Condition实现类中注入bean

Question

烦请各位帮忙看看如何解决

背景描述

最近写了个springboot的后台，通过yaml配置了一些环境信息，写入到一个自建的实体。初衷是想通过一键式配置实现生产环境和测试环境中对RabbitMQ监听的切换，但是在bean的注入过程中出现了问题。
原思路：自定义condition接口的实现类，在实现类中注入yaml关联的配置类，根据配置信息确定实现类返回的boolean，最后利用@Conditional注解中的参数（即上文描述的boolean）控制RabbitMQ的监听类是否生效。

问题相关代码

版本实体类

/**
 * 版本实体
 */
@Data
@Component
@ConfigurationProperties(prefix="ecc-plus")
public class ECP_PLUS {
    private String version;//版本号
    private String pubtime;//发布时间
    private String publisher;//发布人
    private String comments;//发布说明
    private String rsHadNotReadPre;//redis 消息未读键前缀
    private Boolean pubVersion;//是否是正式版本
    private String msgDbName;//消息数据库名称
}

自定义配置

#yaml配置
ecc-plus:
  version: 1.2.0.RELEASE
  pubtime: 2022-07-07
  publisher: wayne
  comments: 修复了一些已知的bug。
  rs-had-not-read-pre: usr-hadRead-  #消息未读键前缀
  pub-version: true #是否是发布版本
  msg-db-name: terminal2022

自定义Condition实现类

/**
 * 生产环境
 * 控制动态加载监听Mq监听Bean的注入
 */
@Component
public class MsgMqProdCondition implements Condition {
    @Autowired
    private ECP_PLUS ecp_plus;

    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        boolean flag = false;
        //flag = ecp_plus.getPubVersion()==true? true:false;
        return flag;
    }
}

MQ监听

/**
 * RabbitMQ监听-开发
 */
@Component
@Lazy(false)
@Conditional(MsgMqProdCondition.class)
public class RabbitMqListener {
      /**
     * 监听异步处理消息标签请求
     * @param msg
     * @param channel
     */
    @RabbitListener(queues = MsgRabbitMqConfig.TAG_QUEUE_NAME)//正式环境
    public void listenTagMQ_PROD(Message msg,Channel channel){
        String jsonStr = new String(msg.getBody());
        JSONObject msgJson = JSON.parseObject(jsonStr);
        String code = msgJson.getString("CODE");
        MSG_TAG_SCAT tag =msgJson.getObject("tags",MSG_TAG_SCAT.class);
        if (tag!=null){
            msgService.asynDueMsgTag(code,tag);
        }
    }
}

运行结果及报错内容

在启动过程中，condition实现类自动注入的实体类是null

按照我之前的写法这里就会报空指针，目测问题应该是出在bean的生命周期上，想请教各位，这种场景应该如何让配置实体先加载呢？

Answer 1

原因分析

原因在于我的思路过于僵化了，原本的思路一心只想自己将装配好的ECP_PLUS注入到Condition中，而忽略了Condition接口中关键方法matches的参数ConditionContext，其实通过它就可以直接拿yml的值，下面是源码（可自行跳过）。

关键源码

ConditionContext部分源码

/**
 * Context information for use by {@link Condition} implementations.
 *
 * @author Phillip Webb
 * @author Juergen Hoeller
 * @since 4.0
 */
public interface ConditionContext {

    /**
     * Return the {@link BeanDefinitionRegistry} that will hold the bean definition
     * should the condition match.
     * @throws IllegalStateException if no registry is available (which is unusual:
     * only the case with a plain {@link ClassPathScanningCandidateComponentProvider})
     */
    BeanDefinitionRegistry getRegistry();

    /**
     * Return the {@link ConfigurableListableBeanFactory} that will hold the bean
     * definition should the condition match, or {@code null} if the bean factory is
     * not available (or not downcastable to {@code ConfigurableListableBeanFactory}).
     */
    @Nullable
    ConfigurableListableBeanFactory getBeanFactory();

    /**
     * Return the {@link Environment} for which the current application is running.
     */
    Environment getEnvironment();

    /**
     * Return the {@link ResourceLoader} currently being used.
     */
    ResourceLoader getResourceLoader();

    /**
     * Return the {@link ClassLoader} that should be used to load additional classes
     * (only {@code null} if even the system ClassLoader isn't accessible).
     * @see org.springframework.util.ClassUtils#forName(String, ClassLoader)
     */
    @Nullable
    ClassLoader getClassLoader();

