How to create a table with a two or more foreign keys using Android Room?

Question

According the entity-relationship model, the relationship between tbl_post and tbl_category could be specified using Room Persistency Libr

Answer 1

TblCategory.java

@Entity
class TblCategory {
    @PrimaryKey
    @ColumnInfo(name="cat_id")
    public String id;

    @ColumnInfo(name = "cat_name")
    public String name;
}

TblPost.java (It is missing the foreign key reference but it is not important for the case)

@Entity
class TblPost {
    @PrimaryKey
    @ColumnInfo(name="post_id")
    public String id;

    public String title, content, create_time, author_id;
}

TblPostCategory.java

@Entity(foreignKeys = {
    @ForeignKey(
        entity = TblPost.class,
        parentColumns = "post_id",
        childColumns = "tbl_post_id"
    ),
    @ForeignKey(
        entity = TblCategory.class,
        parentColumns = "cat_id",
        childColumns = "tbl_category_id"
    )
})
class TblPostCategory {
    @PrimaryKey
    @ColumnInfo(name="tbl_post_id")
    public String id;

    @ColumnInfo(name = "tbl_category_id")
    public String categoryId;
}