1 public class SpringFormEncoder extends FormEncoder
 2 {
 3
 4     public SpringFormEncoder()
 5     {
 6         this(((Encoder) (new feign.codec.Encoder.Default())));
 7     }
 8
 9     public SpringFormEncoder(Encoder delegate)
10     {
11         super(delegate);//调用父类的构造方法
12         MultipartFormContentProcessor processor = (MultipartFormContentProcessor)getContentProcessor(ContentType.MULTIPART);
13         processor.addWriter(new SpringSingleMultipartFileWriter());
14         processor.addWriter(new SpringManyMultipartFilesWriter());
15     }
16
17     public void encode(Object object, Type bodyType, RequestTemplate template)
18         throws EncodeException
19     {
20         if(!bodyType.equals(org/springframework/web/multipart/MultipartFile))
21         {
22             super.encode(object, bodyType, template);//调用FormEncoder对应方法
23             return;
24         } else
25         {
26             MultipartFile file = (MultipartFile)object;
27             java.util.Map data = Collections.singletonMap(file.getName(), object);
28             super.encode(data, MAP_STRING_WILDCARD, template);
29             return;
30         }
31     }
32 }

 1 public FormEncoder()
 2     {
 3         this(((Encoder) (new feign.codec.Encoder.Default())));
 4     }
 5
 6     public FormEncoder(Encoder delegate)
 7     {
 8         _flddelegate = delegate;
 9         List list = Arrays.asList(new ContentProcessor[] {
10             new MultipartFormContentProcessor(delegate), new UrlencodedFormContentProcessor()
11         });
12         processors = new HashMap(list.size(), 1.0F);
13         ContentProcessor processor;
14         for(Iterator iterator = list.iterator(); iterator.hasNext(); processors.put(processor.getSupportedContentType(), processor))
15             processor = (ContentProcessor)iterator.next();
16
17     }
18
19     public void encode(Object object, Type bodyType, RequestTemplate template)
20         throws EncodeException
21     {
22         String contentTypeValue = getContentTypeValue(template.headers());//这里会去到@PostMapping中consumes的值，所以参数需要传对象时指定一下consumes
23         ContentType contentType = ContentType.of(contentTypeValue);//为啥指定consumes，是因为不指定就是application/x-www-form-urlencoded，而且processors中也包含，为啥包含见FormEncoder的构造函数
24         if(!MAP_STRING_WILDCARD.equals(bodyType) || !processors.containsKey(contentType))
25         {
26             _flddelegate.encode(object, bodyType, template);//_flddelegate是啥呢，是SpringFormEncoder传递过来，也就是new Encoder.Default()
27             return;
28         }
29         Charset charset = getCharset(contentTypeValue);
30         Map data = (Map)object;
31         try
32         {
33             ((ContentProcessor)processors.get(contentType)).process(template, charset, data);
34         }
35         catch(Exception ex)
36         {
37             throw new EncodeException(ex.getMessage());
38         }
39     }

 1 public interface Encoder
 2 {
 3     public static class Default
 4         implements Encoder
 5     {
 6
 7         public void encode(Object object, Type bodyType, RequestTemplate template)
 8         {
 9             if(bodyType == java/lang/String)
10                 template.body(object.toString());
11             else
12             if(bodyType == [B)
13                 template.body((byte[])(byte[])object, null);
14             else
15             if(object != null)//当我们用对象传递参数的时候，会走这里
16                 throw new EncodeException(String.format("%s is not a type supported by this encoder.", new Object[] {
17                     object.getClass()
18                 }));
19         }
20
21         public Default()
22         {
23         }
24     }
25
26
27     public abstract void encode(Object obj, Type type, RequestTemplate requesttemplate)
28         throws EncodeException;
29
30     public static final Type MAP_STRING_WILDCARD = Util.MAP_STRING_WILDCARD;
31
32 }

 1 @Configuration
 2 class MultipartSupportConfig {
 3     @Autowired
 4     private ObjectFactory<HttpMessageConverters> messageConverters;
 5
 6     @Bean
 7     public Encoder feignFormEncoder() {
 8         return new SpringFormEncoder(new SpringEncoder(messageConverters));
 9     }
10  }