}

ConditionContext接口中的getEnvironment()方法引起了我的注意，我们继续看这个方法的返回值；

/**
 * Interface representing the environment in which the current application is running.
 * Models two key aspects of the application environment: <em>profiles</em> and
 * <em>properties</em>. Methods related to property access are exposed via the
 * {@link PropertyResolver} superinterface.
 *
 * <p>A <em>profile</em> is a named, logical group of bean definitions to be registered
 * with the container only if the given profile is <em>active</em>. Beans may be assigned
 * to a profile whether defined in XML or via annotations; see the spring-beans 3.1 schema
 * or the {@link org.springframework.context.annotation.Profile @Profile} annotation for
 * syntax details. The role of the {@code Environment} object with relation to profiles is
 * in determining which profiles (if any) are currently {@linkplain #getActiveProfiles
 * active}, and which profiles (if any) should be {@linkplain #getDefaultProfiles active
 * by default}.
 *
 * <p><em>Properties</em> play an important role in almost all applications, and may
 * originate from a variety of sources: properties files, JVM system properties, system
 * environment variables, JNDI, servlet context parameters, ad-hoc Properties objects,
 * Maps, and so on. The role of the {@code Environment} object with relation to properties
 * is to provide the user with a convenient service interface for configuring property
 * sources and resolving properties from them.
 *
 * <p>Beans managed within an {@code ApplicationContext} may register to be {@link
 * org.springframework.context.EnvironmentAware EnvironmentAware} or {@code @Inject} the
 * {@code Environment} in order to query profile state or resolve properties directly.
 *
 * <p>In most cases, however, application-level beans should not need to interact with the
 * {@code Environment} directly but instead may have to have {@code ${...}} property
 * values replaced by a property placeholder configurer such as
 * {@link org.springframework.context.support.PropertySourcesPlaceholderConfigurer
 * PropertySourcesPlaceholderConfigurer}, which itself is {@code EnvironmentAware} and
 * as of Spring 3.1 is registered by default when using
 * {@code <context:property-placeholder/>}.
 *
 * <p>Configuration of the {@code Environment} object must be done through the
 * {@code ConfigurableEnvironment} interface, returned from all
 * {@code AbstractApplicationContext} subclass {@code getEnvironment()} methods. See
 * {@link ConfigurableEnvironment} Javadoc for usage examples demonstrating manipulation
 * of property sources prior to application context {@code refresh()}.
 *
 * @author Chris Beams
 * @since 3.1
 * @see PropertyResolver
 * @see EnvironmentCapable
 * @see ConfigurableEnvironment
 * @see AbstractEnvironment
 * @see StandardEnvironment
 * @see org.springframework.context.EnvironmentAware
 * @see org.springframework.context.ConfigurableApplicationContext#getEnvironment
 * @see org.springframework.context.ConfigurableApplicationContext#setEnvironment
 * @see org.springframework.context.support.AbstractApplicationContext#createEnvironment
 */
public interface Environment extends PropertyResolver {

    /**
     * Return the set of profiles explicitly made active for this environment. Profiles
     * are used for creating logical groupings of bean definitions to be registered
     * conditionally, for example based on deployment environment. Profiles can be
     * activated by setting {@linkplain AbstractEnvironment#ACTIVE_PROFILES_PROPERTY_NAME
     * "spring.profiles.active"} as a system property or by calling
     * {@link ConfigurableEnvironment#setActiveProfiles(String...)}.
     * <p>If no profiles have explicitly been specified as active, then any
     * {@linkplain #getDefaultProfiles() default profiles} will automatically be activated.
     * @see #getDefaultProfiles
     * @see ConfigurableEnvironment#setActiveProfiles
     * @see AbstractEnvironment#ACTIVE_PROFILES_PROPERTY_NAME
     */
    String[] getActiveProfiles();

    /**
     * Return the set of profiles to be active by default when no active profiles have
     * been set explicitly.
     * @see #getActiveProfiles
     * @see ConfigurableEnvironment#setDefaultProfiles
     * @see AbstractEnvironment#DEFAULT_PROFILES_PROPERTY_NAME
     */
    String[] getDefaultProfiles();

