在运行时从 spring 引导中的外部文件夹加载 jar 文件

Question

I have a spring boot application. I want to load external jars from an external folder at runtime in the spring boot application context without restarting the context.

I checked the below answer which uses class loader to load the classes at runtime. The solution is very old.

How to load Classes at runtime from a folder or JAR?

Just wanted to know if there is any other way to load jars at runtime.

Answer 1

Somehow I was able to load the @Component classes in the spring context at runtime.Can someone please let me know if there is any other easier way i can achieve the same:

@Component
public class CustomClassLoader {

 @Autowired
 ConfigurableApplicationContext applicationContext;

 
  public void loadJar() throws ClassNotFoundException {

    JarClassLoader jcl = new JarClassLoader();

    jcl.add("D:\\new\\test");  //loaded all the jars from test folder

    Map<String, byte[]> loadedResourceMap = jcl.getLoadedResources();

    Set<String> loadedSet= loadedResourceMap.keySet().stream()
        .filter(s -> s.startsWith("com/test/package/ext/")).collect(Collectors.toSet()); 

    for (String localSet : loadedSet) {
      String modifiedString = localSet.replace("/", ".").replace(".class", "");
      logger.info("modified string " + modifiedString);

      final Class<?> loadedClass = jcl.loadClass(modifiedString);

      try {
        Object loadedObject =  applicationContext.getAutowireCapableBeanFactory()
            .createBean(loadedClass); //autowiring the loaded classes
             } catch (Exception e) {
        logger.info("Exception occured while loading " + modifiedString
            + " exception is" + e.getStackTrace());
      }
    }

  }

}

Answer 2

You might want to delay loading these components which are depend on the external jars. Please check if you can use @Lazy. Below link can be helpful https://www.logicbig.com/tutorials/spring-framework/spring-core/lazy-at-injection-point.html