SpringBoot中的内容协商器图解

发布时间：2020-09-22 21:50:02 作者：波波维奇
来源：脚本之家阅读：175

背景

使用了restful的小伙伴对于导出这些需求本能就是拒绝的~破坏了restful的url的一致性【严格矫正不是http json就是restful 很多小伙伴都会吧暴露出一个json就直接称为restful 】

正如上文的代码生成器我们会批量生成一堆代码其中绝大部分都是RestController

  public abstract class AbstractRestController<V extends Vo, S extends So, PK extends Serializable> {
    protected Class<V> voClazz;
    @Autowired
    private Service<V, S, PK> service;
    public AbstractRestController() {
      TypeToken<V> voType = new TypeToken<V>(getClass()) {
      };
      voClazz = (Class<V>) voType.getRawType();
    }
    @PostMapping()
    @ApiOperation(value = "新建实体", notes = "")
    public Result add(@RequestBody V vo) {
      service.saveSelective(vo);
      return ResultGenerator.genSuccessResult();
    }
    @DeleteMapping("/{id}")
    @ApiOperation(value = "删除实体", notes = "")
    public Result delete(@PathVariable PK id) {
      service.deleteById(id);
      return ResultGenerator.genSuccessResult();
    }
    @PutMapping
    @ApiOperation(value = "更新实体", notes = "")
    public Result update(@RequestBody V vo) {
      service.updateByPrimaryKeySelective(vo);
      return ResultGenerator.genSuccessResult();
    }
    @GetMapping
    @ApiOperation(value = "获取实体列表", notes = "")
    public Result list(S so) {
      PageHelper.startPage(so.getCurrentPage(), so.getPageSize());
      List<V> list = service.findAll();
      PageInfo pageInfo = new PageInfo(list);
      excelExportParam();
      return ResultGenerator.genSuccessResult(pageInfo);
    }
    protected void excelExportParam() {
      ExportParams ep = new ExportParams(null, "数据");
      ExcelExportParam<V> param = new ExcelExportParam<>();
      param.setClazz(voClazz);
      param.setExcelExport(ExcelExport.NormalExcel);
      param.setExportParams(ep);
      param.setFileName("文件.xls");
      F6Static.setExcelExportParam(param);
    }
    @GetMapping("/{id}")
    @ApiOperation(value = "获取单个实体", notes = "")
    public Result detail(@PathVariable PK id) {
      V vo = service.findById(id);
      return ResultGenerator.genSuccessResult(vo);
    }
    @DeleteMapping("/batch")
    @ApiOperation(value = "批量删除实体", notes = "")
    public Result batchDelete(@RequestParam String ids) {
      service.deleteByIds(ids);
      return ResultGenerator.genSuccessResult();
    }
    @GetMapping("/batch")
    @ApiOperation(value = "批量获取实体", notes = "")
    public Result batchDetail(@RequestParam String ids) {
      List<V> vos = service.findByIds(ids);
      return ResultGenerator.genSuccessResult(vos);
    }
    @PostMapping("/batch")
    @ApiOperation(value = "批量新建实体", notes = "")
    public Result add(@RequestBody List<V> vos) {
      service.save(vos);
      return ResultGenerator.genSuccessResult();
    }
    @GetMapping("/count")
    @ApiOperation(value = "获取实体数目", notes = "")
    public Result count(@RequestBody V v) {
      int count = service.selectCount(v);
      return ResultGenerator.genSuccessResult(count);
    }

那么导出如何做呢？【其实可以理解成导出就是数据的展示不过此时结果不是json而已】

抛出一个问题那么登录登出呢？传统的方案都是login logout 那么换成restful资源的思路是啥呢？

提示：登录就是session的新建登出就是session的删除

实现

基于上述思路我们自然就想到了那么我们只需要对同一个url返回多种结果不就OK了？【pdf一个版本 json一个版本 xml一个版本 xls一个版本】

bingo！这个是内容协商器的由来

内容协商器并不是Spring创造出来的事实上这个从http头里面也能看出

SpringBoot中的内容协商器图解

1.比如给英语客户返回英语页面过于客户返回汉语页面

HTTP 协议中定义了质量值(简称 q 值)，允许客户端为每种偏好类别列出多种选项，并为每种偏好选项关联一个优先次序。

Accept-Language: en;q=0.5, fr;q=0.0, nl;q=1.0, tr;q=0.0

其中 q 值的范围从 0.0 ~ 1.0（0.0 是优先级最低的，而 1.0 是优先级最高的）。

注意，偏好的排列顺序并不重要，只有与偏好相关的 q 值才是重要的

2.那么还有其他的一些参数比如 accept-header

通常是先内容协商器有如下几种方案

1.使用Accept header:

这一种为教科书中通常描述的一种,理想中这种方式也是最好的,但如果你的资源要给用户直接通过浏览器访问(即html展现),那么由于浏览器的差异,发送上来的Accept Header头将是不一样的. 将导致服务器不知要返回什么格式的数据给你. 下面是浏览器的Accept Header

 chrome: 
    Accept:application/xml,application/xhtml+xml,textml;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5     
    firefox:
    Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8      
    IE8: 
    Accept:image/gif, image/jpeg, image/pjpeg, image/pjpeg, application/x-shockwave-flash, application/x-silverlight, application/x-ms-application, application/x-ms-xbap, application/vnd.ms-xpsdocument, application/xaml+xml, */*

2.使用扩展名

丧失了同一url多种展现的方式,但现在这种在实际环境中是使用最多的.因为更加符合程序员的审美观.

比如/user.json /user.xls /user.xml

使用参数现在很多open API是使用这种方式,比如淘宝

但是对于不同浏览器可能accept-header并不是特别统一因此许多实现选择了2 3两种方案

我们在Spring中采用上述两种方案

首先配置内容协商器

代码

@Bean
  public ViewResolver contentNegotiatingViewResolver(
      ContentNegotiationManager manager) {
    // Define the view resolvers
    ViewResolver beanNameViewResolver = new BeanNameViewResolver();
    List<ViewResolver> resolvers = Lists.newArrayList(beanNameViewResolver);
    ContentNegotiatingViewResolver resolver = new ContentNegotiatingViewResolver();
    resolver.setViewResolvers(resolvers);
    resolver.setContentNegotiationManager(manager);
    return resolver;
  }
  @Override
  public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
    configurer.favorPathExtension(true)
        .useJaf(false)
        .favorParameter(true)
        .parameterName("format")
        .ignoreAcceptHeader(true)
        .defaultContentType(MediaType.APPLICATION_JSON)
        .mediaType("json", MediaType.APPLICATION_JSON)
        .mediaType("xls", EXCEL_MEDIA_TYPE);
  }

创建对应的转换器

  private HttpMessageConverter<Object> createExcelHttpMessageConverter() {
    ExcelHttpMessageConverter excelHttpMessageConverter = new ExcelHttpMessageConverter();
    return excelHttpMessageConverter;
  }