    /**
     * Return whether one or more of the given profiles is active or, in the case of no
     * explicit active profiles, whether one or more of the given profiles is included in
     * the set of default profiles. If a profile begins with '!' the logic is inverted,
     * i.e. the method will return {@code true} if the given profile is <em>not</em> active.
     * For example, {@code env.acceptsProfiles("p1", "!p2")} will return {@code true} if
     * profile 'p1' is active or 'p2' is not active.
     * @throws IllegalArgumentException if called with zero arguments
     * or if any profile is {@code null}, empty, or whitespace only
     * @see #getActiveProfiles
     * @see #getDefaultProfiles
     * @see #acceptsProfiles(Profiles)
     * @deprecated as of 5.1 in favor of {@link #acceptsProfiles(Profiles)}
     */
    @Deprecated
    boolean acceptsProfiles(String... profiles);

    /**
     * Return whether the {@linkplain #getActiveProfiles() active profiles}
     * match the given {@link Profiles} predicate.
     */
    boolean acceptsProfiles(Profiles profiles);

}

可以看到Environment这个接口描述了大量的关于环境配置的信息，这里我们梳理一下这些接口的实现关系。

底层接口PropertyResolver源码

/*
 * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.env;

import org.springframework.lang.Nullable;

/**
 * Interface for resolving properties against any underlying source.
 *
 * @author Chris Beams
 * @author Juergen Hoeller
 * @since 3.1
 * @see Environment
 * @see PropertySourcesPropertyResolver
 */
public interface PropertyResolver {

    /**
     * Return whether the given property key is available for resolution,
     * i.e. if the value for the given key is not {@code null}.
     */
    boolean containsProperty(String key);

    /**
     * Return the property value associated with the given key,
     * or {@code null} if the key cannot be resolved.
     * @param key the property name to resolve
     * @see #getProperty(String, String)
     * @see #getProperty(String, Class)
     * @see #getRequiredProperty(String)
     */
    @Nullable
    String getProperty(String key);

    /**
     * Return the property value associated with the given key, or
     * {@code defaultValue} if the key cannot be resolved.
     * @param key the property name to resolve
     * @param defaultValue the default value to return if no value is found
     * @see #getRequiredProperty(String)
     * @see #getProperty(String, Class)
     */
    String getProperty(String key, String defaultValue);

    /**
     * Return the property value associated with the given key,
     * or {@code null} if the key cannot be resolved.
     * @param key the property name to resolve
     * @param targetType the expected type of the property value
     * @see #getRequiredProperty(String, Class)
     */
    @Nullable
    <T> T getProperty(String key, Class<T> targetType);

    /**
     * Return the property value associated with the given key,
     * or {@code defaultValue} if the key cannot be resolved.
     * @param key the property name to resolve
     * @param targetType the expected type of the property value
     * @param defaultValue the default value to return if no value is found
     * @see #getRequiredProperty(String, Class)
     */
    <T> T getProperty(String key, Class<T> targetType, T defaultValue);

    /**
     * Return the property value associated with the given key (never {@code null}).
     * @throws IllegalStateException if the key cannot be resolved
     * @see #getRequiredProperty(String, Class)
     */
    String getRequiredProperty(String key) throws IllegalStateException;

    /**
     * Return the property value associated with the given key, converted to the given
     * targetType (never {@code null}).
     * @throws IllegalStateException if the given key cannot be resolved
     */
    <T> T getRequiredProperty(String key, Class<T> targetType) throws IllegalStateException;

    /**
     * Resolve ${...} placeholders in the given text, replacing them with corresponding
     * property values as resolved by {@link #getProperty}. Unresolvable placeholders with
     * no default value are ignored and passed through unchanged.
     * @param text the String to resolve
     * @return the resolved String (never {@code null})
     * @throws IllegalArgumentException if given text is {@code null}
     * @see #resolveRequiredPlaceholders
     */
    String resolvePlaceholders(String text);

    /**
     * Resolve ${...} placeholders in the given text, replacing them with corresponding
     * property values as resolved by {@link #getProperty}. Unresolvable placeholders with
     * no default value will cause an IllegalArgumentException to be thrown.
     * @return the resolved String (never {@code null})
     * @throws IllegalArgumentException if given text is {@code null}
     * or if any placeholders are unresolvable
     */
    String resolveRequiredPlaceholders(String text) throws IllegalArgumentException;

}

破案的关键就是这个getProperty(String key)

通过ConditionContext直接获取yml中的配置

直接调用

public class MsgMqProdCondition implements Condition {
    @Override
    public boolean matches(ConditionContext context, AnnotatedTypeMetadata metadata) {
        boolean flag = false;
        String property = context.getEnvironment().getProperty("ecc-plus.pub-version");
        if (property.equals("true")){
            flag=true;
        }
        return flag;
    }
}

如有谬误，欢迎各位批评指正，感激不尽。