SpringMVC自定义 Resolver疑问

可以的哦，试试看：

先定义一个自己的@UpperCase:

import java.lang.annotation.*;

@Documented
@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.METHOD, ElementType.FIELD, ElementType.PARAMETER, ElementType.ANNOTATION_TYPE})
public @interface UpperCase {

}

在定义一个formatter的工厂

import org.springframework.format.AnnotationFormatterFactory;
import org.springframework.format.Formatter;
import org.springframework.format.Parser;
import org.springframework.format.Printer;

import java.text.ParseException;
import java.util.Collections;
import java.util.HashSet;
import java.util.Locale;
import java.util.Set;

public class UpperAnnotationFormatterFactory implements AnnotationFormatterFactory<UpperCase> {

    @Override
    public Set<Class<?>> getFieldTypes() {
        Set<Class<?>> fieldTypes = new HashSet<>();
        fieldTypes.add(String.class);
        return Collections.unmodifiableSet(fieldTypes);
    }

    @Override
    public Printer<String> getPrinter(UpperCase annotation, Class<?> fieldType) {
        return configureFormatterFrom(annotation);
    }

    @Override
    public Parser<String> getParser(UpperCase annotation, Class<?> fieldType) {
        return configureFormatterFrom(annotation);
    }

    private Formatter<String> configureFormatterFrom(UpperCase annotation) {
       
        return new Formatter<String>() {
            @Override
            public String print(String object, Locale locale) {
                return object;
            }

            @Override
            public String parse(String text, Locale locale) throws ParseException {
                return text.toUpperCase();
            }
        };
    }
}

最后，注册一下上面这个工厂

import org.springframework.context.annotation.Configuration;
import org.springframework.format.FormatterRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

@Configuration
public class WebConfigurer implements WebMvcConfigurer {
    @Override
    public void addFormatters(FormatterRegistry registry) {
        registry.addFormatterForFieldAnnotation(new UpperAnnotationFormatterFactory());
    }
}

现在你再看看，你的代码

@RequestMapping(method = RequestMethod.GET)
   public String test(@RequestParam("title") @UpperCase String text) {
   System.out.println(text); // 这个地方的text就已经被大写了
   return "form";
}