Spring boot 2.6使用Swagger2提示“documentationPluginsBootstrapper”错误

问题说明

Spring boot 版本：2.6.0
Swagger版本：2.9.2

在整合的时候IDE生成的时候提示错误，错误信息如下：

org.springframework.context.ApplicationContextException: Failed to start bean 'documentationPluginsBootstrapper'; nested exception is java.lang.NullPointerException: Cannot invoke "org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.toString()" because the return value of "springfox.documentation.spi.service.contexts.Orderings.patternsCondition(springfox.documentation.RequestHandler)" is null
	at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:181) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.context.support.DefaultLifecycleProcessor.access$200(DefaultLifecycleProcessor.java:54) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.context.support.DefaultLifecycleProcessor$LifecycleGroup.start(DefaultLifecycleProcessor.java:356) ~[spring-context-5.3.13.jar:5.3.13]
	at java.base/java.lang.Iterable.forEach(Iterable.java:75) ~[na:na]
	at org.springframework.context.support.DefaultLifecycleProcessor.startBeans(DefaultLifecycleProcessor.java:155) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.context.support.DefaultLifecycleProcessor.onRefresh(DefaultLifecycleProcessor.java:123) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.context.support.AbstractApplicationContext.finishRefresh(AbstractApplicationContext.java:935) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:586) ~[spring-context-5.3.13.jar:5.3.13]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:145) ~[spring-boot-2.6.0.jar:2.6.0]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:730) ~[spring-boot-2.6.0.jar:2.6.0]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:412) ~[spring-boot-2.6.0.jar:2.6.0]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:302) ~[spring-boot-2.6.0.jar:2.6.0]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1301) ~[spring-boot-2.6.0.jar:2.6.0]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1290) ~[spring-boot-2.6.0.jar:2.6.0]
	at com.ityouzi.test3.Test3Application.main(Test3Application.java:12) ~[classes/:na]
Caused by: java.lang.NullPointerException: Cannot invoke "org.springframework.web.servlet.mvc.condition.PatternsRequestCondition.toString()" because the return value of "springfox.documentation.spi.service.contexts.Orderings.patternsCondition(springfox.documentation.RequestHandler)" is null
	at springfox.documentation.spi.service.contexts.Orderings$8.compare(Orderings.java:112) ~[springfox-spi-2.9.2.jar:null]
	at springfox.documentation.spi.service.contexts.Orderings$8.compare(Orderings.java:109) ~[springfox-spi-2.9.2.jar:null]
	at com.google.common.collect.ComparatorOrdering.compare(ComparatorOrdering.java:37) ~[guava-20.0.jar:na]
	at java.base/java.util.TimSort.countRunAndMakeAscending(TimSort.java:355) ~[na:na]
	at java.base/java.util.TimSort.sort(TimSort.java:220) ~[na:na]
	at java.base/java.util.Arrays.sort(Arrays.java:1232) ~[na:na]
	at com.google.common.collect.Ordering.sortedCopy(Ordering.java:855) ~[guava-20.0.jar:na]
	at springfox.documentation.spring.web.plugins.WebMvcRequestHandlerProvider.requestHandlers(WebMvcRequestHandlerProvider.java:57) ~[springfox-spring-web-2.9.2.jar:null]
	at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper$2.apply(DocumentationPluginsBootstrapper.java:138) ~[springfox-spring-web-2.9.2.jar:null]
	at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper$2.apply(DocumentationPluginsBootstrapper.java:135) ~[springfox-spring-web-2.9.2.jar:null]
	at com.google.common.collect.Iterators$7.transform(Iterators.java:750) ~[guava-20.0.jar:na]
	at com.google.common.collect.TransformedIterator.next(TransformedIterator.java:47) ~[guava-20.0.jar:na]
	at com.google.common.collect.TransformedIterator.next(TransformedIterator.java:47) ~[guava-20.0.jar:na]
	at com.google.common.collect.MultitransformedIterator.hasNext(MultitransformedIterator.java:52) ~[guava-20.0.jar:na]
	at com.google.common.collect.MultitransformedIterator.hasNext(MultitransformedIterator.java:50) ~[guava-20.0.jar:na]
	at com.google.common.collect.ImmutableList.copyOf(ImmutableList.java:249) ~[guava-20.0.jar:na]
	at com.google.common.collect.ImmutableList.copyOf(ImmutableList.java:209) ~[guava-20.0.jar:na]
	at com.google.common.collect.FluentIterable.toList(FluentIterable.java:614) ~[guava-20.0.jar:na]
	at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.defaultContextBuilder(DocumentationPluginsBootstrapper.java:111) ~[springfox-spring-web-2.9.2.jar:null]
	at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.buildContext(DocumentationPluginsBootstrapper.java:96) ~[springfox-spring-web-2.9.2.jar:null]
	at springfox.documentation.spring.web.plugins.DocumentationPluginsBootstrapper.start(DocumentationPluginsBootstrapper.java:167) ~[springfox-spring-web-2.9.2.jar:null]
	at org.springframework.context.support.DefaultLifecycleProcessor.doStart(DefaultLifecycleProcessor.java:178) ~[spring-context-5.3.13.jar:5.3.13]
	... 14 common frames omitted