直接使用easy-poi导出数据

  /*
   * Copyright (c) 2017. Lorem ipsum dolor sit amet, consectetur adipiscing elit.
   * Morbi non lorem porttitor neque feugiat blandit. Ut vitae ipsum eget quam lacinia accumsan.
   * Etiam sed turpis ac ipsum condimentum fringilla. Maecenas magna.
   * Proin dapibus sapien vel ante. Aliquam erat volutpat. Pellentesque sagittis ligula eget metus.
   * Vestibulum commodo. Ut rhoncus gravida arcu.
   */
  package com.f6car.base.web.converter;
  import cn.afterturn.easypoi.excel.ExcelExportUtil;
  import com.f6car.base.common.Result;
  import com.f6car.base.core.ExcelExport;
  import com.f6car.base.core.ExcelExportParam;
  import com.github.pagehelper.PageInfo;
  import com.google.common.collect.Lists;
  import org.apache.poi.ss.usermodel.Workbook;
  import org.springframework.http.HttpHeaders;
  import org.springframework.http.HttpInputMessage;
  import org.springframework.http.HttpOutputMessage;
  import org.springframework.http.MediaType;
  import org.springframework.http.converter.AbstractHttpMessageConverter;
  import org.springframework.http.converter.GenericHttpMessageConverter;
  import org.springframework.http.converter.HttpMessageNotReadableException;
  import org.springframework.http.converter.HttpMessageNotWritableException;
  import java.io.IOException;
  import java.lang.reflect.Type;
  import java.net.URLEncoder;
  import java.util.Collection;
  import java.util.Collections;
  import java.util.Map;
  import static com.f6car.base.core.F6Static.getExcelExportParam;
  /**
   * @author qixiaobo
   */
  public class ExcelHttpMessageConverter extends AbstractHttpMessageConverter<Object>
      implements GenericHttpMessageConverter<Object> {
    public static final MediaType EXCEL_MEDIA_TYPE = new MediaType("application", "vnd.ms-excel");
    public ExcelHttpMessageConverter() {
      super(EXCEL_MEDIA_TYPE);
    }
    @Override
    protected boolean supports(Class<?> clazz) {
      return false;
    }
    @Override
    protected Object readInternal(Class<?> clazz, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
      return null;
    }
    @Override
    protected void writeInternal(Object o, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {
      HttpHeaders headers = outputMessage.getHeaders();
      Collection data = getActualData((Result) o);
      ExcelExportParam excelExportParam = getExcelExportParam();
      Workbook workbook;
      switch (excelExportParam.getExcelExport()) {
        case NormalExcel:
          workbook = ExcelExportUtil.exportExcel(
              excelExportParam.getExportParams(),
              (Class<?>) excelExportParam.getClazz(),
              (Collection<?>) data);
          break;
        case MapExcel:
          workbook = ExcelExportUtil.exportExcel(
              excelExportParam.getExportParams(),
              excelExportParam.getExcelExportEntities(),
              (Collection<? extends Map<?, ?>>) data);
          break;
        case BigExcel:
        case MapExcelGraph:
        case PDFTemplate:
        case TemplateExcel:
        case TemplateWord:
        default:
          throw new RuntimeException();
      }
      if (workbook != null) {
        if (excelExportParam.getFileName() != null) {
          String codedFileName = URLEncoder.encode(excelExportParam.getFileName(), "UTF8");
          headers.setContentDispositionFormData("attachment", codedFileName);
        }
        workbook.write(outputMessage.getBody());
      }
    }
    private Collection getActualData(Result r) {
      if (r != null && r.getData() != null) {
        Object data = r.getData();
        if (data instanceof PageInfo) {
          return ((PageInfo) data).getList();
        } else if (!(data instanceof Collection)) {
          data = Lists.newArrayList(data);
        } else {
          return (Collection) data;
        }
      }
      return Collections.emptyList();
    }
    @Override
    public boolean canRead(Type type, Class<?> contextClass, MediaType mediaType) {
      //不支持excel
      return false;
    }
    @Override
    public Object read(Type type, Class<?> contextClass, HttpInputMessage inputMessage) throws IOException, HttpMessageNotReadableException {
      return null;
    }
    @Override
    public boolean canWrite(Type type, Class<?> clazz, MediaType mediaType) {
      return super.canWrite(mediaType) && clazz == Result.class && support();
    }
    private boolean support() {
      ExcelExportParam param = getExcelExportParam();
      if (param == null || param.getExcelExport() == null || param.getExportParams() == null) {
        return false;
      }
      if (param.getExcelExport() == ExcelExport.NormalExcel) {
        return true;
      } else {
        logger.warn(param.getExcelExport() + " not supprot now!");
        return false;
      }
    }
    @Override
    public void write(Object o, Type type, MediaType contentType, HttpOutputMessage outputMessage) throws IOException, HttpMessageNotWritableException {
      super.write(o, contentType, outputMessage);
    }
  }

暂时只是针对导出因此在使用的时候如下

 @GetMapping
  @ApiOperation(value = "获取实体列表", notes = "")
  public Result list(S so) {
    PageHelper.startPage(so.getCurrentPage(), so.getPageSize());
    List<V> list = service.findAll();
    PageInfo pageInfo = new PageInfo(list);
    excelExportParam();
    return ResultGenerator.genSuccessResult(pageInfo);
  }
  protected void excelExportParam() {
    ExportParams ep = new ExportParams(null, "数据");
    ExcelExportParam<V> param = new ExcelExportParam<>();
    param.setClazz(voClazz);
    param.setExcelExport(ExcelExport.NormalExcel);
    param.setExportParams(ep);
    param.setFileName("文件.xls");
    F6Static.setExcelExportParam(param);
  }

