Spring Boot使用@EnableSwagger2注解启动失败求助

我是Spring框架初学者，使用@EnableSwagger2注解时应用启动失败。

我的Config类代码 #

import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.databind.ObjectMapper;
import lombok.RequiredArgsConstructor;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.swagger2.annotations.EnableSwagger2;

@EnableSwagger2
@Configuration
@RequiredArgsConstructor
public class Config {
    
    private final ObjectMapper objectMapper;

    void customizeObjectMapper() {
        objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
    }
}

报错信息 #

ApplicationContext启动失败。如需查看条件评估报告，请启用'debug'模式重新运行应用。
2023-09-28T21:12:11.549+02:00 ERROR 25124 --- [main] o.s.boot.SpringApplication : 应用启动失败

org.springframework.context.ApplicationContextException: 无法启动bean 'documentationPluginsBootstrapper'
at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:182) ~[spring-context-6.0.12.jar:6.0.12]
at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:357) ~[spring-context-6.0.12.jar:6.0.12]
at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[na:na]
at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:156) ~[spring-context-6.0.12.jar:6.0.12]
at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:124) ~[spring-context-6.0.12.jar:6.0.12]
at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:958) ~[spring-context-6.0.12.jar:6.0.12]
at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:611) ~[spring-context-6.0.12.jar:6.0.12]
at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:146) ~[spring-boot-3.1.4.jar:3.1.4]
at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737) ~[spring-boot-3.1.4.jar:3.1.4]
at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:439) ~[spring-boot-3.1.4.jar:3.1.4]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-3.1.4.jar:3.1.4]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1309) ~[spring-boot-3.1.4.jar:3.1.4]
at org.springframework.boot.SpringApplication.run(SpringApplication.java:1298) ~[spring-boot-3.1.4.jar:3.1.4]
at com.example.spring_learn_with_yt_1.SpringLearnWithYt1Application.main(SpringLearnWithYt1Application.java:10) ~[classes/:na]
Caused by: java.lang.NullPointerException: 无法调用"org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.getPatterns()"，因为"this.condition"为null
at springfox.documentation.spring.web.WebMvcPatternsRequestConditionWrapper.getPatterns(WebMvcPatternsRequestConditionWrapper.java:56) ~[springfox-spring-webmvc-3.0.0.jar:3.0.0]
at springfox.documentation.RequestHandler.sortedPaths(RequestHandler.java:113) ~[springfox-core-3.0.0.jar:3.0.0]
at springfox.documentation.spi.service.contexts.Orderings.lambda$byPatternsCondition$3(Orderings.java:89) ~[springfox-spi-3.0.0.jar:3.0.0]

问题原因及解决办法 #

原因 #

你使用的Spring Boot 3.1.4与Swagger2（springfox 3.0.0）不兼容。Spring Boot 3基于Spring 6，而springfox 3.0.0最高仅支持Spring Boot 2.7.x，两者的Web MVC组件接口、Servlet API存在差异，直接集成会触发空指针异常。

解决步骤 #

1. 替换Swagger依赖：弃用springfox，改用支持Spring Boot 3的springdoc-openapi-starter-webmvc-ui，这是当前官方推荐的API文档方案。

   • Maven依赖替换为：

     <dependency>
         <groupId>org.springdoc</groupId>
         <artifactId>springdoc-openapi-starter-webmvc-ui</artifactId>
         <version>2.2.0</version>
     </dependency>
     

   • Gradle依赖替换为：

     implementation 'org.springdoc:springdoc-openapi-starter-webmvc-ui:2.2.0'
     

2. 移除@EnableSwagger2注解：springdoc无需该注解，直接删除Config类上的@EnableSwagger2。

3. 修复ObjectMapper配置：原customizeObjectMapper方法未被Spring调用，需添加@PostConstruct注解确保初始化时执行：

   import com.fasterxml.jackson.annotation.JsonInclude;
   import com.fasterxml.jackson.databind.ObjectMapper;
   import lombok.RequiredArgsConstructor;
   import org.springframework.context.annotation.Configuration;
   import javax.annotation.PostConstruct;
   
   @Configuration
   @RequiredArgsConstructor
   public class Config {
       
       private final ObjectMapper objectMapper;
   
       @PostConstruct
       void customizeObjectMapper() {
           objectMapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);
       }
   }
   

4. 验证启动：应用启动后，访问http://localhost:8080/swagger-ui.html即可查看API文档页面。

内容的提问来源于stack exchange，提问作者Clipper