引言

当我们通过@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;/** * @author pader PropertyEditor 在不同的包下面 */@Slf4jpublic class CustomMovieEditor extends PropertyEditorSupportimplements PropertyEditorRegistrar { @Override public String getAsText() { Movie movie = (Movie) getValue(); return movie == null ? "" : movie.getName(); } @Override public void setAsText(String text) throws IllegalArgumentException { log.info("继承[PropertyEditorSupport]类,转换数据={}", text); String[] data = text.split("-"); Movie movie = Movie.builder().name(data[0] .toUpperCase()).seat(Integer.parseInt(data[1])) .build(); setValue(movie); } @Override public void registerCustomEditors(PropertyEditorRegistry registry) { registry.registerCustomEditor(Movie.class,this); }}

注册自定义的PropertyEditor

@Beanpublic CustomEditorConfigurer customEditorConfigurer() { CustomEditorConfigurer customEditorConfigurer = 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<?>,Class<? extends PropertyEditor>> maps = new HashMap<>(); maps.put(Movie.class,CustomMovieEditor.class); return customEditorConfigurer;}

Converter接口+@ConfigurationPropertiesBinding注解

//注意@Component@ConfigurationPropertiesBindingpublic class StringToPersonConverter implements Converter<String, Person> { @Override public Person convert(String from) { log.info("使用[Converter]接口,转换数据={}", from); String[] data = 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。
• @ConfigurationPropertiesBinding是限定符注解@Qualifier的派生类而已,参考org.springframework.boot.context.properties.ConversionServiceDeducer，以下是源代码片段

@Autowired(required = false)@ConfigurationPropertiesBindingpublic void setConverters(List<Converter<?, ?>> converters) { this.converters = converters;}/*** A list of custom converters (in addition to the defaults) to use when* converting properties for binding.* @param converters the converters to set*/@Autowired(required = false)@ConfigurationPropertiesBindingpublic void setGenericConverters(List<GenericConverter> converters) {this.genericConverters = 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，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：

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(); }}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。