聊聊rocketmq的RemotingCommandException

public class RemotingCommandException extends RemotingException {
    private static final long serialVersionUID = -6061365915274953096L;
​
    public RemotingCommandException(String message) {
        super(message, null);
    }
​
    public RemotingCommandException(String message, Throwable cause) {
        super(message, cause);
    }
}

public class RemotingCommand {
​
    //......
​
    public CommandCustomHeader decodeCommandCustomHeader(
        Class<? extends CommandCustomHeader> classHeader) throws RemotingCommandException {
        CommandCustomHeader objectHeader;
        try {
            objectHeader = classHeader.newInstance();
        } catch (InstantiationException e) {
            return null;
        } catch (IllegalAccessException e) {
            return null;
        }
​
        if (this.extFields != null) {
​
            Field[] fields = getClazzFields(classHeader);
            for (Field field : fields) {
                if (!Modifier.isStatic(field.getModifiers())) {
                    String fieldName = field.getName();
                    if (!fieldName.startsWith("this")) {
                        try {
                            String value = this.extFields.get(fieldName);
                            if (null == value) {
                                if (!isFieldNullable(field)) {
                                    throw new RemotingCommandException("the custom field <" + fieldName + "> is null");
                                }
                                continue;
                            }
​
                            field.setAccessible(true);
                            String type = getCanonicalName(field.getType());
                            Object valueParsed;
​
                            if (type.equals(STRING_CANONICAL_NAME)) {
                                valueParsed = value;
                            } else if (type.equals(INTEGER_CANONICAL_NAME_1) || type.equals(INTEGER_CANONICAL_NAME_2)) {
                                valueParsed = Integer.parseInt(value);
                            } else if (type.equals(LONG_CANONICAL_NAME_1) || type.equals(LONG_CANONICAL_NAME_2)) {
                                valueParsed = Long.parseLong(value);
                            } else if (type.equals(BOOLEAN_CANONICAL_NAME_1) || type.equals(BOOLEAN_CANONICAL_NAME_2)) {
                                valueParsed = Boolean.parseBoolean(value);
                            } else if (type.equals(DOUBLE_CANONICAL_NAME_1) || type.equals(DOUBLE_CANONICAL_NAME_2)) {
                                valueParsed = Double.parseDouble(value);
                            } else {
                                throw new RemotingCommandException("the custom field <" + fieldName + "> type is not supported");
                            }
​
                            field.set(objectHeader, valueParsed);
​
                        } catch (Throwable e) {
                            log.error("Failed field [{}] decoding", fieldName, e);
                        }
                    }
                }
            }
​
            objectHeader.checkFields();
        }
​
        return objectHeader;
    }
​
    private boolean isFieldNullable(Field field) {
        if (!NULLABLE_FIELD_CACHE.containsKey(field)) {
            Annotation annotation = field.getAnnotation(CFNotNull.class);
            synchronized (NULLABLE_FIELD_CACHE) {
                NULLABLE_FIELD_CACHE.put(field, annotation == null);
            }
        }
        return NULLABLE_FIELD_CACHE.get(field);
    }
​
    //......
}