前言

最近使用了最新版本的springfox-swagger2做api接口文档；但是发现之前的position已过时，故想着修改springfox的java代码来实现按position排序~

依赖信息

        <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>

代码分析

我们启动工程后，访问swagger-ui.html能看到获取api信息的url地址:http://localhost:8080/cms/v2/api-docs
我们使用idea搜索（ctrl+shitf+F）一下api-docs，范围选择scope会发现一个Swagger2Controller的类。打开，可见到如下代码：

  @RequestMapping(
      value = DEFAULT_URL,
      method = RequestMethod.GET,
      produces = { APPLICATION_JSON_VALUE, HAL_MEDIA_TYPE })
  @PropertySourcedMapping(
      value = "${springfox.documentation.swagger.v2.path}",
      propertyKey = "springfox.documentation.swagger.v2.path")
  @ResponseBody
  public ResponseEntity<Json> getDocumentation(
      @RequestParam(value = "group", required = false) String swaggerGroup,
      HttpServletRequest servletRequest) {

    String groupName = Optional.fromNullable(swaggerGroup).or(Docket.DEFAULT_GROUP_NAME);
    Documentation documentation = documentationCache.documentationByGroup(groupName);
    if (documentation == null) {
      LOGGER.warn("Unable to find specification for group {}", groupName);
      return new ResponseEntity<Json>(HttpStatus.NOT_FOUND);
    }
    Swagger swagger = mapper.mapDocumentation(documentation);
    UriComponents uriComponents = componentsFrom(servletRequest, swagger.getBasePath());
    swagger.basePath(Strings.isNullOrEmpty(uriComponents.getPath()) ? "/" : uriComponents.getPath());
    if (isNullOrEmpty(swagger.getHost())) {
      swagger.host(hostName(uriComponents));
    }
    return new ResponseEntity<Json>(jsonSerializer.toJson(swagger), HttpStatus.OK);
  }

从代码上看，我们可了解到，前端swagger-ui所需的api接口信息都是由Swagger对象提供。我们进入此方法

Swagger swagger = mapper.mapDocumentation(documentation);
可看到此方法的实现代码如下：

public Swagger mapDocumentation(Documentation from) {
        if ( from == null ) {
            return null;
        }

        Swagger swagger = new Swagger();

        swagger.setVendorExtensions( vendorExtensionsMapper.mapExtensions( from.getVendorExtensions() ) );
        swagger.setSchemes( mapSchemes( from.getSchemes() ) );
        swagger.setPaths( mapApiListings( from.getApiListings() ) );
        swagger.setHost( from.getHost() );
        swagger.setDefinitions( modelMapper.modelsFromApiListings( from.getApiListings() ) );
        swagger.setSecurityDefinitions( securityMapper.toSecuritySchemeDefinitions( from.getResourceListing() ) );
        ApiInfo info = fromResourceListingInfo( from );
        if ( info != null ) {
            swagger.setInfo( mapApiInfo( info ) );
        }
        swagger.setBasePath( from.getBasePath() );
        swagger.setTags( tagSetToTagList( from.getTags() ) );
        List<String> list2 = from.getConsumes();
        if ( list2 != null ) {
            swagger.setConsumes( new ArrayList<String>( list2 ) );
        }
        else {
            swagger.setConsumes( null );
        }
        List<String> list3 = from.getProduces();
        if ( list3 != null ) {
            swagger.setProduces( new ArrayList<String>( list3 ) );
        }
        else {
            swagger.setProduces( null );
        }

        return swagger;
    }

从代码上的字面看，可以估计到api的请求的url等信息主要由下面的方法得到。

swagger.setPaths( mapApiListings( from.getApiListings() ) );
为了查看具体的信息，我们先在此处打个断点。运行工程看看swagger paths里面的数据信息。某次执行后，debug的信息如下

paths = {TreeMap@7288}  size = 4
 0 = {TreeMap$Entry@7292} "/generator.cmd/a/generator" -> 
  key = "/generator.cmd/a/generator"
  value = {Path@7297} 
 1 = {TreeMap$Entry@7293} "/generator.cmd/b/generator" -> 
  key = "/generator.cmd/b/generator"
  value = {Path@7299} 
 2 = {TreeMap$Entry@7294} "/generator.cmd/c/generator" -> 
  key = "/generator.cmd/c/generator"
  value = {Path@7301} 
 3 = {TreeMap$Entry@7295} "/generator.cmd/generator" -> 
  key = "/generator.cmd/generator"
  value = {Path@7303} 

由此可见，在生成sagger信息的时候，就已经默认使用了TreeMap方法来排序；故返回给前端的信息都是由url的path排序的。所以为实现按position排序，估计可以由此着手修改。
为此我们重写该方法：

package xxx.swagger;

import com.google.common.base.Optional;
import com.google.common.collect.LinkedListMultimap;
import com.google.common.collect.Multimap;
import io.swagger.models.Operation;
import io.swagger.models.Path;
import io.swagger.models.Swagger;
import io.swagger.models.Tag;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.context.annotation.Primary;
import org.springframework.stereotype.Component;
import springfox.documentation.service.ApiDescription;
import springfox.documentation.service.ApiListing;
import springfox.documentation.service.Documentation;
import springfox.documentation.swagger2.mappers.ServiceModelToSwagger2MapperImpl;

