背景

最近为了给kafka加性能指标采集功能，调研后发现spring-kafka在2.3版本之后就自带了Micrometer指标采集功能。但是当前项目的spring-boot版本是2.0.2.RELEASE，对应的spring-kafka版本是2.1.6.RELEASE，所以准备将spring-boot版本升级到2.7.18，这是2.x系列的最高版本，对应的spring-kafka版本是2.8.11。

版本升级

module升级前version升级后version
spring-boot2.0.2.RELEASE2.7.18
spring-webmvc5.0.6.RELEASE5.3.31
spring-kafka2.1.6.RELEASE2.8.11

不兼容的地方

Spring boot

2.6版本开始默认禁用Bean的循环依赖

项目启动会检测是否存在循环依赖，存在就报如下错误。

***************************
APPLICATION FAILED TO START
***************************

Description:

The dependencies of some of the beans in the application context form a cycle:

   collectionController (field private com.biz.manager.CollectionManager com.web.controller.CollectionController.collectionManager)
┌─────┐
|  collectionManagerImpl (field private com.biz.manager.FunnyManager com.biz.manager.impl.CollectionManagerImpl.funnyManager)
↑     ↓
|  funnyManagerImpl (field private com.biz.manager.CollectionManager com.biz.manager.impl.FunnyManagerImpl.collectionManager)
└─────┘

Action:

Relying upon circular references is discouraged and they are prohibited by default. Update your application to remove the dependency cycle between beans. As a last resort, it may be possible to break the cycle automatically by setting spring.main.allow-circular-references to true.

2.6版本在org.springframework.boot.SpringApplication类里增加了allowCircularReferences属性来控制循环依赖是否允许，默认值是false。

private boolean allowCircularReferences;

/**
 * Sets whether to allow circular references between beans and automatically try to
 * resolve them. Defaults to {@code false}.
 * @param allowCircularReferences if circular references are allowed
 * @since 2.6.0
 * @see AbstractAutowireCapableBeanFactory#setAllowCircularReferences(boolean)
 */
public void setAllowCircularReferences(boolean allowCircularReferences) {
	this.allowCircularReferences = allowCircularReferences;
}

所以，要保持和2.6版本之前行为一样的话，就把allowCircularReferences属性设置为true。设置可以添加配置spring.main.allow-circular-references=true，或通过SpringApplication 或 SpringApplicationBuilder 对象直接设置属性。

2.1版本禁用Bean覆盖

当出现同名bean时，会判断是否允许覆盖beanDefinition，不允许则抛出BeanDefinitionOverrideException异常。实现逻辑如下：

BeanDefinition existingDefinition = this.beanDefinitionMap.get(beanName);
if (existingDefinition != null) {
	if (!isAllowBeanDefinitionOverriding()) {
		throw new BeanDefinitionOverrideException(beanName, beanDefinition, existingDefinition);
	}
	
  // ...
	this.beanDefinitionMap.put(beanName, beanDefinition);
}

2.1版本在org.springframework.boot.SpringApplication类里增加了allowBeanDefinitionOverriding属性来控制是否允许bean覆盖，默认值是false。

private boolean allowBeanDefinitionOverriding;

/**
 * Sets if bean definition overriding, by registering a definition with the same name
 * as an existing definition, should be allowed. Defaults to {@code false}.
 * @param allowBeanDefinitionOverriding if overriding is allowed
 * @since 2.1.0
 * @see DefaultListableBeanFactory#setAllowBeanDefinitionOverriding(boolean)
 */
public void setAllowBeanDefinitionOverriding(boolean allowBeanDefinitionOverriding) {
	this.allowBeanDefinitionOverriding = allowBeanDefinitionOverriding;
}

所以，要和老版本兼容的话，就把allowBeanDefinitionOverriding属性设置为true。设置可以添加配置spring.main.allow-bean-definition-overriding=true，或通过SpringApplication 对象直接设置属性。

默认的路径匹配策略改成了PATH_PATTERN_PARSER

2.6版本之前默认策略是ANT_PATH_MATCHER，改成PATH_PATTERN_PARSER会遇到IllegalArgumentException错误。

java.lang.IllegalArgumentException: Expected lookupPath in request attribute "org.springframework.web.util.UrlPathHelper.PATH".

解决方案是将策略回滚到ANT_PATH_MATCHER：

**spring.mvc.pathmatch.matching-strategy=***ANT_PATH_MATCHER*

Spring webmvc

Cors不允许将allowedOrigins设置为*

原来为了方便，会将跨域的请求来源设置为代表允许来自所有host的请求。5.3开始增加了allowedOrigins值的校验，不允许为，否则抛出IllegalArgumentException异常。

/**
	 * Validate that when {@link #setAllowCredentials allowCredentials} is {@code true},
	 * {@link #setAllowedOrigins allowedOrigins} does not contain the special
	 * value {@code "*"} since in that case the "Access-Control-Allow-Origin"
	 * cannot be set to {@code "*"}.
	 * @throws IllegalArgumentException if the validation fails
	 * @since 5.3
	 */
	public void validateAllowCredentials() {
		if (this.allowCredentials == Boolean.TRUE &&
				this.allowedOrigins != null && this.allowedOrigins.contains(ALL)) {

			throw new IllegalArgumentException(
					"When allowCredentials is true, allowedOrigins cannot contain the special value \\"*\\" " +
							"since that cannot be set on the \\"Access-Control-Allow-Origin\\" response header. " +
							"To allow credentials to a set of origins, list them explicitly " +
							"or consider using \\"allowedOriginPatterns\\" instead.");
		}
	}

