entity> query = Query.newGqlQueryBuilder(Query.ResultType.ENTITY, gql)
            .setBinding("prop1", propertyValue1)
            .setBinding("prop2", propertyValue2)
            .build();

Hope this helps.