feat: better unwrapping of java exception

README.md

@@ -320,6 +320,89 @@ service EchoService {
  }
 ```
 
+### 异常处理
+
+**codec-dubbo** 将异常定义为实现了以下接口的错误，你可以像处理错误一样处理 java 中的异常：
+```go
+type Throwabler interface {
+	Error() string
+	JavaClassName() string
+	GetStackTrace() []StackTraceElement
+}
+```
+
+#### 常见异常
+
+**codec-dubbo** 在[pkg/hessian2/exception](https://github.com/kitex-contrib/codec-dubbo/tree/main/pkg/hessian2/exception)目录下提供了java中常见的异常，目前支持 java.lang.Exception ，更多异常将在后续迭代中加入。
+常见异常无需命令行工具的支持，直接引用即可。
+
+##### client端提取异常
+
+```go
+import (
+	hessian2_exception "github.com/kitex-contrib/codec-dubbo/pkg/hessian2/exception"
+)
+
+func main() {
+	resp, err := cli.Greet(context.Background(), true)
+	if err != nil {
+		// FromError 返回 Throwabler
+        exceptionRaw, ok := hessian2_exception.FromError(err)
+        if !ok {
+        // 视作常规错误处理	
+        } else {
+            // 若不关心 exceptionRaw 的具体类型，直接调用 Throwabler 提供的方法即可
+            klog.Errorf("get %s type Exception", exceptionRaw.JavaClassName())
+
+            // 若想获得 exceptionRaw 的具体类型，需要进行类型转换，但前提是已知该具体类型
+            exception := exceptionRaw.(*hessian2_exception.Exception)
+        }
+    }
+}
+```
+
+##### server端返回异常
+
+```go
+import (
+	hessian2_exception "github.com/kitex-contrib/codec-dubbo/pkg/hessian2/exception"
+)
+
+func (s *GreetServiceImpl) Greet(ctx context.Context, req string) (resp string, err error) {
+    return "", hessian2_exception.NewException("Your detailed message")
+}
+```
+
+#### 自定义异常
+
+java 中的自定义业务异常往往会继承一个基础异常，这里以 CustomizedException 为例，CustomizedException 继承了 java.lang.Exception：
+```java
+public class CustomizedException extends Exception {
+    private final String customizedMessage;
+    public CustomizedException(String customizedMessage) {
+        super();
+        this.customizedMessage = customizedMessage;
+    }
+
+    public String getCustomizedMessage() {
+        return this.customizedMessage;
+    }
+}
+```
+
+为了在 kitex 侧定义与之对应的异常，在 **thrift** 中编写如下定义：
+
+```thrift
+exception CustomizedException {
+    1: required java.Exception exception (thrift.nested="true")
+    2: required string customizedMessage
+}(JavaClassName="org.cloudwego.kitex.samples.api.CustomizedException")
+```
+
+和[其它类型](#其它类型javalangobject-javautildate)一样，需要在使用 **kitex** 脚手架工具生成代码时添加 `-hessian2 java_extension` 参数来拉取拓展包。 
+
+使用方法与[常见异常](#常见异常)一致。
+
 ## 服务注册与发现
 
 > 目前仅支持基于 zookeeper 的**接口级**服务发现与服务注册，**应用级**服务发现以及服务注册计划在后续迭代中支持。

README_ENG.md

@@ -314,6 +314,90 @@ service EchoService {
  }
 ```
 
+### Exception Handling
+
+**codec-dubbo** defines exceptions as **error** that implement the following interface. You can handle exceptions in Java as you could handle **error** in Go:
+
+```go
+type Throwabler interface {
+	Error() string
+	JavaClassName() string
+	GetStackTrace() []StackTraceElement
+}
+```
+
+#### Common Exceptions
+
+**codec-dubbo** provides commonly used Java exceptions in the [pkg/hessian2/exception](https://github.com/kitex-contrib/codec-dubbo/tree/main/pkg/hessian2/exception) directory. Currently, it supports java.lang.Exception, and more exceptions will be added in subsequent iterations.
+Common exceptions do not require command line tool support and could be directly referenced.
+
+##### Extracting Exception on the Client Side
+
+```go
+import (
+	hessian2_exception "github.com/kitex-contrib/codec-dubbo/pkg/hessian2/exception"
+)
+
+func main() {
+	resp, err := cli.Greet(context.Background(), true)
+	if err != nil {
+        // FromError returns a Throwabler
+        exceptionRaw, ok := hessian2_exception.FromError(err)
+        if !ok {
+        // Treat as a regular error handling	
+        } else {
+            // If you are not concerned with the specific type of exceptionRaw, just call the methods provided by Throwabler
+            klog.Errorf("get %s type Exception", exceptionRaw.JavaClassName())
+
+            // If you want to obtain the specific type of exceptionRaw, you need to perform a type conversion, but this requires knowing the specific type
+            exception := exceptionRaw.(*hessian2_exception.Exception)
+        }
+    }
+}
+```
+
+##### Returning Exception on the Server Side
+
+```go
+import (
+	hessian2_exception "github.com/kitex-contrib/codec-dubbo/pkg/hessian2/exception"
+)
+
+func (s *GreetServiceImpl) Greet(ctx context.Context, req string) (resp string, err error) {
+    return "", hessian2_exception.NewException("Your detailed message")
+}
+```
+
+#### Customized Exceptions
+
+Customized business exceptions in Java often inherit a base exception. Here, we use CustomizedException as an example, which inherits from java.lang.Exception:
+
+```java
+public class CustomizedException extends Exception {
+    private final String customizedMessage;
+    public CustomizedException(String customizedMessage) {
+        super();
+        this.customizedMessage = customizedMessage;
+    }
+
+    public String getCustomizedMessage() {
+        return this.customizedMessage;
+    }
+}
+```
+
+To define a corresponding exception on the kitex side, write the following definition in **thrift**:
+
+```thrift
+exception CustomizedException {
+    1: required java.Exception exception (thrift.nested="true")
+    2: required string customizedMessage
+}(JavaClassName="org.cloudwego.kitex.samples.api.CustomizedException")
+```
+
+Like [other types](#other-types--javalangobject-javautildate-), you need to add the `-hessian2 java_extension` parameter when generating code with the **kitex** scaffolding tool to pull the extension package.
+
+The usage is consistent with [Common Exceptions](#common-exceptions).
 
