java如何仅对某些控制器使用Spring转换器？

Question

我有一个c转换器，它可以工作：

public class StringToLongConverter implements Converter<String, Long> {
    @Override
    public Long convert(String source) {
        Long myDecodedValue = ...
        return myDecodedValue;
    }
}

在web配置中，我有：

@Override
public void addFormatters (FormatterRegistry registry) {
    registry.addConverter(new StringToLongConverter());
}

一切都很好，但它适用于所有控制器，我需要它只执行一些控制器

//I need this controller to get myvalue from converter
@RequestMapping(value = "{myvalue}", method = RequestMethod.POST)
public ResponseEntity myvalue1(@PathVariable Long myvalue) {

    return new ResponseEntity<>(HttpStatus.OK);
}

//I need this controller to get myvalue without converter
@RequestMapping(value = "{myvalue}", method = RequestMethod.POST)
public ResponseEntity myvalue2(@PathVariable Long myvalue) {

    return new ResponseEntity<>(HttpStatus.OK);
}

我们是否可以指定哪些转换器或参数应与自定义转换器一起使用，哪些不应使用

Answer 1

通常来说，注册的Converter绑定到输入源和输出目标。在你的例子中<String, Long>。您使用的默认Spring转换器将在每个匹配的源-目标对上应用转换

为了更好地控制何时应用转换，可以使用^{}。该接口包含3种方法：

• boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType)，以确定是否应应用转换

• Set<ConvertiblePair> getConvertibleTypes()要返回一组源-目的地对，可将转换应用于

• Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType)实际转换发生的方法

我已经建立了一个小型Spring项目来使用ConditionalGenericConverter：

安魂曲版本。java:

// RequiresConversion is a custom annotation solely used in this example
// to annotate an attribute as "convertable"
@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
public @interface RequiresConversion {
}

SomeConverter。java:

@Component
public class SomeConverter implements ConditionalGenericConverter {

    @Override
    public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) {
        // Verify whether the annotation is present
        return targetType.getAnnotation(RequiresConversion.class) != null;
    }

    @Override
    public Set<ConvertiblePair> getConvertibleTypes() {
        return Collections.singleton(new ConvertiblePair(String.class, Long.class));
    }

    @Override
    public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) {
        // Conversion logic here
        // In this example it strips "value" from the source string
        String sourceValue = ((String) source).replace("value", "");
        return Long.valueOf(sourceValue);
    }
}

SomeController。java:

@RestController
public class SomeController {

    // The path variable used will be converted, resulting in the "value"-prefix 
    // being stripped in SomeConverter
    // Notice the custom '@RequiresConversion' annotation
    @GetMapping(value = "/test/{myvalue}")
    public ResponseEntity myvalue(@RequiresConversion @PathVariable Long myvalue) {
        return new ResponseEntity<>(HttpStatus.OK);
    }

    // As the @RequiresConversion annotation is not present,
    // the conversion is not applied to the @PathVariable
    @GetMapping(value = "/test2/{myvalue}")
    public ResponseEntity myvalue2(@PathVariable Long myvalue) {
        return new ResponseEntity<>(HttpStatus.OK);
    }
}

转换将在http://localhost:8080/test/value123上发生，从而产生一个123长的值。但是，由于第二个映射上不存在自定义注释@RequiresConversion，因此将跳过http://localhost:8080/test2/value123上的转换

您还可以通过将注释重命名为SkipConversion并验证该注释在matches()方法中是否不存在来反转注释

希望这有帮助