MyBatis Please allow extend base Enum handlers - change type access to protected

In both classes EnumTypeHandler and EnumOrdinalTypeHandler type defined as: private Class<E> type;: * https://github.com/mybatis/mybatis-3/blob/master/src/main/java/org/apache/ibatis/type/EnumTypeHandler.java#L28 * https://github.com/mybatis/mybatis-3/blob/master/src/main/java/org/apache/ibatis/type/EnumOrdinalTypeHandler.java#L28-L29

So in most cases I should copy/paste implementation if I want customize it. Please change it to protected

Comment From: hazendaz

If you need to extend it seems you might be replacing mostly what it does. If that is the case wouldn't it make more sense to write a new typehandler?

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On Sun, Jan 15, 2017 at 1:49 PM -0500, "Pavel Alexeev aka Pahan-Hubbitus" notifications@github.comamp#110;amp#111;amp#116;amp#105;amp#102;amp#105;amp#99;amp#97;amp#116;amp#105;amp#111;amp#110;amp#115;amp#64;amp#103;amp#105;amp#116;amp#104;amp#117;amp#98;amp#46;amp#99;amp#111;amp#109; wrote:

In both classes EnumTypeHandler and EnumOrdinalTypeHandler type defined as: private Class type;:

• https://github.com/mybatis/mybatis-3/blob/master/src/main/java/org/apache/ibatis/type/EnumTypeHandler.java#L28
• https://github.com/mybatis/mybatis-3/blob/master/src/main/java/org/apache/ibatis/type/EnumOrdinalTypeHandler.java#L28-L29

So in most cases I should copy/paste implementation if I want customize it. Please change it to protected

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Comment From: harawata

I agree with @hazendaz . Please let us know if we misunderstood your point.

Comment From: Hubbitus

My intention was to generalize idea from http://eminmamedov.org/?p=313 (sorry on Russian). But intention was to construct Enum just by reusing Jackson annotation @JsonCreator and do not register different type for any Enum, but have universal one.

Unfortunately EnumTypeHandler has private type field, so we can't just extend it and mostly copy/paste

Now prototype implemented exactly as you said: public class EnumJsonCreatorAnnotationTypeHandler<E extends Enum<E>> extends BaseTypeHandler<E> { but on my mind 80% is just copy/paste of EnumTypeHandler code instead of extending just on differences.

Comment From: harawata

@Hubbitus ,

Could you post both implementations of your EnumJsonCreatorAnnotationTypeHandler ?

• Current implementation.
• The ideal implementation when the modifier of EnumTypeHandler.type is protected.

I am not sure how they can be so different.

Comment From: Hubbitus

@harawata sorry for the long delay. My current implementation:

public class EnumJsonCreatorAnnotationTypeHandler<E extends Enum<E>> extends BaseTypeHandler<E> {
    private Class<E> type;

    /**
     * Full copy/paste from {@see EnumTypeHandler}. See https://github.com/mybatis/mybatis-3/issues/898
     */
    public EnumJsonCreatorAnnotationTypeHandler(Class<E> type) {
        if (type == null) {
            throw new IllegalArgumentException("Type argument cannot be null");
        }
        this.type = type;
    }

    /**
     * Full copy/paste from {@see EnumTypeHandler}. See https://github.com/mybatis/mybatis-3/issues/898
     */
    @Override
    public void setNonNullParameter(PreparedStatement ps, int i, E parameter, JdbcType jdbcType) throws SQLException {

        if (jdbcType == null) {
            ps.setString(i, parameter.name());
        } else {
            ps.setObject(i, parameter.name(), jdbcType.TYPE_CODE); // see r3589
        }
    }

    @Override
    public E getNullableResult(ResultSet rs, String columnName) throws SQLException {
        return enumFromDbValue(rs.getString(columnName));
    }

    @Override
    public E getNullableResult(ResultSet rs, int columnIndex) throws SQLException {
        return enumFromDbValue(rs.getString(columnIndex));
    }

    @Override
    public E getNullableResult(CallableStatement cs, int columnIndex) throws SQLException {
        return enumFromDbValue(cs.getString(columnIndex));
    }

    private E enumFromDbValue(String str){
        try {
            return str == null ? null : EnumUtils.enumFromValue(type, str);
        } catch (IOException e) {
            e.printStackTrace();
        }
        return null;
    }
}

So, I would like to remove unnecessary code copy pasting for the first two methods.

Comment From: harawata

Thanks for the update, @Hubbitus ,

Even if we change the access modifier to protected, you still need to define the constructor, so it does not make much difference. Extending the BaseTypeHandler is the right implementation.