The getLibPath method returns the path to a directory containing the jar files constituting the classpath for the module the class is a part of. I was using the Maven dependency: org.
I am also keeping a map of class loaders so that they can be reused if the class I am trying to instantiate is in the same module as a class that I have already instantiated, which I would recommend. I know I'm late to the party, but I have been using pf4j , which is a plug-in framework, and it works pretty well. For further details please refer to the documentation. This lib will load jar from file system or any other location. It will dedicate a class loader for the jar to make sure there are no library conflicts.
Users will be able to create any object from the loaded jar and call any method on it. This lib was designed to load jars compiled in Java 8 from the code base that supports Java 7. ObjectBuilder supports factory methods, calling static functions, and call back interface implementations. This can be a late response, I can do it as this a simple example for fastutil Here is the method to do it using Spring Boot 1.
This modification has no problem with changing the jar file during application operation, like the standard URLClassloader. All loaded jar files are loaded into RAM and thus independent of the original file. In-memory jar and JDBC class loader. I personally find that java. ServiceLoader does the job pretty well. You can get an example here.
Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. How to load JAR files dynamically at Runtime? Ask Question. Asked 13 years, 2 months ago. Active 6 months ago. Viewed k times. Any suggestions for simple code that does this? Improve this question.
JohanC Allain Lalonde Allain Lalonde I want to do the same but run the loaded jar in a more sandboxed environment for security reasons obviously. For example, I want to block all network and filesystem access.
TylerMarshall Allain Lalonde below showed how and it isn't hard, also on other systems it is rather simple.
I didn't need to duplicate the answers it's a bad attitude to do that, one good is enough, but I wanted to highlight to the OP that what he qualifies as "hard" is not and his statement is false. Add a comment. Active Oldest Votes. Improve this answer. Konrad Rudolph k gold badges silver badges bronze badges. Only problem with this approach is that you need to know what classes are in what jars. As opposed to just loading a directory of jars and then instantiating classes. I am misunderstanding it?
Using this approach you need to make sure you won't call this load method more than once for each class.
Since you're creating a new class loader for every load operation, it can not know whether the class was already loaded previously. This can have bad consequences. For example singletons not working because the class was loaded several times and so the static fields exist several times. Even with dependencies to other classes inside the jar.
The first line was incomplete. Show 4 more comments. Karl Richter 6, 18 18 gold badges 62 62 silver badges bronze badges. All the activity on this response makes me wonder how much hacks we are running in production in different systems. I'm not sure I want to know the answer — Andrei Savu. FiReTiTi Yes!! Show 6 more comments. Martin Klinke Martin Klinke 7, 5 5 gold badges 39 39 silver badges 62 62 bronze badges. MyClass" ;. Chris Chris It's also buggy and missing some important implementations i.
I'm still wondering SergeyKarpushin's claims are still present since the project has been updated over time to second major version. Would like to hear experience. I still work on java projects, and I don't have any evidences that Open JDK will fail you these days I had issue back then though.
Skip to main content. Java Enterprise in a Nutshell, Second Edition by. Start your free trial. When a Java program uses a ClassLoader , that class loader needs to know the location s from which it should be allowed to load classes. Usually, a class loader is used in conjunction with an HTTP server that is serving up compiled classes for the Java platform.
For example, the HTML source will contain something like:. A codebase can be defined as a source, or a place, from which to load classes into a virtual machine. For example, if you invited a new friend over for dinner, you would need to give that friend directions to the place where you lived, so that he or she could locate your house. Similarly, you can think of a codebase as the directions that you give to a VM, so it can find your [potentially remote] classes.
To interact with an applet, that applet and any classes that it needs to run must be accessible by remote clients. In order for a client to call methods on a remote object, the client must have a way to communicate with the remote object. Rather than having to program the client to speak the remote object's protocol, Java RMI uses special classes called stubs that can be downloaded to the client that are used to communicate with make method calls on the remote object.
The java. Generally, the classes needed to execute remote method calls should be made accessible from a network resource, such as an HTTP or FTP server. In addition to downloading stubs and their associated classes to clients, the java. When a client makes a method call to a remote object, the method that it calls could be written to accept no arguments or a number of arguments. There are three distinct cases that may occur, based on the data type s of the method argument s.
In the first case, all of the method parameters and return value are primitive data types, so the remote object knows how to interpret them as method parameters, and there is no need to check its CLASSPATH or any codebase. In the second case, at least one remote method parameter or the return value is an object, for which the remote object can find the class definition locally in its CLASSPATH.
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