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# Spring的Convert

![](https://1360295607-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LATEhlAPqBUOhHPcpUO%2F-LQihxhFePwIvLulZTM1%2F-LQiiJzIyN803wyYwMUv%2F%E5%B1%8F%E5%B9%95%E5%BF%AB%E7%85%A7%202018-11-07%20%E4%B8%8B%E5%8D%8810.52.29.png?generation=1541603415208331\&alt=media)

Converter则是Spring中的类型转换器，将S类型的source对象转换为T类型的对象

```java
public interface Converter<S, T> {

    T convert(S source);
}
```

为了将不同类型转换器集中起来，Spring定义了ConverterRegistry来添加或移除转换器：

```java
�public interface ConverterRegistry {

    void addConverter(Converter<?, ?> converter);

    <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);
}
```

Spring将类型转换抽象为一种服务，叫做ConversionService，既然叫类型转换服务，则需要提供类型转换的方法：

```java
public interface ConversionService {
    //sourceType是否可以转换为targetType
    boolean canConvert(@Nullable Class<?> sourceType, Class<?> targetType);

    //sourceType是否可以转换为targetType
    boolean canConvert(@Nullable TypeDescriptor sourceType, TypeDescriptor targetType);

    //将source对象转换为targetType类型的对象
    <T> T convert(@Nullable Object source, Class<T> targetType);

    //将sourceType类型的source对象转换为targetType类型的对象
    Object convert(@Nullable Object source, @Nullable TypeDescriptor sourceType, TypeDescriptor targetType);
}
```

ConfigurableConversionService意为可配置的转换服务，既然可配置，则表示可以任意增减转换器：

```java
public interface ConfigurableConversionService extends ConversionService, ConverterRegistry {

}
```

GenericConversionService是ConfigurableConversionService的基本实现，

�DefaultConversionService则在GenericConversionService的基础上，内部添加了常用的类型转换器。�

**�TODO Spring的Formatter接口�**

## 参考

[Spring源码：Converter及TypeConverter类解析](/way-to-architect/kuang-jia-huo-gong-ju/spring/springji-chu/springshi-xian-zhong-de-zhu-yao-lei/s-pringzhong-de-conversionservice.md)