 ## Service Registry and Service Discovery
 

java/java-reflection.go

@@ -29,24 +29,26 @@ import (
 // IDL Path: java.thrift
 
 var file_java_thrift_go_types = []interface{}{
-	(*Object)(nil), // Struct 0: java.Object
-	(*Date)(nil),   // Struct 1: java.Date
+	(*Object)(nil),    // Struct 0: java.Object
+	(*Date)(nil),      // Struct 1: java.Date
+	(*Exception)(nil), // Struct 2: java.Exception
 }
 
 var (
 	file_java_thrift      *thrift_reflection.FileDescriptor
 	file_idl_java_rawDesc = []byte{
-		0x1f, 0x8b, 0x8, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xff, 0x8c, 0x8f, 0x4d, 0xe, 0x82, 0x30,
-		0x10, 0x85, 0x9f, 0xa5, 0xe0, 0xcf, 0x50, 0xeb, 0x49, 0x7a, 0x9, 0x5d, 0xb9, 0xd0, 0x33, 0x8c,
-		0xa6, 0x22, 0xa4, 0x6a, 0x22, 0x95, 0xf3, 0x9b, 0x29, 0x65, 0x65, 0x4c, 0x58, 0x7d, 0x4d, 0xfa,
-		0xde, 0xf7, 0x32, 0x84, 0x5, 0x0, 0xea, 0x78, 0x60, 0x17, 0xef, 0xef, 0xf6, 0x16, 0xd, 0x14,
-		0x11, 0x0, 0x18, 0x14, 0xe9, 0x21, 0x1, 0xd5, 0xbc, 0x0, 0x68, 0x89, 0x59, 0xe8, 0x5a, 0xbe,
-		0x2d, 0x4a, 0xa1, 0xfa, 0x35, 0x10, 0x14, 0x80, 0xea, 0x7c, 0xe9, 0xfc, 0x35, 0x5a, 0x14, 0xf5,
-		0x68, 0xd3, 0x64, 0xb3, 0xcd, 0x1c, 0x79, 0xe0, 0x7d, 0xe0, 0xbe, 0x3f, 0xf1, 0xc3, 0x4f, 0x1b,
-		0xbb, 0xa4, 0x8, 0xfc, 0x6c, 0xdc, 0x58, 0x25, 0x94, 0xd2, 0xc4, 0xbf, 0x5, 0x7d, 0xe0, 0xe8,
-		0xe7, 0xfb, 0xb7, 0x49, 0xf0, 0x89, 0x6d, 0x70, 0x52, 0x9c, 0xec, 0x16, 0x55, 0xbe, 0x67, 0x99,
-		0xb9, 0xca, 0x5c, 0x67, 0x6e, 0x12, 0xf1, 0xd, 0x0, 0x0, 0xff, 0xff, 0xaf, 0x1, 0x47, 0x6a,
-		0x2b, 0x1, 0x0, 0x0,
+		0x1f, 0x8b, 0x8, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0xff, 0x8c, 0x90, 0x41, 0xae, 0x82, 0x30,
+		0x18, 0x84, 0xe7, 0x41, 0xe1, 0x89, 0x3f, 0x58, 0x13, 0xef, 0xc1, 0x25, 0xd4, 0x8d, 0xb, 0x3d,
+		0xc3, 0x2f, 0xa9, 0x8, 0xa9, 0x60, 0xa4, 0x12, 0x8f, 0x6f, 0x5a, 0x8a, 0x2e, 0x8c, 0x91, 0xd5,
+		0xd7, 0xa4, 0x33, 0xdf, 0xa4, 0x25, 0xfc, 0x1, 0xa0, 0x9a, 0x7b, 0xce, 0xcd, 0xf9, 0x56, 0x9d,
+		0x4c, 0x86, 0x80, 0x8, 0x0, 0x32, 0x84, 0xee, 0x60, 0x3, 0x41, 0xd9, 0x2, 0x10, 0x36, 0x26,
+		0x21, 0x52, 0x7b, 0x2d, 0x11, 0x59, 0x86, 0x9f, 0x6, 0x42, 0x0, 0x20, 0x3e, 0x1c, 0x6b, 0x55,
+		0x18, 0x89, 0x30, 0x1d, 0x6c, 0x82, 0xa4, 0xb7, 0x65, 0x3b, 0xee, 0x79, 0xad, 0xb9, 0xeb, 0xf6,
+		0x7c, 0x51, 0xe3, 0xc6, 0xd2, 0x29, 0x34, 0x37, 0x65, 0x3e, 0x54, 0x9, 0x91, 0x6d, 0xe2, 0xdb,
+		0x82, 0xd8, 0xb0, 0x51, 0xd3, 0xfd, 0xb, 0x27, 0xb8, 0x9b, 0x4a, 0xe7, 0xb6, 0xf8, 0xcb, 0x9e,
+		0x6c, 0x1f, 0x85, 0xba, 0x9a, 0xaa, 0x6d, 0xa6, 0x4f, 0xac, 0xde, 0x4f, 0x78, 0xb5, 0xc7, 0x1d,
+		0x89, 0xd8, 0xff, 0xdb, 0xbf, 0xe7, 0xcc, 0x33, 0xf1, 0x9c, 0x3b, 0xe2, 0x19, 0x0, 0x0, 0xff,
+		0xff, 0xf9, 0xde, 0xba, 0xfa, 0x93, 0x1, 0x0, 0x0,
 	}
 )
 

