SpringBoot2.0配置属性自定义转换

引言

当我们通过&＃64;ConfigurationProperties注解实现配置 bean的时候,如果默认的配置属性转换无法满足我们的需求的时候,我们可以根据自己的需求通过以下扩展方式对配置属性进行转换

PropertyEditorSupport实现

下面的例子是把属性中定义的字符串转换成Movie,并且把name的值大写

• 继承PropertyEditorSupport并且实现PropertyEditorRegistrar接口

package com.paderlol.spring.practice.properties.editor;import com.paderlol.spring.practice.properties.pojo.Movie;
import java.beans.PropertyEditorSupport;
import lombok.extern.slf4j.Slf4j;
import org.springframework.beans.PropertyEditorRegistrar;
import org.springframework.beans.PropertyEditorRegistry;/*** &＃64;author pader PropertyEditor 在不同的包下面*/
&＃64;Slf4j
public class CustomMovieEditor extends PropertyEditorSupport
implements PropertyEditorRegistrar {&＃64;Overridepublic String getAsText() {Movie movie &＃61; (Movie) getValue();return movie &＃61;&＃61; null ? "" : movie.getName();}&＃64;Overridepublic void setAsText(String text) throws IllegalArgumentException {log.info("继承[PropertyEditorSupport]类,转换数据&＃61;{}", text);String[] data &＃61; text.split("-");Movie movie &＃61; Movie.builder().name(data[0].toUpperCase()).seat(Integer.parseInt(data[1])).build();setValue(movie);}&＃64;Overridepublic void registerCustomEditors(PropertyEditorRegistry registry) {registry.registerCustomEditor(Movie.class,this);}
}

• 注册自定义的PropertyEditor

&＃64;Bean
public CustomEditorConfigurer customEditorConfigurer() {CustomEditorConfigurer customEditorConfigurer &＃61; new CustomEditorConfigurer(); // 有两种注册方式 这是第一种customEditorConfigurer.setPropertyEditorRegistrars( new PropertyEditorRegistrar[]{ new CustomMovieEditor() });// 第二 种Map,Class> maps &＃61; new HashMap<>();maps.put(Movie.class,CustomMovieEditor.class);return customEditorConfigurer;
}

Converter接口&＃43;&＃64;ConfigurationPropertiesBinding注解

//注意
&＃64;Component
&＃64;ConfigurationPropertiesBinding
public class StringToPersonConverter implements Converter {&＃64;Overridepublic Person convert(String from) {log.info("使用[Converter]接口,转换数据&＃61;{}", from);String[] data &＃61; from.split(",");return Person.builder().name(data[0]).age(Integer.parseInt(data[1])).build();}
}

总结

• 以上两种实现方式结果,但是Converter接口相比PropertyEditor接口更加灵活一些,PropertyEditor接口仅限于String转换,Converter可以自定义别的,并且PropertyEditor接口通常用于Controller中的接收参数的转换。
• &＃64;ConfigurationPropertiesBinding是限定符注解&＃64;Qualifier的派生类而已,参考org.springframework.boot.context.properties.ConversionServiceDeducer&＃xff0c;以下是源代码片段

&＃64;Autowired(required &＃61; false)
&＃64;ConfigurationPropertiesBinding
public void setConverters(List> converters) {this.converters &＃61; converters;
}/**
* A list of custom converters (in addition to the defaults) to use when
* converting properties for binding.
* &＃64;param converters the converters to set
*/
&＃64;Autowired(required &＃61; false)
&＃64;ConfigurationPropertiesBinding
public void setGenericConverters(List converters) {
this.genericConverters &＃61; converters;}

• Formatter接口是不能对属性完成转换的,因为ConversionServiceDeducer初始化的时候只获取GenericConverter和Converter接口
• 官方文档上还介绍了可以使用实现org.springframework.core.convert.ConversionService并且Bean名称也必须叫conversionService&＃xff0c;不过大部分情况不推荐自己通过这种方式去实现这个接口,因为自己实现的ConversionService会替代默认的。具体参考ConversionServiceDeducer源码&＃xff1a;

public ConversionService getConversionService() {try {//默认首先寻找Bean名称叫conversionService的ConversionService的Bean类return this.applicationContext.getBean(ConfigurableApplicationContext.CONVERSION_SERVICE_BEAN_NAME,ConversionService.class);}catch (NoSuchBeanDefinitionException ex) {//找不到就默认生成ApplicationConversionService类return this.applicationContext.getAutowireCapableBeanFactory().createBean(Factory.class).create();}
}