Java 在 Spring Boot 中以编程方式注册 Spring Converter

Register Spring Converter Programmatically in Spring Boot

提问by jpolete

I want to register a Spring Converter in a Spring Boot project programmatically. In past Spring projects I've done it in XML like this...

我想以编程方式在 Spring Boot 项目中注册一个 Spring Converter。在过去的 Spring 项目中，我像这样用 XML 完成了...

<!-- Custom converters to allow automatic binding from Http requests parameters to objects -->
<!-- All converters are annotated w/@Component -->
<bean id="conversionService"
      class="org.springframework.context.support.ConversionServiceFactoryBean">
    <property name="converters">
        <list>
            <ref bean="stringToAssessmentConverter" />
        </list>
    </property>
</bean>

I'm trying to figure out how to do in Spring Boot's SpringBootServletInitializer

我试图弄清楚如何在 Spring Boot 的 SpringBootServletInitializer 中做

Update:I've made a little progress by passing the StringToAssessmentConverter as an argument to getConversionService, but now I'm getting a "No default constructor found"error for the StringToAssessmentConverter class. I'm not sure why Spring is not seeing the @Autowired constructor.

更新：通过将 StringToAssessmentConverter 作为参数传递给getConversionService，我取得了一些进展，但现在我收到了"No default constructor found"StringToAssessmentConverter 类的错误。我不确定为什么 Spring 没有看到 @Autowired 构造函数。

@SpringBootApplication
public class Application extends SpringBootServletInitializer {

    ...

    @Bean(name="conversionService")
    public ConversionServiceFactoryBean getConversionService(StringToAssessmentConverter stringToAssessmentConverter) {
        ConversionServiceFactoryBean bean = new ConversionServiceFactoryBean();

        Set<Converter> converters = new HashSet<>();

        converters.add(stringToAssessmentConverter);

        bean.setConverters(converters);
        return bean;
    }
}  

Here's the code for the Converter...

这是转换器的代码...

 @Component
 public class StringToAssessmentConverter implements Converter<String, Assessment> {

     private AssessmentService assessmentService;

     @Autowired
     public StringToAssessmentConverter(AssessmentService assessmentService) {
         this.assessmentService = assessmentService;
     }

     public Assessment convert(String source) {
         Long id = Long.valueOf(source);
         try {
             return assessmentService.find(id);
         } catch (SecurityException ex) {
             return null;
         }
     }
 }

Full Error

完全错误

Failed to execute goal org.springframework.boot:spring-boot-maven-
plugin:1.3.2.RELEASE:run (default-cli) on project yrdstick: An exception 
occurred while running. null: InvocationTargetException: Error creating 
bean with name
'org.springframework.boot.context.properties.ConfigurationPropertiesBindingPo
stProcessor': Invocation of init method failed; nested exception is 
org.springframework.beans.factory.UnsatisfiedDependencyException: Error 
creating bean with name 'conversionService' defined in 
me.jpolete.yrdstick.Application: Unsatisfied dependency expressed through 
constructor argument with index 0 of type 
[me.jpolete.yrdstick.websupport.StringToAssessmentConverter]: : Error 
creating bean with name 'stringToAssessmentConverter' defined in file 
[/yrdstick/target/classes/me/jpolete/yrdstick/websupport
/StringToAssessmentConverter.class]: Instantiation of bean failed; nested 
exception is org.springframework.beans.BeanInstantiationException: Failed 
to instantiate 
[me.jpolete.yrdstick.websupport.StringToAssessmentConverter]: No default 
constructor found; nested exception is java.lang.NoSuchMethodException: 
me.jpolete.yrdstick.websupport.StringToAssessmentConverter.<init>(); 
nested exception is 
org.springframework.beans.factory.BeanCreationException: Error creating 
bean with name 'stringToAssessmentConverter' defined in file [/yrdstick
/dev/yrdstick/target/classes/me/jpolete/yrdstick/websupport
/StringToAssessmentConverter.class]: Instantiation of bean failed; nested 
exception is org.springframework.beans.BeanInstantiationException: Failed 
to instantiate 
[me.jpolete.yrdstick.websupport.StringToAssessmentConverter]: No default 
constructor found; nested exception is java.lang.NoSuchMethodException: 
me.jpolete.yrdstick.websupport.StringToAssessmentConverter.<init>()

采纳答案by deFreitas

The answer is, you only need to anotate your converter as @Component:

答案是，您只需要将转换器注释为@Component：

This is my converter example

这是我的转换器示例

import org.springframework.core.convert.converter.Converter;
@Component
public class DateUtilToDateSQLConverter implements Converter<java.util.Date, Date> {

    @Override
    public Date convert(java.util.Date source) {
        return new Date(source.getTime());
    }
}

Then when Spring needs to make convert, the converter is called.

