Does Java bean's setter permit return this?

Question

can I define setter method to return this rather than void?

Like:

ClassA setItem1() {
      return this;
}

ClassA setItem2() {
      return this;
}
         


        

Answer 1

I would guess this is not in violation of the JavaBean specification, although I am not sure of it.

Check out the following example:

public class JavaBean {

    private String value;

    public String getValue() {
        return value;
    }

    public JavaBean setValue(String value) {
        this.value = value;
        return this;
    }

    public static void main(String[] args) throws Exception {
        JavaBean bean = new JavaBean();
        JavaBean.class.getMethod("setValue", String.class).invoke(bean, "test");
        System.out.println(bean.getValue());
    }
}

Many frameworks access JavaBeans using the reflection API. As you can see above, accessing a settter which returns 'this' is not influenced by the return type (the return type is not used to locate a method via reflection). It also makes sense, because you cannot have two methods in one scope that are identical except for their return type.