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;

import static springfox.documentation.builders.BuilderDefaults.nullToEmptyList;

@Component
@Primary
public class ServiceModelToSwagger2MapperImplExt extends ServiceModelToSwagger2MapperImpl {

    private  static final Logger logger = LoggerFactory.getLogger(ServiceModelToSwagger2MapperImplExt.class);

    @Override
    public Swagger mapDocumentation(Documentation from) {
        Swagger swagger = super.mapDocumentation(from);
        swagger.setPaths( mapApiListings( from.getApiListings() ) );
        // 可自定义tag的排序
        // List<Tag> tags = swagger.getTags();
        // Collections.sort(tags, new Comparator<Tag>() {
        //     @Override
        //     public int compare(Tag left, Tag right) {
        //         String leftTag = left.getName().split("、")[0];
        //         String rightTag = right.getName().split("、")[0];
        //         int leftNum = 0;
        //         int rightNum = 0;
        //         try{
        //             leftNum = Integer.parseInt(leftTag);
        //             rightNum = Integer.parseInt(rightTag);
        //         }catch (Exception e){}
        //         int position = Integer.compare(leftNum, rightNum);
        //         return position;
        //     }
        // });
        // swagger.setTags(tags);
        return swagger;
    }

    protected Map<String, Path> mapApiListings(Multimap<String, ApiListing> apiListings) {
        Map<String, Path> paths = new LinkedHashMap<>();
        Multimap<String, ApiListing> apiListingMap = LinkedListMultimap.create();
        Iterator iter = apiListings.entries().iterator();
        while(iter.hasNext())
        {
            Map.Entry<String, ApiListing> entry = (Map.Entry<String, ApiListing>)iter.next();
            ApiListing apis =  entry.getValue();
            List<ApiDescription> apiDesc = apis.getApis();
            List<ApiDescription> newApi = new ArrayList<>();
            for(ApiDescription a:apiDesc){
                newApi.add(a);
            }
            Collections.sort(newApi, new Comparator<ApiDescription>() {
                @Override
                public int compare(ApiDescription left, ApiDescription right) {
                    int leftPos = left.getOperations().size() == 1 ? left.getOperations().get(0).getPosition() : 0;
                    int rightPos = right.getOperations().size() == 1 ? right.getOperations().get(0).getPosition() : 0;

                    int position = Integer.compare(leftPos, rightPos);
                    if(position == 0) {
                        position = left.getPath().compareTo(right.getPath());
                    }

                    return position;
                }
            });
            try {
                //因ApiListing的属性都是final故需要通过反射来修改值
                ModifyFinalUtils.modify(apis, "apis", newApi);
            } catch (Exception e) {
                e.printStackTrace();
            }
            apiListingMap.put(entry.getKey(),apis);
        }

        for (ApiListing each : apiListingMap.values()) {
            for (ApiDescription api : each.getApis()) {
                paths.put(api.getPath(), mapOperations(api, Optional.fromNullable(paths.get(api.getPath()))));
            }
        }
        return paths;
    }

    private Path mapOperations(ApiDescription api, Optional<Path> existingPath) {
        Path path = existingPath.or(new Path());
        for (springfox.documentation.service.Operation each : nullToEmptyList(api.getOperations())) {
            Operation operation = mapOperation(each);
            path.set(each.getMethod().toString().toLowerCase(), operation);
        }
        return path;
    }
}

public class ModifyFinalUtils {
    public static void modify(Object object, String fieldName, Object newFieldValue) throws Exception {
        Field field = object.getClass().getDeclaredField(fieldName);

        Field modifiersField = Field.class.getDeclaredField("modifiers");
        modifiersField.setAccessible(true); //Field 的 modifiers 是私有的
        modifiersField.setInt(field, field.getModifiers() & ~Modifier.FINAL);

        if(!field.isAccessible()) {
            field.setAccessible(true);
        }

        field.set(object, newFieldValue);
    }
}

执行后，我们debug可以得到以下信息

paths = {LinkedHashMap@7364}  size = 4
 0 = {LinkedHashMap$Entry@7370} "/generator.cmd/b/generator" -> 
  key = "/generator.cmd/b/generator"
  value = {Path@7374} 
 1 = {LinkedHashMap$Entry@7371} "/generator.cmd/generator" -> 
  key = "/generator.cmd/generator"
  value = {Path@7375} 
 2 = {LinkedHashMap$Entry@7372} "/generator.cmd/c/generator" -> 
  key = "/generator.cmd/c/generator"
  value = {Path@7376} 
 3 = {LinkedHashMap$Entry@7373} "/generator.cmd/a/generator" -> 
  key = "/generator.cmd/a/generator"
  value = {Path@7377} 

看来，按position排序已经生效。