[JAVA] Get holidays with the Google Calendar API

Article summary

--How to get holidays using Google Calendar API in Maven --You can use it by playing with the official sample code --Tokens are reset regularly

background

Since the Google Calendar API is famous, it's easy to find a way to use it, but I've had a little trouble with PHP and Python, so I'll write it for someone similar to me.

Purpose

Rewrite the official sample code for Maven to get holidays. A weak engineer who is a new graduate for half a year writes the contents in an easy-to-understand manner.

procedure

-Official sample Reference ――The repository I actually created is this

1. Create a Maven project (Refer to this)

--You should have a src folder and pom.xml in your project

$ mvn archetype:generate \
  -DarchetypeArtifactId=maven-archetype-quickstart \
  -DinteractiveMode=false \
  -DgroupId={com.ikeponias} \
  -DartifactId={google-calendar-sample}

2. Download the Credential file

-On the Official Sample page

1. Click "ENABLE GOOGLE CALENDAR API"

3. Copy the source

1. Rename the ʻApp.java file in src / maintoCalendarQuickstart.java`
2. Go to CalendarQuickstart.java Copy the contents of CalendarQuickstart.java in Official Sample.

4. Edit the source file

1. Add the package name to the first line of src / main / CalendarQuickstart.java (It depends on whether the folder hierarchy has been changed, but basically the groupId when it was first generated. I ampackage com.ikeponias; And add)
2. Change the argument passed to service.events (). List () in the main method of src / main / CalendarQuickstart.java from primary to [email protected]. (Because it is an API to get calendar events, your own event will appear if you do not do this, Reference)

5. Edit pom.xml

1. Add the following dependency

• google-api-client
• google-oauth-client-jetty
• google-api-services-calendar

2. Add ʻexec-maven-plugin to plugin`

--To call the main function from the command line --Specify java for goal --Specify the location of CalendarQuickstart.java for mainClass (com.ikeponias.CalendarQuickstart in my case)

Below is my example (junit is written when the project is created)

  <dependencies>
    <!-- https://mvnrepository.com/artifact/com.google.api-client/google-api-client -->
    <dependency>
      <groupId>com.google.api-client</groupId>
      <artifactId>google-api-client</artifactId>
      <version>1.26.0</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/com.google.oauth-client/google-oauth-client-jetty -->
    <dependency>
      <groupId>com.google.oauth-client</groupId>
      <artifactId>google-oauth-client-jetty</artifactId>
      <version>1.26.0</version>
    </dependency>
    <!-- https://mvnrepository.com/artifact/com.google.apis/google-api-services-calendar -->
    <dependency>
      <groupId>com.google.apis</groupId>
      <artifactId>google-api-services-calendar</artifactId>
      <version>v3-rev355-1.25.0</version>
    </dependency>

    <!--Should already exist when the project is created-->
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <!-- https://mvnrepository.com/artifact/org.codehaus.mojo/exec-maven-plugin -->
      <plugin>
        <groupId>org.codehaus.mojo</groupId>
        <artifactId>exec-maven-plugin</artifactId>
        <version>1.6.0</version>
        <executions>
          <execution>
            <goals>
              <goal>java</goal>
            </goals>
          </execution>
        </executions>
        <configuration>
          <mainClass>com.ikeponias.CalendarQuickstart</mainClass>
        </configuration>
      </plugin>
    </plugins>
  </build>

6. Run

1. Run mvn clean install in the terminal
2. Execute mvn exec: java
3. A list of 10 holidays after the execution date is output (read the source and official document for details)

I was addicted to

Write the points you are addicted to below

I get a 401 Unauthorized Error

com.google.api.client.auth.oauth2.TokenResponseException: 401 Unauthorized

Reason

Because the token has expired

Countermeasures

Delete the tokens folder and re-execute (it may be good to include a process to delete the tokens folder at the time of execution)

Events not found with No upcoming events found.

Reason

The argument passed to service.events (). List () in the main method of src / main / CalendarQuickstart.java is primary.

Countermeasures

Change primary to [email protected]