Convert anonymous inner class to Java 8 lambda

Question

Sonar static code analysis tells me this is a code smell and should be converted to a lamdba.

 public WebMvcConfigurer corsConfigurer() {
        return new WebMvcConfigurer() {
            @Override
            public void addCorsMappings(CorsRegistry registry) {
                registry.addMapping("/**")
               .allowedOrigins("*")
               .allowedMethods("*");
            }
        };
    }

I've tried various approaches with no luck. Any help is appreciated.

What have you tried and what is/are the problem(s) you have encountered? — rmlan
– rmlan, Commented Jun 6, 2018 at 23:53

Jacob G. · Accepted Answer · 2018-06-06 23:55:50Z

4

Assuming WebMvcConfigurer is a functional interface, the method can be changed to the following:

public WebMvcConfigurer corsConfigurer() {
     return registry -> registry.addMapping("/**")
                                .allowedOrigins("*")
                                .allowedMethods("*");
}

answered Jun 6, 2018 at 23:55

Jacob G.

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3 Comments

Justin James Over a year ago

Thanks Jacob. This produced: [ERROR] incompatible types: org.springframework.web.servlet.config.annotation.WebMvcConfigurer is not a functional interface no abstract method found in interface org.springframework.web.servlet.config.annotation.WebMvcConfigurer

Jacob G. Over a year ago

Yep, this only works if WebMvcConfigurer is a functional interface, which it apparently isn't. The only other option is to create your own functional interface that extends WebMvcConfigurer.

yshavit Over a year ago

This may be a bug in sonar. Looking at WebMvcConfigurer, all of its methods are default. It could be that sonar thinks it's a functional interface because it doesn't have more than one abstract method; it should instead be checking that it had exactly one.

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