java/java.go

@@ -21,6 +21,8 @@ package java
 
 import (
 	"time"
+
+	hessian2_exception "github.com/kitex-contrib/codec-dubbo/pkg/hessian2/exception"
 )
 
 type Object = interface{}
@@ -34,3 +36,9 @@ type Date = time.Time
 func NewDate() *Date {
 	return new(Date)
 }
+
+type Exception = hessian2_exception.Exception
+
+func NewException(detailMessage string) *Exception {
+	return hessian2_exception.NewException(detailMessage)
+}

java/java.thrift

@@ -3,3 +3,5 @@ namespace go java
 struct Object {} (JavaClassName="java.lang.Object")
 
 struct Date {} (JavaClassName="java.util.Date")
+
+struct Exception {} (JavaClassName="java.lang.Exception")

pkg/codec.go

@@ -23,6 +23,8 @@ import (
 	"context"
 	"fmt"
 
+	hessian2_exception "github.com/kitex-contrib/codec-dubbo/pkg/hessian2/exception"
+
 	"github.com/kitex-contrib/codec-dubbo/registries"
 
 	"github.com/cloudwego/kitex/pkg/remote"
@@ -182,12 +184,13 @@ func (m *DubboCodec) encodeExceptionPayload(ctx context.Context, message remote.
 	if !ok {
 		return nil, fmt.Errorf("%v exception does not implement Error", data)
 	}
-	if exception, ok := data.(hessian2.Throwabler); ok {
+	// exception is wrapped by kerrors.DetailedError
+	if exception, ok := hessian2_exception.FromError(errRaw); ok {
 		if err := encoder.Encode(exception); err != nil {
 			return nil, err
 		}
 	} else {
-		if err := encoder.Encode(hessian2.NewException(errRaw.Error())); err != nil {
+		if err := encoder.Encode(hessian2_exception.NewException(errRaw.Error())); err != nil {
 			return nil, err
 		}
 	}

pkg/hessian2/exception/exception.go

@@ -0,0 +1,59 @@
+/*
+ * Copyright 2023 CloudWeGo Authors
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package exception
+
+import (
+	"github.com/apache/dubbo-go-hessian2/java_exception"
+)
+
+type Throwabler = java_exception.Throwabler
+
+type Exception = java_exception.Exception
+
+func NewException(detailMessage string) *Exception {
+	return java_exception.NewException(detailMessage)
+}
+
+// FromError extracts Throwabler from passed err.
+//
+//   - If err is nil, it returns nil and false
+//
+//   - If err implements Unwrap(), it would unwrap err until getting the real cause.
+//     Then it would check cause whether implementing Throwabler. If yes, it returns
+//     Throwabler and true.
+//
+//     If not, it checks err whether implementing Throwabler directly. If yes,
+//     it returns Throwabler and true.
+func FromError(err error) (Throwabler, bool) {
+	if err == nil {
+		return nil, false
+	}
+	for {
+		if wrapper, ok := err.(interface{ Unwrap() error }); ok {
+			err = wrapper.Unwrap()
+		} else {
+			break
+		}
+	}
+	if exception, ok := err.(Throwabler); ok {
+		return exception, true
+	}
+	return nil, false
+}