Google Calendar API V3 Java: Unable to use 'primary' for Calendars:get

Question

I'm very new to the Google Calendar V3 Java API. I'm developing in Java, using Eclipse. So far, I have succeeded in:

1. Getting the CalendarList summaries of all the different calendars inside a particular Google account
2. Getting the CalendarList summary of just one of the calendars inside a particular Google account, using the Calendar ID as an identifier.

Now, I would like to explore Calendars instead of CalendarList. I tried implementing the Calendars get method. However, I am facing a problem.

Google's tutorial states this as an example code:

Calendar calendar = service.calendars().get('primary').execute();
System.out.println(calendar.getSummary());

However, Eclipse highlights the 'primary' and says that it is an "Invalid Character Constant".

I tried changing it into a string "primary" instead, and Eclipse highlights the entire line, saying that there is a type mismatch.

I am very unsure what is really expected from the 'primary' array of strings given in Google's tutorial. Am I supposed to replace it with the calendar ID of the primary calendar? I tried that, both as a string and as an array of characters, but I keep on getting compilation errors from Eclipse.

Here is my code used:

public static void getCalendarSummary(String calendarID, Calendar service) throws IOException{ 
    Calendar calendar = service.calendars().get("primary").execute();
    System.out.println(calendar.getSummary());
}

Would anyone be able to enlighten me as to what I'm doing wrong? I have searched all over the Google tutorial references, but failed to come to a conclusion. Thank you.

This is the link to Google's tutorial: https://developers.google.com/google-apps/calendar/v3/reference/calendars/get?hl=fr

Edit: After running the program, this is what I get. The first two methods work fine and deliver the right results. However, I get an error for the method in question - unresolved compilation problem - invalid character constant. Here's the entire response:

Go to the following address:
https://accounts.google.com/o/oauth2/auth?client_id=369332843116-gr8ct1guerlf1fudpgivfjv43h0oleip.apps.googleusercontent.com&redirect_uri=urn:ietf:wg:oauth:2.0:oob&response_type=code&scope=https://www.googleapis.com/auth/calendar
What is the 'code' url parameter?
4/LvuhiV9Qb_gzCgXmkveIw2kfbOFA.gtXwZ0hWA0QRcp7tdiljKKa1LV4tkQI
GooCal
ID: quolc4s8etou3ea1ca071ud9tk@group.calendar.google.com
Summary: DEADLINES
ID: u8jsu7vcrbh9okbj4tbs1nev74@group.calendar.google.com
Summary: Calendar 1
ID: gfof3i5u8pdn3esjk3mbmgiop8@group.calendar.google.com
Summary: LightUp
ID: i.*****@gmail.com
Summary: Personal Events
ID: w*****@gmail.com
Summary: w*****@gmail.com
ID: horiq2vgch2cprklf58ntdvhd8@group.calendar.google.com
Summary: Team A********** - Orbital Project
ID: 2h4du2sgsu1t5p2238j2mbk77k@group.calendar.google.com
Summary: TechTouch - GG Fix
ID: i357fqqhffrf1fa9udcbn9sikc@group.calendar.google.com
Summary: GooCal
ID: en.singapore#holiday@group.v.calendar.google.com
Summary: Holidays in Singapore
Exception in thread "main" java.lang.Error: Unresolved compilation problem: 
    Invalid character constant

    at SimpleCalendarTest.getCalendarSummary(SimpleCalendarTest.java:100)
    at SimpleCalendarTest.main(SimpleCalendarTest.java:81)

Here is my entire code, if it will help. :)

import java.io.IOException;
import java.util.Collections;
import java.util.Scanner;
import java.util.Set;

import com.google.api.client.auth.oauth2.AuthorizationCodeFlow;
import com.google.api.client.auth.oauth2.AuthorizationCodeRequestUrl;
import com.google.api.client.auth.oauth2.AuthorizationCodeTokenRequest;
import com.google.api.client.auth.oauth2.Credential;
import com.google.api.client.auth.oauth2.TokenResponse;
import com.google.api.client.googleapis.auth.oauth2.GoogleAuthorizationCodeFlow;
import com.google.api.client.http.HttpRequestInitializer;
import com.google.api.client.http.HttpTransport;
import com.google.api.client.http.javanet.NetHttpTransport;
import com.google.api.client.json.JsonFactory;
import com.google.api.client.json.jackson.JacksonFactory;
import com.google.api.services.calendar.Calendar;
import com.google.api.services.calendar.CalendarScopes;
import com.google.api.services.calendar.model.CalendarList;
import com.google.api.services.calendar.model.CalendarListEntry;
import com.google.api.services.calendar.model.*;


public class SimpleCalendarTest {
    public static void main(String[] args) throws IOException{
        //Two globals that will be used in each step.
        HttpTransport httpTransport = new NetHttpTransport();
        JsonFactory jsonFactory = new JacksonFactory();

        //Create the authorization code flow manager
        Set<String> scope = Collections.singleton(CalendarScopes.CALENDAR);
        String clientId = "xxxxxxx";
        String clientSecret = "xxxxxxx";

        //Use a factory pattern to create the code flow
        AuthorizationCodeFlow.Builder codeFlowBuilder = 
                new GoogleAuthorizationCodeFlow.Builder(
                        httpTransport, 
                        jsonFactory, 
                        clientId, 
                        clientSecret, 
                        scope
                );
        AuthorizationCodeFlow codeFlow = codeFlowBuilder.build();