然后当 Spring 需要进行转换时，就会调用转换器。

My Spring Boot Version: 1.4.1

我的 Spring Boot 版本： 1.4.1

回答by MangEngkus

try this:

尝试这个：

@SpringBootApplication
public class Application extends SpringBootServletInitializer {

    @Bean
    public AssessmentService assessmentService(){
        return new AssessmentService();
    }

    @Bean
    public StringToAssessmentConverter stringToAssessmentConverter(){
        return new StringToAssessmentConverter(assessmentService());
    }

    @Bean(name="conversionService")
    public ConversionService getConversionService() {
        ConversionServiceFactoryBean bean = new ConversionServiceFactoryBean();    
        Set<Converter> converters = new HashSet<Converter>();

        //add the converter
        converters.add(stringToAssessmentConverter()); 

        bean.setConverters(converters);
        return bean.getObject();
    }

    // separate these class into its own java file if necessary
    // Assesment service
    class AssessmentService {}

    //converter
    class StringToAssessmentConverter implements Converter<String, Assessment> {

         private AssessmentService assessmentService;

         @Autowired
         public StringToAssessmentConverter(AssessmentService assessmentService) {
             this.assessmentService = assessmentService;
         }

         public Assessment convert(String source) {
             Long id = Long.valueOf(source);
             try {
                 return assessmentService.find(id);
             } catch (SecurityException ex) {
                 return null;
             }
         }

     }
}

or if your StringToAssessmentConverter is already a spring bean:

或者如果您的 StringToAssessmentConverter 已经是一个 spring bean：

@Autowired
@Bean(name="conversionService")
public ConversionService getConversionService(StringToAssessmentConverter stringToAssessmentConverter) {
    ConversionServiceFactoryBean bean = new ConversionServiceFactoryBean();    
    Set<Converter> converters = new HashSet<Converter>();

    //add the converter
    converters.add(stringToAssessmentConverter); 

    bean.setConverters(converters);
    return bean.getObject();
}

回答by narduk

Here is my solution:

这是我的解决方案：

A TypeConverter Annotation:

TypeConverter 注解：

@Target({ElementType.TYPE, ElementType.FIELD, ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Component
public @interface TypeConverter {
}

A Converter Registrar:

转换器注册商：

@Configuration
public class ConverterConfiguration {

    @Autowired(required = false)
    @TypeConverter
    private Set<Converter<?, ?>> autoRegisteredConverters;

    @Autowired(required = false)
    @TypeConverter
    private Set<ConverterFactory<?, ?>> autoRegisteredConverterFactories;

    @Autowired
    private ConverterRegistry converterRegistry;

    @PostConstruct
    public void conversionService() {
        if (autoRegisteredConverters != null) {
            for (Converter<?, ?> converter : autoRegisteredConverters) {
                converterRegistry.addConverter(converter);
            }
        }
        if (autoRegisteredConverterFactories != null) {
            for (ConverterFactory<?, ?> converterFactory : autoRegisteredConverterFactories) {
                converterRegistry.addConverterFactory(converterFactory);
            }
        }
    }

}

And then annotate your converters:

然后注释您的转换器：

@SuppressWarnings("rawtypes")
@TypeConverter
public class StringToEnumConverterFactory implements ConverterFactory<String, Enum> {

    @SuppressWarnings("unchecked")
    public <T extends Enum> Converter<String, T> getConverter(Class<T> targetType) {
        return new StringToEnum(targetType);
    }

    private final class StringToEnum<T extends Enum> implements Converter<String, T> {

        private Class<T> enumType;

        public StringToEnum(Class<T> enumType) {
            this.enumType = enumType;
        }

        @SuppressWarnings("unchecked")
        public T convert(String source) {
            return (T) Enum.valueOf(this.enumType, source.trim().toUpperCase());
        }
    }
}

回答by Grigory Kislin

For Spring Boot it looks like:

对于 Spring Boot，它看起来像：

public class MvcConfiguration implements WebMvcConfigurer {

  @Override
  public void addFormatters(FormatterRegistry registry) {
    // do not replace with lambda as spring cannot determine source type <S> and target type <T>
    registry.addConverter(new Converter<String, Integer>() {
        @Override
        public Integer convert(String text) {
            if (text == null) {
                return null;
            }
            String trimmed = StringUtils.trimWhitespace(text);
            return trimmed.equals("null") ? null : Integer.valueOf(trimmed);
        }
    });
  }

回答by fg78nc

If you are not on Spring Boot, where automatic registration of converters annotated with @Component (and similar stereotype annotations) is performed and you are **not in Web Mvc environment:

如果您不在 Spring Boot 上，在其中执行用 @Component（和类似的构造型注释）注释的转换器的自动注册，并且您 **不在 Web Mvc 环境中：

@Bean
ConversionService conversionService(ConversionServiceFactoryBean factory){
    ConversionServiceFactoryBean factory = new ConversionServiceFactoryBean();
    Set<Converter<?, ?>> convSet = new HashSet<Converter<?, ?>>();
    convSet.add(new MyConverter()); // or reference bean convSet.add(myConverter());
    factory.setConverters(convSet);
    factory.afterPropertiesSet();
    return factory.getObject();
}

回答by Anton

Also had problem with registration custom converter in xml config. Should to add converter id to annotation-driver

在 xml 配置中注册自定义转换器也有问题。应该将转换器 id 添加到 annotation-driver

<bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
        <property name="converters">
            <set>
                <bean class="ru.javawebinar.topjava.util.StringToLocalDateConverter"/>
            </set>
        </property>
</bean>

<mvc:annotation-driven conversion-service="conversionService"/>

Reference links: Spring MVC. Type Conversion,Spring Core. Type Conversion

参考链接： Spring MVC。类型转换，Spring 核心。类型转换