Spring源码：ConversionService类解析

2019年3月18日 384次阅读 来源: Spring Boot

整体类图：一般来说，用户可以使⽤用内置的或者⾃己实现Converter接⼝来实现类型转换，ConversionService类接口内部调用Converter接口实现类来实现类型转换

《Spring源码：ConversionService类解析》

  • ConversionService接口：类型转换的服务接口，这是转换系统的入口，调用convert(Object, Class)进行一次线程安全的类型转换。

    public interface ConversionService {

boolean canConvert(Class<?> sourceType, Class<?> targetType);

boolean canConvert(TypeDescriptor sourceType, TypeDescriptor targetType);

  // 转换过程：首先获取合适的转换器（DefaultConversionService会配置默认的转换器，也可自定义），然后进行转换
<T> T convert(Object source, Class<T> targetType);

Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType);
}

  • ConverterRegistry接口：对转换器进行注册，对于ConversionService和ConverterRegistry的主要实现类是GenericConversionService。

    public interface ConverterRegistry {

<S, T> void addConverter(Class<S> sourceType, Class<T> targetType, Converter<? super S, ? extends T> converter);

void addConverter(GenericConverter converter);

void addConverterFactory(ConverterFactory<?, ?> factory);

void removeConvertible(Class<?> sourceType, Class<?> targetType);

}

  • **GenericConversionService类：**ConversionService和ConverterRegistry的主要实现类，GenericConversionService维护了一个内部类的对象Converters。

    public class GenericConversionService implements ConfigurableConversionService {

private final Converters converters = new Converters();

private final Map<ConverterCacheKey, GenericConverter> converterCache =
        new ConcurrentReferenceHashMap<ConverterCacheKey, GenericConverter>(64);

  // ......
}

public interface ConfigurableConversionService extends ConversionService, ConverterRegistry {

}

  • DefaultConversionService类：默认转换器配置的GenericConversionService继承类，适用于大多数环境的转换器。spring的注册类型转换器时，是通过GenericConversionService的子类DefaultConversionService实现的

    public class DefaultConversionService extends GenericConversionService {
// ......
}

  • ConversionServiceFactoryBean类：一个工厂类，可以方便地访问配置了适用于大多数环境的转换器的ConversionService。

    public class ConversionServiceFactoryBean implements FactoryBean<ConversionService>, InitializingBean {

private Set<?> converters;
private GenericConversionService conversionService;


public void setConverters(Set<?> converters) {
    this.converters = converters;
}

@Override
public void afterPropertiesSet() {
    this.conversionService = createConversionService();
    ConversionServiceFactory.registerConverters(this.converters, this.conversionService);
}

protected GenericConversionService createConversionService() {
    return new DefaultConversionService();
}

@Override
public ConversionService getObject() {
    return this.conversionService;
}

@Override
public Class<? extends ConversionService> getObjectType() {
    return GenericConversionService.class;
}

@Override
public boolean isSingleton() {
    return true;
}
}

    用法，如：

    <bean id="conversionService" class="org.springframework.context.support.ConversionServiceFactoryBean">
  <property name="converters">
      <list>
          <bean class="example.MyCustomConverter"/>
      </list>
  </property>
</bean>
    原文作者：Spring Boot
    原文地址: https://blog.csdn.net/zhuqiuhui/article/details/82316720
    本文转自网络文章，转载此文章仅为分享知识，如有侵权，请联系博主进行删除。
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