解决方案

在application文件中增加配置，配置内容如下：

spring:
  mvc:
    pathmatch:
      matching-strategy: ant_path_matcher

我的配置文件格式是 yml

添加好配置以后，重新生成就没有错误了。

官方的解释说明：

如Spring Boot 2.6发行说明中所述，您可以通过在application.properties文件中将Spring.mvc.pathmatch.matching-strategy设置为ant path matcher来恢复Springfox假定将使用的配置。请注意，只有在不使用Spring Boot的执行器时，此功能才起作用。无论配置的匹配策略如何，执行器始终使用基于路径模式的解析。如果您想在Spring Boot 2.6及更高版本中将其与执行器一起使用，则需要对Springfox进行更改。

完整参考代码

下面我将整合的完整代码贴出来，方便大家参考，只是简单的示例，所以代码规范和完整性上有所欠缺，望见谅。

1、导入pom

   <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.9.2</version>
        </dependency>

        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>2.9.2</version>
        </dependency>

        <dependency>
            <groupId>com.github.xiaoymin</groupId>
            <artifactId>swagger-bootstrap-ui</artifactId>
            <version>1.9.6</version>
        </dependency>

swagger-bootstrap-ui：这个包是用来修改swagger默认的显示样式的，如果不想修改界面样式可不导入。

2、添加配置文件，将swagger的配置注入到容器中

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.builders.ApiInfoBuilder;
import springfox.documentation.builders.PathSelectors;
import springfox.documentation.builders.RequestHandlerSelectors;
import springfox.documentation.service.ApiInfo;
import springfox.documentation.service.Contact;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;
import springfox.documentation.swagger2.annotations.EnableSwagger2;

/**
 * Swagger2的配置
 */
@Configuration
@EnableSwagger2
public class SwaggerConfig {

    @Bean
    public Docket createRestApi() {
        return new Docket(DocumentationType.SWAGGER_2)
                .groupName("用户模块")  //模块名称
                .apiInfo(apiInfo())
                .select()
                .apis(RequestHandlerSelectors.basePackage("com.ityouzi.test3.controller"))  //扫描的控制器路径
                .paths(PathSelectors.any())
                .build();
    }

    /**
     * 获取接口文档的一些信息
     * @return
     */
    private ApiInfo apiInfo() {
        return new ApiInfoBuilder()
                .title("xxx项目开发接口文档")    //接口文档标题
                .description("此文档仅供开发技术组领导、开发人员使用")   //描述
                .termsOfServiceUrl("http://www.baidu.com/")   //相关的网址
                .contact(new Contact("后端开发","http://www.xxx.com/","XXXXXX7805@qq.com"))    //作者  邮箱等
                .version("1.0")  //版本号
                .build();
    }
}

里面的一些信息可根据自己的情况修改，比如作者、版本等等，详见中文的注释。

3、控制器上增加注解

import com.ityouzi.test3.entity.HelpCategory;
import com.ityouzi.test3.service.IHelpCategoryService;
import io.swagger.annotations.Api;
import io.swagger.annotations.ApiImplicitParam;
import io.swagger.annotations.ApiImplicitParams;
import io.swagger.annotations.ApiOperation;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.*;
import org.springframework.web.servlet.ModelAndView;

import java.util.List;

@RestController
@RequestMapping("/help")
@Api(tags = "帮助信息管理")
public class HelpController {

    @Autowired
    private IHelpCategoryService helpCategoryService;

    @GetMapping("/queryAll")
    @ApiOperation(value = "查询所有的帮助分类")
    public String queryAll()
    {
        List<HelpCategory> list = this.helpCategoryService.list();
        return list.toString();
    }

    @GetMapping("/detail")
    @ApiOperation(value = "根据Id查询详情信息")
    @ApiImplicitParams({@ApiImplicitParam(name = "id",dataType = "long",value = "帮助信息Id",required = true)})
    public String detail(Long id)
    {
        List<HelpCategory> list = this.helpCategoryService.list();
        return list.toString();
    }

}

上面只是一些简单的注解，更得多注解推荐观看视频：https://www.bilibili.com/video/BV12p4y187Dj?p=54

4、修改全局的配置文件，不修改会导致错误，就上面出现的问题

在application文件中增加配置，配置内容如下，我的配置文件格式是 yml：

spring:
  mvc:
    pathmatch:
      matching-strategy: ant_path_matcher

5、开始执行

IDE上启动网站。

如果没有替换过Swagger的样式，则访问的域名是：http://localhost:8080/swagger-ui.html，前面的域名根据自己项目的配置来。
如果替换过默认的样式（swagger-bootstrap-ui），则访问的域名是：http://localhost:8080/dochtml，前面的域名根据自己项目的配置来。

效果图如下：