title: Java Gson Exclude fields during serialization
body: <p>I have a <code>ConfigInstance</code> class which contains a <code>password</code> and a <code>password_hash</code>.
  Now I want to serialize the object using gson but exclude the <code>password</code> field.</p>
  
  <pre><code>public class ConfigInstance {
      public String database_address;
      public int database_port;
      public String database_user;
  
      @Expose(serialize = false)
      private String database_pass;
      public String database_pass_hash;
  
      public String GetPass() { return database_pass; }
  
      public void Encrypt() { /* Creates the hash before serializing*/ }
  
      public void Decrypt() { /* Creates the password after deserializing */}
  }
  </code></pre>
  
  <p>As you can see, I have tried using <code>@Expose(serialize = false)</code> but it doesn't seem to do anything. Also I already set the field to private since I figured that this would "override" the <code>@Expose</code></p>
  
  <p>but running following code:</p>
  
  <pre><code>private void toFile(File file, ConfigInstance map) {
      map.Encrypt();
      Gson gson = new GsonBuilder().setPrettyPrinting().create();
      String jsonConfig = gson.toJson(map);
      FileWriter writer;
      try {
          writer = new FileWriter(file);
          writer.write(jsonConfig);
          writer.flush();
          writer.close();
      } catch (IOException e) {
          System.out.println("Error exporting config: " + e.toString());
      }
  }
  </code></pre>
  
  <p>still results in the following file content without Errors:</p>
  
  <pre><code>{
    "database_address": "127.0.0.1",
    "database_port": 1521,
    "database_user": "test",
    "database_pass": "test1234",
    "database_pass_hash": "B9FE2C011B59F0D0D383D70073E48A19"
  }
  </code></pre>
  
  <p>So what am I doing wrong? I am pretty clueless right now and would appreciate any help since <a href="http://www.javacreed.com/gson-annotations-example/" rel="noreferrer">THIS</a> doesn't seem to work.</p>
  
  <p>Thanks in advance.</p>