Support for builder pattern to construct objects of custom classes

[kravemir]

I would like to use TOML (toml4j) for (de)serialization of model classes for my project. I strongly prefer value based approach to model classes, and use immutable classes with builder pattern for construction.

I found support for custom classes in README.md, but there's no mention of builder pattern support, therefore I assume it's not implemented. However, I would be very glad to have such feature.

Also, as my project uses models defined in another project. I would like to use builder based construction without need of annotations (ie. annotation based configuration is optional).

For example:

TomlTypeRegistry registry = new TomlTypeRegistry();
registry.add(Address.class, "builder", "build");
registry.add(User.class, "newBuilder", "create");

User user = new Toml().read(tomlFile).to(User.class);

Assume for example:

class Address {
    // ....

    static class Builder {
        // ... setProperty(Type value) methods ...

        Address build();
    }

    static Builder builder();
}

class User {
    // ....

    static class Builder {
        // ... setProperty(Type value) methods ...

        User create();
    }

    static Builder newBuilder();
}

[mwanji]

Thanks for the interest! I'm not sure I understand what toml4j would pass to the builder, or why built-in support is needed. Is this builder auto-generated or hand-written?

[kravemir]

I'm not sure I understand what toml4j would pass to the builder

The same thing as to custom classes. When populating custom classes, (I think) the process is following:

• create new instance custom class (new CustomClass()),
• deserialize properties (recusive process, if property is also custom class),
• set properties using setter methods (instance.setName(value), instance.setOther(value), ... ),
• return populated instance of custom class.

When deserializing to custom classes instantiated via builder, process is following:

• create new instance of builder (CustomClass.newBuilder()),
• deserialize properties (recusive process, if property is also custom class),
• set properties using setter methods (builder.setName(value), builder.setOther(value), ... ),
• build instance using builder ( instance = builder.build() ),
• return built instance.

or why built-in support is needed

Not needed, and could be created on top of toml4j. But, it would be useful for projects using value-based approach to model classes.

Is this builder auto-generated or hand-written?

Usually auto-generated. Either by IDE's extensions, or via annotation processing (lombok, immutables, google-auto,...), or from contract definition (Google Protocol Buffers, ...).

[kravemir]

@mwanji actually, I'm much more concerned about legal stuff mentioned in #56, that this feature. Legal stuff is blocker,... Feature I can write on my own, and also contribute as PR to this project (if you would welcome it),... But, legal stuff has to be solved by library's author.