org.apache.dubbo.metadata.definition.builder.MapTypeBuilder#build写死actualTypeArgsLength==2？？

[tiger822]

Environment

• Dubbo version: 3.0.3
• Operating System version: windows10
• Java version: 11

Steps to reproduce this issue

1. 我定义了一个返回类型 ResponseEntity
   public class ResponseEntity extends LinkedHashMap<String,Object> implements Serializable {...}
   @OverRide
   public ResponseEntity sayHello(String a) {
   return ResponseEntity.fromResult(0,a);
   }
   那么启动时会报错，org.apache.dubbo.metadata.definition.builder.MapTypeBuilder#build，if (actualTypeArgsLength != 2) {。。。}
   不明白为什么要写死
   2.如果我将ResponseEntity改为2目：
   public class ResponseEntity<T,Object> extends LinkedHashMap<String,Object> implements Serializable {...}
   @OverRide
   public ResponseEntity<String,Object> sayHello(String a) {
   return ResponseEntity.fromResult(0,a);
   }
   ...这样就可以，这算是一个bug么？ 我看21年的时候有人提出过，但新版本也没改善。

Expected Behavior

Actual Behavior

If there is an exception, please attach the exception trace:

Just put your stack trace here!

Caused by: java.lang.IllegalArgumentException: [ServiceDefinitionBuilder] Map type [com.freestyle.common.models.ResponseEntity<java.lang.String>] with unexpected amount of arguments [[Ljava.lang.reflect.Type;@3c1f2651].[class java.lang.String]
	at org.apache.dubbo.metadata.definition.builder.MapTypeBuilder.build(MapTypeBuilder.java:56)
	at org.apache.dubbo.metadata.definition.TypeDefinitionBuilder.build(TypeDefinitionBuilder.java:56)
	at org.apache.dubbo.metadata.definition.TypeDefinitionBuilder.build(TypeDefinitionBuilder.java:80)

[tiger822]

单目或3目的就有问题，如下

`
@DaTa
@NoArgsConstructor
@AllArgsConstructor
public class ResponseEntity extends LinkedHashMap<String,Object> implements Serializable {
private long id;
private int errCode;
private String message;
private T result;
public static ResponseEntity fromResult(long id, V val){
ResponseEntity ret = new ResponseEntity<>();
ret.result = val;
ret.id=id;
return ret;
}
public static ResponseEntity fromErr(long id, int errCode, String message){
ResponseEntity ret=new ResponseEntity(id,errCode,message,null);
return ret;
}
@JsonIgnore
public Map toMap(){
Map map= JsonUtils.fromJson(JsonUtils.toJsonString(this), HashMap.class);
return map;
}
}

`

[tiger822]

硬要改为2目的就没问题
`
@DaTa
@NoArgsConstructor
@AllArgsConstructor
public class ResponseEntity<V,T> extends LinkedHashMap<String,V> implements Serializable {
private long id;
private int errCode;
private String message;
private T result;
public static <V,T> ResponseEntity<V,T> fromResult(long id, T val){
ResponseEntity<V,T> ret = new ResponseEntity<>();
ret.result = val;
ret.id=id;
return ret;
}
public static <V,T>ResponseEntity<V,T> fromErr(long id, int errCode, String message){
ResponseEntity<V,T> ret=new ResponseEntity<>(id,errCode,message,(T)null);
return ret;
}
@JsonIgnore
public Map toMap(){
Map map= JsonUtils.fromJson(JsonUtils.toJsonString(this), HashMap.class);
return map;
}
}

`

[tiger822]

解决了， https://blog.csdn.net/rocklee/article/details/123796775

[wangchengming666]

翻了以前的一些issue 比如 #8212 和 #5122 都提到过这个问题，我认为这段强校验的代码没必要存在。

        if (actualTypeArgsLength != 2) {
            throw new IllegalArgumentException(MessageFormat.format(
                    "[ServiceDefinitionBuilder] Map type [{0}] with unexpected amount of arguments [{1}]."
                            + Arrays.toString(actualTypeArgs), type, actualTypeArgs));
        }

虽然可以通过SPI来扩展，但是还是给用户带来了一定的困扰。

[tiger822]

第一次遇见阿里产品里面响应这么快的，给你666个赞，thanks!