Custom ROS message triggers ClassNotFoundException even though it shows up in rosmsg list

4 次查看（过去 30 天）
Florian H
Florian H 2020-9-1
回答： Florian H 2020-9-1
I'm currently playing around with custom ROS message definitions in MATLAB R2020a.
I generated my custom messages following the tutorial. They successfully build without any problems and show up when using rosmsg list after restarting MATLAB.
However, when I now try to read the message from a topic in a ROS bag file, the class definitions can't be found, prompting the following error:
Error using ros.BagSelection/deserializeMessages (line 641)
Java exception occurred:
org.ros.exception.RosMessageRuntimeException: java.lang.ClassNotFoundException:
custom_msgs.ObjectList
at
org.ros.internal.message.definition.MessageDefinitionReflectionProvider.get(MessageDefinitionReflectionProvider.java:66)
at
org.ros.internal.message.DefaultMessageFactory.newFromType(DefaultMessageFactory.java:42)
at
org.ros.internal.message.DefaultMessageDeserializer.deserialize(DefaultMessageDeserializer.java:42)
Caused by: java.lang.ClassNotFoundException: custom_msgs.ObjectList
at java.net.URLClassLoader.findClass(URLClassLoader.java:382)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
at
org.ros.internal.message.definition.MessageDefinitionReflectionProvider.get(MessageDefinitionReflectionProvider.java:62)
... 2 more
Error in ros.BagSelection/deserializeMessages (line 641)
msg{i,1} = ros.msg.internal.MessageFactory.newFromJava(msgType,
des.deserialize(cbuffer));
Error in ros.BagSelection/readMessages (line 278)
msgs = obj.deserializeMessages(obj.MessageList, rows);
Error in TestClass/visualizeData (line 77)
data = readMessages(topic, i);
When trying to retrieve the message defintion with rosmsg show custom_msgs.ObjectList, the same problem occurs:
Could not find definition of message type custom_msgs/ObjectList. Check the spelling of
the type, or use "rosmsg list" to retrieve a list of available message types.
ObjectList.msg is defined as following:
std_msgs/Header header # Time stamp for the object list is in the header
ObjectData[] objects # List of objects

请先登录，再回答此问题。

采纳的回答

Florian H
Florian H 2020-9-1
Adding the path of your generated messages files to javaclasspath.txt (as indicated in the command window when generating the messages) fixed the problem.

更多回答（0 个）

类别

在 Help Center 和 File Exchange 中查找有关 ROS Network Connection and Exploration 的更多信息

标签

产品


版本

R2020a

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!

Translated by