In fact, some settings for built-in aliases can be simplified

[YHHD]

We can see this picture. Both types, Character and Integer, provide two aliases. I think this is unnecessary.
We know that Java provides basic data types and wrapper types. In the design of built-in aliases, the aliases of basic data types are underlined in front to distinguish them from the aliases of wrapper types.

Why can't we unify them, delete the two aliases : integer and character, and only use int and char? Is this for compatibility?

[hazendaz]

Hi, I'm sure others can answer far better than me but can you point to the code as to where you think this is a problem? They are clearly different in general. Sure one is a wrapper, if its int and you want Integer, it requires wrapping/unwrapping which IMO I avoid by making sure to be explicit. I don't know if the internals are doing something based on that aspect, probably are but pointing to code would help.

Also if you could write markdown for images instead of images as no one can search on images.

[YHHD]

https://mybatis.org/mybatis-3/configuration.html#typealiases

Sorry, I didn’t give the source. I just think that there is no need to provide two aliases for the wrapper class Integer and Character. They can be optimized into a single alias, which is easy to remember and concise.

[YHHD]

like:

Alias	Mapped Type
_int	int
_char	char
int	Integer
char	Character

[YHHD]

public class TypeAliasRegistry {
    private final Map<String, Class<?>> typeAliases = new HashMap();

    public TypeAliasRegistry() {
        this.registerAlias("string", String.class);
        this.registerAlias("byte", Byte.class);
        this.registerAlias("char", Character.class);
        this.registerAlias("character", Character.class);
        this.registerAlias("long", Long.class);
        this.registerAlias("short", Short.class);
        this.registerAlias("int", Integer.class);
        this.registerAlias("integer", Integer.class);
        this.registerAlias("double", Double.class);
        this.registerAlias("float", Float.class);
        this.registerAlias("boolean", Boolean.class);
        this.registerAlias("byte[]", Byte[].class);
        this.registerAlias("char[]", Character[].class);
        this.registerAlias("character[]", Character[].class);
        this.registerAlias("long[]", Long[].class);
        this.registerAlias("short[]", Short[].class);
        this.registerAlias("int[]", Integer[].class);
        this.registerAlias("integer[]", Integer[].class);
        this.registerAlias("double[]", Double[].class);
        this.registerAlias("float[]", Float[].class);
        this.registerAlias("boolean[]", Boolean[].class);
        this.registerAlias("_byte", Byte.TYPE);
        this.registerAlias("_char", Character.TYPE);
        this.registerAlias("_character", Character.TYPE);
        this.registerAlias("_long", Long.TYPE);
        this.registerAlias("_short", Short.TYPE);
        this.registerAlias("_int", Integer.TYPE);
        this.registerAlias("_integer", Integer.TYPE);
        this.registerAlias("_double", Double.TYPE);
        this.registerAlias("_float", Float.TYPE);
        this.registerAlias("_boolean", Boolean.TYPE);
        this.registerAlias("_byte[]", byte[].class);
        this.registerAlias("_char[]", char[].class);
        this.registerAlias("_character[]", char[].class);
        this.registerAlias("_long[]", long[].class);
        this.registerAlias("_short[]", short[].class);
        this.registerAlias("_int[]", int[].class);
        this.registerAlias("_integer[]", int[].class);
        this.registerAlias("_double[]", double[].class);
        this.registerAlias("_float[]", float[].class);
        this.registerAlias("_boolean[]", boolean[].class);
        this.registerAlias("date", Date.class);
        this.registerAlias("decimal", BigDecimal.class);
        this.registerAlias("bigdecimal", BigDecimal.class);
        this.registerAlias("biginteger", BigInteger.class);
        this.registerAlias("object", Object.class);
        this.registerAlias("date[]", Date[].class);
        this.registerAlias("decimal[]", BigDecimal[].class);
        this.registerAlias("bigdecimal[]", BigDecimal[].class);
        this.registerAlias("biginteger[]", BigInteger[].class);
        this.registerAlias("object[]", Object[].class);
        this.registerAlias("map", Map.class);
        this.registerAlias("hashmap", HashMap.class);
        this.registerAlias("list", List.class);
        this.registerAlias("arraylist", ArrayList.class);
        this.registerAlias("collection", Collection.class);
        this.registerAlias("iterator", Iterator.class);
        this.registerAlias("ResultSet", ResultSet.class);
    }
 ……

This is where the built-in type aliases are added.

[hazendaz]

Thanks for adding additional information. I still think its needed but will let others comment.

[harawata]

Hello @YHHD ,

We won't remove existing aliases because it breaks backward compatibility.
Such a change is only justified when there is a security concern or it significantly improves performance (memory usage and/or speed), for example.