        //set the code flow to use a dummy user
        //in a servlet, this could be the session id
        String userId = "ipeech";

        //"redirect" to the authentication url
        String redirectUri = "urn:ietf:wg:oauth:2.0:oob";
        AuthorizationCodeRequestUrl authorizationUrl = codeFlow.newAuthorizationUrl();
        authorizationUrl.setRedirectUri(redirectUri);
        System.out.println("Go to the following address:");
        System.out.println(authorizationUrl);

        //use the code that is returned as a url parameter
        //to request an authorization token
        System.out.println("What is the 'code' url parameter?");
        String code = new Scanner(System.in).nextLine();

        AuthorizationCodeTokenRequest tokenRequest = codeFlow.newTokenRequest(code);
        tokenRequest.setRedirectUri(redirectUri);
        TokenResponse tokenResponse = tokenRequest.execute();

        //Now, with the token and user id, we have credentials
        Credential credential = codeFlow.createAndStoreCredential(tokenResponse, userId);

        //Credentials may be used to initialize http requests
        HttpRequestInitializer initializer = credential;
        //and thus are used to initialize the calendar service
        Calendar.Builder serviceBuilder = new Calendar.Builder(
                httpTransport, jsonFactory, initializer);
        serviceBuilder.setApplicationName("GooCal");
        Calendar calendar = serviceBuilder.build();

        //get some data
        String calendarID = "xxxxxxxx@group.calendar.google.com";
        getCalendarListSummary(calendarID,calendar);
        getAllCalendarListSummary(calendar);
        getCalendarSummary(calendarID,calendar);
    }

    public static void getCalendarListSummary(String calendarID, Calendar calendar) throws IOException{
        CalendarListEntry calendarListEntry = calendar.calendarList().get(calendarID).execute();
        System.out.println(calendarListEntry.getSummary());
    }

    public static void getAllCalendarListSummary (Calendar calendar) throws IOException{
        Calendar.CalendarList.List listRequest = calendar.calendarList().list();
        CalendarList feed = listRequest.execute();
        for(CalendarListEntry entry:feed.getItems()){
            System.out.println("ID: " + entry.getId());
            System.out.println("Summary: " + entry.getSummary());
        }
    }


    public static void getCalendarSummary(String calendarID, Calendar service) throws IOException{ 
        Calendar calendar = service.calendars().get('primary').execute();
        System.out.println(calendar.getSummary());
    }
}

Thanks! :)

Edit 2: When I replace 'primary' with "primary", this is the error message I get.

What is the 'code' url parameter?
    4/LvuhiV9Qb_gzCgXmkveIw2kfbOFA.gtXwZ0hWA0QRcp7tdiljKKa1LV4tkQI
    GooCal
    ID: quolc4s8etou3ea1ca071ud9tk@group.calendar.google.com
    Summary: DEADLINES
    ID: u8jsu7vcrbh9okbj4tbs1nev74@group.calendar.google.com
    Summary: Calendar 1
    ID: gfof3i5u8pdn3esjk3mbmgiop8@group.calendar.google.com
    Summary: LightUp
    ID: i.*****@gmail.com
    Summary: Personal Events
    ID: w*****@gmail.com
    Summary: w*****@gmail.com
    ID: horiq2vgch2cprklf58ntdvhd8@group.calendar.google.com
    Summary: Team A********** - Orbital Project
    ID: 2h4du2sgsu1t5p2238j2mbk77k@group.calendar.google.com
    Summary: TechTouch - GG Fix
    ID: i357fqqhffrf1fa9udcbn9sikc@group.calendar.google.com
    Summary: GooCal
    ID: en.singapore#holiday@group.v.calendar.google.com
    Summary: Holidays in Singapore
Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
    Type mismatch: cannot convert from com.google.api.services.calendar.model.Calendar to com.google.api.services.calendar.Calendar
    The method getSummary() is undefined for the type Calendar

    at SimpleCalendarTest.getCalendarSummary(SimpleCalendarTest.java:100)
    at SimpleCalendarTest.main(SimpleCalendarTest.java:81)

It appears that there is a type mismatch. Thanks for your help!

Edit 3: Replacing import com.google.api.services.calendar.Calendar with com.google.api.services.calendar.model.Calendar causes other problems. Eclipse highlights that the code used to initialize the calendar service has a problem. Calendar.Builder cannot be resolved as a type.

Calendar.Builder serviceBuilder = new Calendar.Builder(
                httpTransport, jsonFactory, initializer);

When I run, I get this error.

Exception in thread "main" java.lang.Error: Unresolved compilation problems: 
    Calendar.Builder cannot be resolved to a type
    Calendar.Builder cannot be resolved to a type

    at SimpleCalendarTest.main(SimpleCalendarTest.java:73)

Thanks for your help!

Answer 1

将此导入com.google.api.services.calendar.Calendar替换为com.google.api.services.calendar.model.Calendar。

Answer 2

1. Use double quotes instead of single quotes around "primary" :) Single quotes are for chars, like 'a' in Java.
2. Read the error: "Type mismatch: cannot convert from com.google.api.services.calendar.model.Calendar to com.google.api.services.calendar.Calendar". These are two absolutely different classes (note the package names), "Calendar" is just part of class name.