当我们访问时如下

http://127.0.0.1:8079/zeus/user

SpringBoot中的内容协商器图解

 {
  "code": 200,
  "data": {
  "endRow": 10,
  "firstPage": 1,
  "hasNextPage": true,
  "hasPreviousPage": false,
  "isFirstPage": true,
  "isLastPage": false,
  "lastPage": 8,
  "list": [
  {
  "cellPhone": "13857445502",
  "idEmployee": 24201883434352650,
  "idOwnOrg": 23993199378825296,
  "idRole": 88,
  "idWxbStation": "332",
  "idWxbUser": "207",
  "isAdmin": 1,
  "isDel": 0,
  "isGuideOpen": 0,
  "limitMac": 0,
  "openid": "",
  "password": "96e79218965eb72c92a549dd5a330112",
  "pkId": 23993199378825296,
  "username": "lingweiqiche"
  },
  {
  "cellPhone": "",
  "idEmployee": 0,
  "idOwnOrg": 9999,
  "idRole": 4,
  "idWxbStation": "",
  "idWxbUser": "",
  "isAdmin": 0,
  "isDel": 0,
  "isGuideOpen": 0,
  "limitMac": 0,
  "openid": "",
  "password": "96e79218965eb72c92a549dd5a330112",
  "pkId": 24201883434356532,
  "username": "007"
  },
  {
  "cellPhone": "15715139000",
  "idEmployee": 24351585207523460,
  "idOwnOrg": 24201883434357600,
  "idRole": 89,
  "idWxbStation": "540",
  "idWxbUser": "298",
  "isAdmin": 1,
  "isDel": 0,
  "isGuideOpen": 0,
  "limitMac": 0,
  "openid": "",
  "password": "96e79218965eb72c92a549dd5a330112",
  "pkId": 24201883434357600,
  "username": "15715139000"
  },
  {
  "cellPhone": "",
  "idEmployee": 0,
  "idOwnOrg": 24201883434357600,
  "idRole": 216,
  "idWxbStation": "",
  "idWxbUser": "",
  "isAdmin": 0,
  "isDel": 0,
  "isGuideOpen": 0,
  "limitMac": 0,
  "openid": "",
  "password": "96e79218965eb72c92a549dd5a330112",
  "pkId": 24201883434357920,
  "username": "sunlingli"
  },
  {
  "cellPhone": "",
  "idEmployee": 24351585207425676,
  "idOwnOrg": 24201883434359384,
  "idRole": 90,
  "idWxbStation": "348",
  "idWxbUser": "227",
  "isAdmin": 1,
  "isDel": 0,
  "isGuideOpen": 0,
  "limitMac": 0,
  "openid": "opzUDs_v13WE500kxYMj6Xg_gFeE",
  "password": "96e79218965eb72c92a549dd5a330112",
  "pkId": 24201883434359388,
  "username": "15952920979"
  },
  {
  "cellPhone": "",
  "idEmployee": 0,
  "idOwnOrg": 24201883434359790,
  "idRole": 91,
  "idWxbStation": "315",
  "idWxbUser": "175",
  "isAdmin": 1,
  "isDel": 0,
  "isGuideOpen": 0,
  "limitMac": 0,
  "openid": "",
  "password": "96e79218965eb72c92a549dd5a330112",
  "pkId": 24201883434359790,
  "username": "13809056211"
  },
  {
  "cellPhone": "18903885585",
  "idEmployee": 24201883434366164,
  "idOwnOrg": 24201883434359890,
  "idRole": 92,
  "idWxbStation": "317",
  "idWxbUser": "178",
  "isAdmin": 1,
  "isDel": 0,
  "isGuideOpen": 0,
  "limitMac": 0,
  "openid": "",
  "password": "96e79218965eb72c92a549dd5a330112",
  "pkId": 24201883434359892,
  "username": "18903885585"
  },
  {
  "cellPhone": "",
  "idEmployee": 24351585207425668,
  "idOwnOrg": 24201883434359924,
  "idRole": 93,
  "idWxbStation": "318",
  "idWxbUser": "179",
  "isAdmin": 1,
  "isDel": 0,
  "isGuideOpen": 0,
  "limitMac": 0,
  "openid": "",
  "password": "96e79218965eb72c92a549dd5a330112",
  "pkId": 24201883434359930,
  "username": "13372299595"
  },
  {
  "cellPhone": "",
  "idEmployee": 0,
  "idOwnOrg": 24201883434360052,
  "idRole": 94,
  "idWxbStation": "321",
  "idWxbUser": "188",
  "isAdmin": 1,
  "isDel": 0,
  "isGuideOpen": 0,
  "limitMac": 0,
  "openid": "",
  "password": "96e79218965eb72c92a549dd5a330112",
  "pkId": 24201883434360052,
  "username": "15221250005"
  },
  {
  "cellPhone": "",
  "idEmployee": 0,
  "idOwnOrg": 24201883434360070,
  "idRole": 95,
  "idWxbStation": "325",
  "idWxbUser": "198",
  "isAdmin": 1,
  "isDel": 0,
  "isGuideOpen": 0,
  "limitMac": 0,
  "openid": "",
  "password": "96e79218965eb72c92a549dd5a330112",
  "pkId": 24201883434360070,
  "username": "13837251167"
  }
  ],
  "navigateFirstPage": 1,
  "navigateLastPage": 8,
  "navigatePages": 8,
  "navigatepageNums": [
  1,
  2,
  3,
  4,
  5,
  6,
  7,
  8
  ],
  "nextPage": 2,
  "orderBy": "",
  "pageNum": 1,
  "pageSize": 10,
  "pages": 102,
  "prePage": 0,
  "size": 10,
  "startRow": 1,
  "total": 1012
  },
  "message": "SUCCESS"
  }

当访问http://127.0.0.1:8079/zeus/user?format=xls 或者http://127.0.0.1:8079/zeus/user.xls

如下效果

SpringBoot中的内容协商器图解