JTrans4mers

A Java tool to easily map an Object to an Enum.

This tool gives you the ability to convert an Object to an Enum value by applying a sequence of transformations without throwing any exception.

Requires JDK 1.8 or higher.

Installation

To add a dependency on JTrans4mers using Maven, use the following:

<dependency>
  <groupId>com.ekino.oss.converter</groupId>
  <artifactId>jtrans4mers</artifactId>
  <version>1.0</version>
</dependency>

Usage

Given the two following enumerations :

enum A {
    COMMON_VALUE,
    A_VALUE
}

enum B {
    COMMON_VALUE,
    B_VALUE
}

An Enum to another Enum value

Here is the simpliest way to convert an Enum value to another one :

// This converts A value to B value by their names
Optional<B> result = EnumConverter.convert(A.COMMON_VALUE, B.class); // result.get() : B.COMMON_VALUE

Optional<B> result = EnumConverter.convert(A.A_VALUE, B.class); // result : empty

You can also use the fluent way :

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;

Optional<B> result = to(B.class).convert(A.COMMON_VALUE); // result.get() : B.COMMON_VALUE

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;

Optional<B> result = to(B.class).convert(A.A_VALUE); // result : empty

An Object to an Enum value

This does not only apply on Enum input. An object can be used to match with the target enum name :

• Enum input will use the Enum.getName().
• Any other Object type input will use the Object.toString().

String input

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;

Optional<B> result = to(B.class).convert("COMMON_VALUE"); // result.get() : B.COMMON_VALUE

Object input

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;

Object input = new Object() {
    @Override
    public String toString() {
        return "COMMON_VALUE";
    }
};

Optional<B> result = to(B.class).convert(input); // result.get() : B.COMMON_VALUE

Null safe input

Optional<B> result = EnumConverter.convert(null, B.class); // result : empty

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;

Optional<B> result = to(B.class).convert(null); // result : empty

Transformers

You can apply custom transformation(s) and fallback(s). These are simple Java Function.

How to use a custom transformer :

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.convert;

Function<String, B> transformer = input -> "B".equals(input) ? B.B_VALUE : null;

Optional<B> result = convert("B", transformer); // result.get() : B.B_VALUE

Or a sequence of transformers :

import static java.util.Arrays.asList;

List<Function<String, B>> transformers = asList(
        input -> "COMMON".equals(input) ? B.COMMON_VALUE : null,
        input -> "B".equals(input) ? B.B_VALUE : null);

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.convert;

Optional<B> result = convert("COMMON", transformers); // result.get() : B.COMMON_VALUE

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.convert;

Optional<B> result = convert("B", transformers); // result.get() : B.B_VALUE

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.convert;

Optional<B> result = convert("Other", transformers); // result : empty

The fluent way :

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.with;

Optional<B> result = with(transformers).convert("B"); // result.get() : B.B_VALUE

Default transformer

By default, the transformer will return the first target enum value name that is equal ignoring case to the input name/toString value.

See the next section about the default transformer Transformers.byEqualNamesIgnoringCase.

Prepared transformers

If you want to change the default transformation behavior, you have access at some already prepared for you in the EnumConverter.Transformers class:

• Transformers.byEqualNamesIgnoringCase(Class<T> targetClass) : The default transformer that returns the first target enum value name that is equal ignoring case to the input name/toString value.

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;

Optional<B> result = to(B.class).convert("COMMON_VALUE"); // result.get() : B.COMMON_VALUE

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;

Optional<B> result = to(B.class).convert("common_value"); // result.get() : B.COMMON_VALUE

• Transformers.byEqualNames(Class<T> targetClass) : A transformer that returns the first target enum value name that is equal to the input name/toString value.

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.convert;

Optional<B> result = convert("COMMON_VALUE", Transformers.byEqualNames(B.class)); // result.get() : B.COMMOM_VALUE

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.convert;

Optional<B> result = convert("common_value", Transformers.byEqualNames(B.class)); // result : empty

• Transformers.byExplicitMapping(Map<S, T> explicitMapping) : A transformer that uses a map to get corresponding target value for a given input.

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.with;

Map<A, B> mapping = new HashMap<>();
mapping.put(A.COMMON_VALUE, B.COMMON_VALUE);
mapping.put(A.A_VALUE, B.B_VALUE);

Optional<B> result = with(Transformers.byExplicitMapping(mapping)).convert(A.A_VALUE); // result.get() : B.B_VALUE

• Transformers.firstMatchingAgainstEnumValues(Class<T> targetClass, BiPredicate<String, String> matcher) : A transformer that test the input against each enum value's name until it matches.

// This does exactly the same transformation as the Transformers#byEqualNamesIgnoringCase
Transformers.firstMatchingAgainstEnumValues(
        B.class,
        (sourceName, targetName) -> targetName.equalsIgnoreCase(sourceName)
);

Converter as a Function

You can use the converter as a standard java.util.function.Function.

For Optional

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;
import static java.util.Optional.of;

Optional<B> result = of(A.COMMON_VALUE).map(to(B.class)); // result.get() : B.COMMON_VALUE

For Stream

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;
import static java.util.Arrays.asList;
import static java.util.stream.Collectors.toList;

List<B> result = asList(A.COMMON_VALUE, A.A_VALUE)
                .stream()
                .map(to(B.class))
                .collect(toList()); // result = [B.COMMON_VALUE, null]

Direct result

If you do not want an optional as a result, you can use the fonctional interface of the Function:

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;

B result = to(B.class).apply("COMMON_VALUE"); // result : B.COMMON_VALUE

import static com.ekino.oss.converter.jtrans4mers.EnumConverter.to;

B result = to(B.class).apply("A_VALUE"); // result : null