Android Room: @Ignore vs Transient

Question

Are those two interchangable in context of Room database entity, or, if not, what are the differences between them?

Solution 1

@Ignore is a Room-specific annotation, saying that Room should ignore that field or method.

transient is a Java construct, indicating that this field should not be serialized in standard Java serialization. Room happens to treat this similarly to @Ignore by default. Mostly, that is there for cases where you are inheriting from some class that happens to use transient and you do not control that class (e.g., it is from a library).

For your own code, if you are not using Java serialization, I recommend sticking with @Ignore for the fields. transient is not an available keyword for a method, so to tell Room to ignore certain constructors, you have no choice but to use @Ignore.

Solution 2

Adding to CommonsWare's answer

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transient is not good option for ignoring fields for Room as CommonsWare answered. It will create blocker when same modal is being used to parse data from server and store into database.

Let's assume you have a modal class MyModal.java as below

public static class MyModal {

    @SerializedName(“intField”)
    public int intField;
    @SerializedName(“strField”)
    public String strField;
    @SerializedName(“booleanField”)
    public boolean booleanField;
}

If you want to NOT SAVE booleanField into database, and if you modified that field as

1. transient : It will ignore this field while saving into database, BUT it will also ignore this field while parsing data which comes from server.
2. @Ignore : It will only ignore this field while inserting data into database, but this field will participate into json parsing.