本篇内容主要讲解“Value注解支持对象类型ConfigurationProperties功能问题怎么解决”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“Value注解支持对象类型ConfigurationProperties功能问题怎么解决”吧!
真实业务场景
（不希望配置类注册为Bean 或 不希望声明@ConfigurationProperties）
假设某一个jar包内封装了DataSourceProperties
@Configuration@ConfigurationProperties( prefix = "my.datasource")@Datapublic class DataSourceProperties { private List<String> suffix; private List<DataSourceDetailProperties> db;}在jar包的Configuration中，某个@Bean的构造过程中引用了这个DataSourceProperties
public JdbcTemplate buildJdbcTemplate(DataSourceProperties dataSourceProperties) {}在某个业务场景中，同时存在两个DataSourceProperties 会造成一个问题，注入的时候会提示有多个候选的bean 但是没法去修改Jar包中的内容
自己重复写一个DataSourceProperties 不是很优雅
这时候引出了一个需求，DataSourceProperties不希望注册为Bean，但是能够从配置文件读取构建对象
解决方案一
使用org.springframework.boot.context.properties.bind.Binder 从配置文件构建配置对象
@Beanpublic JdbcTemplate buildJdbcTemplate(Environment environment) { Binder binder = Binder.get(environment); DataSourceProperties properties1 = binder.bind("my.datasource1", Bindable.of(DataSourceProperties.class)).get(), properties2 = binder.bind("my.datasource2", Bindable.of(DataSourceProperties.class)).get();}binder.bind("xxx", Bindable.of(type)).get() 似乎是重复的编码方式？
解决方案二
使@Value注解能够支持自动调用这段代码 binder.bind("xxx", Bindable.of(type)).get() 例如
@Beanpublic JdbcTemplate buildJdbcTemplate(@Value("my.datasource1") DataSourceProperties properties1, @Value("my.datasource2") DataSourceProperties properties2) { }org.springframework.beans.factory.support.DefaultListableBeanFactory#doResolveDependency 最后会交由converter处理
Class<?> type = descriptor.getDependencyType();Object value = getAutowireCandidateResolver().getSuggestedValue(descriptor);if (value != null) { if (value instanceof String) { String strVal = resolveEmbeddedValue((String) value); BeanDefinition bd = (beanName != null && containsBean(beanName) ? getMergedBeanDefinition(beanName) : null); value = evaluateBeanDefinitionString(strVal, bd); } TypeConverter converter = (typeConverter != null ? typeConverter : getTypeConverter()); try { return converter.convertIfNecessary(value, type, descriptor.getTypeDescriptor()); } catch (UnsupportedOperationException ex) { // A custom TypeConverter which does not support TypeDescriptor resolution... return (descriptor.getField() != null ? converter.convertIfNecessary(value, type, descriptor.getField()) : converter.convertIfNecessary(value, type, descriptor.getMethodParameter())); }}项目启动时，添加String to Object的转换器，支持@Value 并且 "bind:"开头（防止影响@Value原有功能）
package com.nuonuo.accounting.guiding.support.spring;import org.springframework.beans.factory.annotation.Value;import org.springframework.boot.context.properties.bind.Bindable;import org.springframework.boot.context.properties.bind.Binder;import org.springframework.boot.convert.ApplicationConversionService;import org.springframework.context.ApplicationContextInitializer;import org.springframework.context.ConfigurableApplicationContext;import org.springframework.core.convert.TypeDescriptor;import org.springframework.core.convert.converter.ConditionalGenericConverter;import java.util.Set;import static java.util.Collections.singleton;public class ValuePropertiesBindableAnnotationSupport implements ApplicationContextInitializer<ConfigurableApplicationContext> { private static final String PREFIX = "bind:"; @Override public void initialize(ConfigurableApplicationContext context) { Binder binder = Binder.get(context.getEnvironment()); ((ApplicationConversionService) context.getBeanFactory().getConversionService()).addConverter(new ConditionalGenericConverter() { @Override public boolean matches(TypeDescriptor sourceType, TypeDescriptor targetType) { Value value = targetType.getAnnotation(Value.class); return value != null && value.value().startsWith(PREFIX); } @Override public Set<ConvertiblePair> getConvertibleTypes() { return singleton(new ConvertiblePair(String.class, Object.class)); } @Override public Object convert(Object source, TypeDescriptor sourceType, TypeDescriptor targetType) { Value value = targetType.getAnnotation(Value.class); Class<?> type = targetType.getType(); assert value != null; return binder.bind(value.value().replace(PREFIX, ""), Bindable.of(type)).get(); } }); }}转换后代码执行 binder.bind(value.value().replace(PREFIX, ""), Bindable.of(type)).get(); 目的就达成了
在META-INF/spring.factories中添加注册的Bean
# ApplicationContextInitializerorg.springframework.context.ApplicationContextInitializer=\com.nuonuo.accounting.guiding.support.spring.ValuePropertiesBindableAnnotationSupport,\最终效果
@Beanpublic JdbcTemplate buildJdbcTemplate(@Value("bind:my.datasource1") DataSourceProperties properties1, @Value("bind:my.datasource2") DataSourceProperties properties2) { }到此，相信大家对“Value注解支持对象类型ConfigurationProperties功能问题怎么解决”有了更深的了解，不妨来实际操作一番吧！这里是编程网网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！
