[Java] Handling of JavaBeans in the method chain

I thought about how to handle objects created in JavaBeans in the method chain.

JavaBeans specification

I don't know if it's the exact specification, but the common JavaBeans specifications are as follows.

• Has a no-argument constructor
• Has properties (setter / getter)

There are many other things, but the important one is this one. Click here for official specifications → JavaBeans Spec

HogeBean.java

public class HogeBean {

    private String name;

    private String id;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getId() {
        return id;
    }

    public void setId(String id) {
        this.id = id;
    }
}

Like this. With lombok

HogeBean.java

@Data
public class HogeBean {

    private String name;

    private String id;
}

This is OK.

Problems with the method chain

For example, suppose you have a HogeBean and a FugaBean with similar fields.

HogeBean.java

@Data
public class HogeBean {

    private String name;

    private String id;
}

FugaBean.java

@Data
public class FugaBean {

    private String id;

    private String password;
}

If you want to convert HogeBean to FugaBean in Stream, think normally

List<HogeBean> hoges = ...

hoges.stream().map(hoge -> {

    FugaBean fuga = new FugaBean();
    fuga.setId(hoge.getId());
    return fuga;
    
}).Termination

I will write only like this. It's not so beautiful.

Solution 1 Anonymous class + instance initializer

It may not be very beautiful, but the curly braces + return in the map is a preventable pattern.

hoges.stream().map(hoge -> new FugaBean(){
    {
        setId(hoge.getId());
    }
}).Termination

It's much cleaner than before. But there are drawbacks

• Since it uses an anonymous class, it is not strictly that class. → There is a possibility of bugs such as reflection
• Cannot be used if the target class is final in the first place

Solution 2 Make the setter return itself so that you can create an object in one line.

The option to quit JavaBeans. Modify the setter as follows.

FugaBean.java

    public HogeBean setId(String id) {
        this.id = id;
        return this;
    }

For lombok, just add Accessors (chain = true)

FugaBean.java

@Data
@Accessors(chain = true)

The processing of the case can be done as follows

hoges.stream().map(hoge -> new FugaBean().setId(hoge.getId())).Termination

Refreshing. But after all there are drawbacks,

• Because it deviates from the JavaBeans specification, various things cannot be used (PropertyDescriptor, BeanUtils of apache, various frameworks)

Solution 3 Make a little builder

Like this

BeanCreater.java

public final class BeanCreater<T> {

    private BeanCreater() {
    }

    private T bean;

    public static <T> BeanCreater<T> of(Supplier<T> supplier) {

        BeanCreater<T> builder = new BeanCreater<T>();
        builder.bean = supplier.get();

        return builder;

    }
    
    public BeanCreater<T> construct(Consumer<T> consumer) {

        consumer.accept(this.bean);
        return this;
    }
    
    public T build() {
        return this.bean;
    }

}

With this,

hoges.stream().map(hoge -> BeanCreater.of(FugaBean::new)
    .construct(bean -> bean.setId(hoge.getId())).build()).Termination

Hmm. I tried it, but it's not good enough. The code is too noisy.

Conclusion

Personally, I like Solution 2 the most. It has a flowing interface, and there is no waste in essence and ritual talk. I hope JavaBeans will be more flexible considering the current situation. (I don't think that's the case ...) Click here for the BeanCreater created this time https://github.com/7tsuno/BeanCreater

Please advise if you have any other ideas!