Java Gson Exclude fields during serialization

Question

I have a ConfigInstance class which contains a password and a password_hash. Now I want to serialize the object using gson but exclude the password field.

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 */} } 

As you can see, I have tried using @Expose(serialize = false) but it doesn't seem to do anything. Also I already set the field to private since I figured that this would "override" the @Expose

but running following 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());     } } 

still results in the following file content without Errors:

{   "database_address": "127.0.0.1",   "database_port": 1521,   "database_user": "test",   "database_pass": "test1234",   "database_pass_hash": "B9FE2C011B59F0D0D383D70073E48A19" } 

So what am I doing wrong? I am pretty clueless right now and would appreciate any help since THIS doesn't seem to work.

Thanks in advance.

Answer 1

In order to get this result, you need to annotate all the fields with the @Expose:

public class ConfigInstance {      @Expose     public String database_address;     @Expose     public int database_port;     @Expose     public String database_user;      @Expose(serialize = false)     private String database_pass;     @Expose     public String database_pass_hash; 

And configure Gson to only expose fields that are annotated and ignore the rest as shown in the following:

Gson gson = new GsonBuilder().excludeFieldsWithoutExposeAnnotation().setPrettyPrinting().create(); 

Then, you'll get:

{   "database_address": "127.0.0.1",   "database_port": 1521,   "database_user": "test",   "database_pass_hash": "B9FE2C011B59F0D0D383D70073E48A19" } 

Also, when deserialising the string you'll still have the password attribute as well.

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Still, you have the possibility to configure a Gson Serializer to accomplish this.

Answer 2

This is another way.

serialization:

Gson gson = new GsonBuilder()             .addSerializationExclusionStrategy(new ExclusionStrategy() {                 @Override                 public boolean shouldSkipField(FieldAttributes f) {                     return f.getName().toLowerCase().contains("fieldName");                 }                  @Override                 public boolean shouldSkipClass(Class<?> aClass) {                     return false;                 }             })             .create(); 

deserialization:

Gson gson = new GsonBuilder()             .addDeserializationExclusionStrategy(new ExclusionStrategy() {                 @Override                 public boolean shouldSkipField(FieldAttributes f) {                     return f.getName().toLowerCase().contains("fieldName");                 }                  @Override                 public boolean shouldSkipClass(Class<?> aClass) {                     return false;                 }             })             .create();