另外，5.3增加了allowedOriginPatterns属性来代替allowedOrigins的功能。所以，要允许所有host的跨域请求的话，把allowedOriginPatterns设置为*。

@Configuration
public class CorsConfig implements WebMvcConfigurer {

    @Override
    public void addCorsMappings(CorsRegistry registry) {
        registry.addMapping("/**")    // 允许跨域访问的路径
                .allowedOriginPatterns("*")    // 允许跨域访问的源
    }
}

/**
 * Alternative to {@link #setAllowedOrigins} that supports more flexible
 * origins patterns with "*" anywhere in the host name in addition to port
 * lists. Examples:
 * <ul>
 * <li>{@literal https://*.domain1.com} -- domains ending with domain1.com
 * <li>{@literal https://*.domain1.com:[8080,8081]} -- domains ending with
 * domain1.com on port 8080 or port 8081
 * <li>{@literal https://*.domain1.com:[*]} -- domains ending with
 * domain1.com on any port, including the default port
 * </ul>
 * <p>In contrast to {@link #setAllowedOrigins(List) allowedOrigins} which
 * only supports "*" and cannot be used with {@code allowCredentials}, when
 * an allowedOriginPattern is matched, the {@code Access-Control-Allow-Origin}
 * response header is set to the matched origin and not to {@code "*"} nor
 * to the pattern. Therefore allowedOriginPatterns can be used in combination
 * with {@link #setAllowCredentials} set to {@code true}.
 * <p>By default this is not set.
 * @since 5.3
 */
public CorsConfiguration setAllowedOriginPatterns(@Nullable List<String> allowedOriginPatterns) {
	if (allowedOriginPatterns == null) {
		this.allowedOriginPatterns = null;
	}
	else {
		this.allowedOriginPatterns = new ArrayList<>(allowedOriginPatterns.size());
		for (String patternValue : allowedOriginPatterns) {
			addAllowedOriginPattern(patternValue);
		}
	}
	return this;
}

静态文件是否存在的判断方式变了

5.3版本开始，ClassPathResource类型的资源文件，判断是否可读的isReadable()方法的逻辑改成了文件存在且内容不为空。当我们访问一个内容为空的资源文件时，spring返回404。

例如，访问http://localhost:8080/hello.html，spring会在/META-INF/resource、resources、static、public这几个目录下查找hello.html。如果文件放在static文件夹下，实际查找的是/static/hello.html文件。如果是jar包里，则完整的路径是这样jar:file:/opt/apps/demo.jar!/BOOT-INF/classes!/static/hello.html。

然后我们看看5.3前后版本代码，对这个文件是否可读判断的差异。

5.3版本之前，jar开头的文件直接返回true。

// 5.3之前
@Override
public boolean isReadable() {
	try {
		URL url = getURL();
    // file/vfsfile/vfs开头的url
		if (ResourceUtils.isFileURL(url)) {
			// Proceed with file system resolution
			File file = getFile();
			return (file.canRead() && !file.isDirectory());
		}
		else {
			return true;
		}
	}
	catch (IOException ex) {
		return false;
	}
}

5.3版本开始，jar开头的文件会通过con.getContentLengthLong()获取文件长度，如果是0的话就返回false。

@Override
public boolean isReadable() {
	URL url = resolveURL();
	return (url != null && checkReadable(url));
}

boolean checkReadable(URL url) {
	try {
    // file/vfsfile/vfs开头的url
		if (ResourceUtils.isFileURL(url)) {
			// Proceed with file system resolution
			File file = getFile();
			return (file.canRead() && !file.isDirectory());
		}
		else {
			// Try InputStream resolution for jar resources
			URLConnection con = url.openConnection();
			customizeConnection(con);
			if (con instanceof HttpURLConnection) {
				HttpURLConnection httpCon = (HttpURLConnection) con;
				httpCon.setRequestMethod("HEAD");
				int code = httpCon.getResponseCode();
				if (code != HttpURLConnection.HTTP_OK) {
					httpCon.disconnect();
					return false;
				}
			}
			long contentLength = con.getContentLengthLong();
			if (contentLength > 0) {
				return true;
			}
			else if (contentLength == 0) {
				// Empty file or directory -> not considered readable...
				return false;
			}
			else {
				// Fall back to stream existence: can we open the stream?
				getInputStream().close();
				return true;
			}
		}
	}
	catch (IOException ex) {
		return false;
	}
}

所以，5.3开始，静态文件不能是空文件，否则会返回404。

RequestMappingInfo#getPatternsCondition()返回null

5.3开始新增了pathPatternsCondition属性，它和patternsCondition是互斥的，所以getPatternsCondition()可能会返回null了。可以通过getActivePatternsCondition()方法获取RequestCondition对象：

/**
 * Returns either {@link #getPathPatternsCondition()} or
 * {@link #getPatternsCondition()} depending on which is not null.
 * @since 5.3
 */
@SuppressWarnings("unchecked")
public <T> RequestCondition<T> getActivePatternsCondition() {
	if (this.pathPatternsCondition != null) {
		return (RequestCondition<T>) this.pathPatternsCondition;
	}
	else if (this.patternsCondition != null) {
		return (RequestCondition<T>) this.patternsCondition;
	}
	else {
		// Already checked in the constructor...
		throw new IllegalStateException();
	}
}

引用

Bean循环引用：Spring Boot 2.6 Release Notes · spring-projects/spring-boot Wiki · GitHub

BeanDefinition覆盖：Spring Boot 2.1 Release Notes · spring-projects/spring-boot Wiki · GitHub

Spring-kafka监控文档：Spring for Apache Kafka

# spring boot # spring # 后端 # java
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