title: HTTP ERROR 503 Service Unavailable in spring boot project
body: <p>I had a spring-boot project which is connected with the google cloud MySQL database. I need to deploy this project as a service in the google cloud app engine. Once I deploy this project It doesn't show any errors and deploys successfully. But once I run the service It gives this error shown in the below screenshot.</p>
  
  <p><strong>Error message,</strong></p>
  
  <p><a href="https://i.stack.imgur.com/LhT7l.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/LhT7l.png" alt="enter image description here"></a></p>
  
  <p><strong>This is the screenshot of my project structure,</strong></p>
  
  <p><a href="https://i.stack.imgur.com/5qjjU.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/5qjjU.png" alt="enter image description here"></a></p>
  
  <p><strong>pom.xml</strong></p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd"&gt;
      &lt;modelVersion&gt;4.0.0&lt;/modelVersion&gt;
      &lt;parent&gt;
          &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
          &lt;artifactId&gt;spring-boot-starter-parent&lt;/artifactId&gt;
          &lt;version&gt;2.2.6.RELEASE&lt;/version&gt;
          &lt;relativePath/&gt; &lt;!-- lookup parent from repository --&gt;
      &lt;/parent&gt;
      &lt;groupId&gt;com.sdgsix&lt;/groupId&gt;
      &lt;artifactId&gt;Mealize&lt;/artifactId&gt;
      &lt;version&gt;0.0.1-SNAPSHOT&lt;/version&gt;
      &lt;packaging&gt;war&lt;/packaging&gt;
      &lt;name&gt;Mealize&lt;/name&gt;
      &lt;description&gt;Back-end for the Mealize food recommendation mobile app&lt;/description&gt;
  
      &lt;properties&gt;
          &lt;java.version&gt;1.8&lt;/java.version&gt;
      &lt;/properties&gt;
  
      &lt;dependencies&gt;
          &lt;dependency&gt;
              &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
              &lt;artifactId&gt;spring-boot-starter-web&lt;/artifactId&gt;
          &lt;/dependency&gt;
  
          &lt;dependency&gt;
              &lt;groupId&gt;javax.servlet&lt;/groupId&gt;
              &lt;artifactId&gt;javax.servlet-api&lt;/artifactId&gt;
              &lt;version&gt;3.1.0&lt;/version&gt;
              &lt;scope&gt;provided&lt;/scope&gt;
          &lt;/dependency&gt;
  
          &lt;dependency&gt;
              &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
              &lt;artifactId&gt;spring-boot-starter-data-jpa&lt;/artifactId&gt;
          &lt;/dependency&gt;
  
          &lt;!-- Base64 algorithm dependencies --&gt;
          &lt;dependency&gt;
              &lt;groupId&gt;net.iharder&lt;/groupId&gt;
              &lt;artifactId&gt;base64&lt;/artifactId&gt;
              &lt;version&gt;2.3.8&lt;/version&gt;
          &lt;/dependency&gt;
  
          &lt;!-- https://mvnrepository.com/artifact/com.codetaco/calendar --&gt;
          &lt;dependency&gt;
              &lt;groupId&gt;com.codetaco&lt;/groupId&gt;
              &lt;artifactId&gt;calendar&lt;/artifactId&gt;
              &lt;version&gt;3.0.2&lt;/version&gt;
          &lt;/dependency&gt;
  
  
          &lt;dependency&gt;
              &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
              &lt;artifactId&gt;spring-boot-starter-test&lt;/artifactId&gt;
              &lt;scope&gt;test&lt;/scope&gt;
              &lt;exclusions&gt;
                  &lt;exclusion&gt;
                      &lt;groupId&gt;org.junit.vintage&lt;/groupId&gt;
                      &lt;artifactId&gt;junit-vintage-engine&lt;/artifactId&gt;
                  &lt;/exclusion&gt;
              &lt;/exclusions&gt;
          &lt;/dependency&gt;
      &lt;/dependencies&gt;
  
      &lt;build&gt;
          &lt;plugins&gt;
              &lt;plugin&gt;
                  &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
                  &lt;artifactId&gt;spring-boot-maven-plugin&lt;/artifactId&gt;
              &lt;/plugin&gt;
              &lt;plugin&gt;
                  &lt;groupId&gt;com.google.cloud.tools&lt;/groupId&gt;
                  &lt;artifactId&gt;appengine-maven-plugin&lt;/artifactId&gt;
                  &lt;version&gt;1.3.1&lt;/version&gt;
              &lt;/plugin&gt;
              &lt;plugin&gt;
                  &lt;groupId&gt;org.apache.maven.plugins&lt;/groupId&gt;
                  &lt;artifactId&gt;maven-surefire-plugin&lt;/artifactId&gt;
                  &lt;version&gt;2.19.1&lt;/version&gt;
              &lt;/plugin&gt;
          &lt;/plugins&gt;
      &lt;/build&gt;
  
  &lt;/project&gt;
  </code></pre>