使用 Spring Boot 2.4.1

问题描述

我正在使用 Spring Boot 2.4.1 和 Eureka 开发应用程序。我成功启动了 Eureka 服务器，但是使用 Eureka 客户端时出现以下错误：

Caused by: java.lang.classNotFoundException: com.sun.jersey.client.apache4.ApacheHttpClient4
    at java.base/jdk.internal.loader.BuiltinClassLoader.loadClass(BuiltinClassLoader.java:606) ~[na:na]
    at java.base/jdk.internal.loader.ClassLoaders$AppClassLoader.loadClass(ClassLoaders.java:168) ~[na:na]
    at java.base/java.lang.classLoader.loadClass(ClassLoader.java:522) ~[na:na]
    ... 55 common frames omitted
...
Caused by: java.lang.NullPointerException: Cannot invoke "org.springframework.cloud.netflix.eureka.CloudEurekaClient.getApplications()" because the return value of "org.springframework.cloud.netflix.eureka.serviceregistry.EurekaRegistration.getEurekaClient()" is null
    at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaServiceRegistry.maybeInitializeClient(EurekaServiceRegistry.java:54) ~[spring-cloud-netflix-eureka-client-3.0.0.jar:3.0.0]
    at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaServiceRegistry.register(EurekaServiceRegistry.java:38) ~[spring-cloud-netflix-eureka-client-3.0.0.jar:3.0.0]
    at org.springframework.cloud.netflix.eureka.serviceregistry.EurekaAutoServiceRegistration.start(EurekaAutoServiceRegistration.java:83) ~[spring-cloud-netflix-eureka-client-3.0.0.jar:3.0.0]
    at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178) ~[spring-context-5.3.2.jar:5.3.2]

pom.xml 如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.4.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <java.version>15</java.version>
        <spring-cloud.version>2020.0.0</spring-cloud.version>
    </properties>

    <groupId>some.group</groupId>
    <artifactId>some-artefact</artifactId>
    <version>1.0</version>
    <name>some-name</name>
    <description>some-description</description>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

以下是application.yml：

spring:
  application:
    name: @project.artifactId@

logging:
  file.name: ../logs/@project.artifactId@.log
  file.max-size: 10MB

server:
  port: 8080

还有主类：

@SpringBootApplication
@ComponentScan("com.something")
@EnablediscoveryClient
public class SpigaConnectorServiceApplication {

    public static void main(String[] args) {
        SpringApplication.run(SpigaConnectorServiceApplication.class,args);
    }

    @RestController
    class ServiceInstanceRestController {

        @Autowired
        private discoveryClient discoveryClient;

        @RequestMapping("/service-instances/{applicationName}")
        public List<ServiceInstance> serviceInstancesByApplicationName(
                @PathVariable String applicationName) {
            return this.discoveryClient.getInstances(applicationName);
        }
    }
}

以下是服务器pom：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.7.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <java.version>15</java.version>
        <spring-cloud.version>Hoxton.SR1</spring-cloud.version>
    </properties>

    <groupId>com.ptesa.cloud</groupId>
    <artifactId>pt-eureka-server</artifactId>
    <version>1.0</version>
    <name>pt-eureka-server</name>
    <description>Registry and discovery of services</description>
    <packaging>jar</packaging>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

服务器的application.yml：

server:
  port: 8761
eureka:
  client:
    registerWithEureka: false
    fetchRegistry: false

以及启动服务器的类：

@EnableEurekaServer
@SpringBootApplication
public class EurekaServerApplication {

    public static void main(String[] args) {
        SpringApplication.run(com.ptesa.cloud.EurekaServerApplication.class);
    }

}

使用 Spring Boot 版本 2.3.7.RELEASE 时我没有这个问题。应用程序几乎正常启动。只需收到以下警告：

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.thoughtworks.xstream.core.util.Fields (file:/C:/Users/Jucaalpa/.m2/repository/com/thoughtworks/xstream/xstream/1.4.11.1/xstream-1.4.11.1.jar) to field java.util.TreeMap.comparator
WARNING: Please consider reporting this to the maintainers of com.thoughtworks.xstream.core.util.Fields
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

有没有办法用 Spring Boot 2.4.1 运行 Eureka 客户端。由于兼容性问题，您认为使用 Spring Boot 2.3.7 会更好吗？

谢谢。

解决方法

发现添加如下依赖，问题不存在。

<dependency>
    <groupId>com.sun.jersey.contribs</groupId>
    <artifactId>jersey-apache-client4</artifactId>
    <version>1.19.4</version>
</dependency>

在客户端yaml文件中，添加如下配置

eureka:
  client:
    register-with-eureka: true
    fetch-registry: true
    service-url:
      defaultZone: http://localhost:8761/eureka/
  instance:
    hostname: localhost

java java maven netflix-eureka spring-boot spring-cloud