Develop Reference

Jetty ServletContextHandler setClassLoader not working on every request thread

I tried to develop multiple webservices using RESTEasy and Jetty. Im planning to make each of the webservice to have its own set of JAR files which will be loaded from certain directory.
What I have done is I create custom ClassLoader like this
public class AppClassLoader extends ClassLoader{
static Logger log = Logger.getLogger(AppClassLoader.class.getName());
String libPath = "";
public AppClassLoader(String libPath) {
this.libPath = libPath;
}
#Override
public Class loadClass(String name) throws ClassNotFoundException {
Class clazz = findLoadedClass(name);
if(clazz == null) {
try {
clazz = ClassLoader.getSystemClassLoader().loadClass(name);
if(clazz == null) {
clazz = getClass(name);
if(clazz == null) {
throw new ClassNotFoundException();
}
}
return clazz;
}catch (ClassNotFoundException e) {
// TODO: handle exception
throw new ClassNotFoundException();
}
}else {
return getSystemClassLoader().loadClass(name);
}
}
private Class<?> getClass(String name) throws ClassNotFoundException {
try {
File dir = new File(this.libPath);
if(dir.isDirectory()) {
for(File jar : dir.listFiles()) {
JarFile jarFile = new JarFile(jar.getPath());
Enumeration<JarEntry> e = jarFile.entries();
URL[] urls = { new URL("jar:file:" + jar.getPath()+"!/") };
URLClassLoader cl = URLClassLoader.newInstance(urls);
while (e.hasMoreElements()) {
JarEntry je = e.nextElement();
if(je.isDirectory() || !je.getName().endsWith(".class")){
continue;
}
String className = je.getName().substring(0,je.getName().length()-6);
className = className.replace('/', '.');
if(className.equals(name)) {
return cl.loadClass(className);
}
}
}
}
} catch (IOException e) {
e.printStackTrace();
return null;
}
return null;
}
And then what I did is assign this custom class loader into ServletContextHandler when I initialized Jetty and RestEasy to start the server, like below
final int port = 8080;
final Server server = new Server(port);
// Setup the basic Application "context" at "/".
// This is also known as the handler tree (in Jetty speak).
final ServletContextHandler context = new ServletContextHandler(server, CONTEXT_ROOT);
AppClassLoader classLoader = new AppClassLoader("../apps/dummy/lib");
context.setClassLoader(classLoader);
// Setup RESTEasy's HttpServletDispatcher at "/api/*".
final ServletHolder restEasyServlet = new ServletHolder(new HttpServletDispatcher());
restEasyServlet.setInitParameter("resteasy.servlet.mapping.prefix",APPLICATION_PATH);
restEasyServlet.setInitParameter("javax.ws.rs.Application",App.class.getCanonicalName());
final ServletHolder servlet = new ServletHolder(new HttpServletDispatcher());
context.addServlet(restEasyServlet, APPLICATION_PATH + "/*");
server.start();
server.join();
And then in the jax-rs endpoint I have this code
#Path("/")
public class Dummy {
Logger log = Logger.getLogger(Dummy.class.getName());
#GET
#Path("dummy")
#Produces(MediaType.TEXT_PLAIN)
public String test() {
HikariConfig src = new HikariConfig();
JwtMap jw = new JwtMap();
return "This is DUMMY service : "+src.getClass().getName().toString()+" ### "+jw.getClass().getName();
}}
I managed to start the server just fine, but when I tried to call the webservice, it return
java.lang.NoClassDefFoundError: com/zaxxer/hikari/HikariConfig
And then I see the classLoader used in the thread is not my custom class loader but the java standard class loader.
Which part that I did wrong here? Im so new to this classs loading stuff and I am not sure I literally understand how to used it.
Regards

By Default, ClassLoaders works on Parent first strategy. That means that Classes are searched and loaded through the sequence
Bootstrap Class Loader -> Ext Class Loader -> System Class Loader ->
Custom Class Loader
So, with that approach Dummy Class is loaded using System Class Loader. Now, classes loaded through a ClassLoader only has the visibility to the classes from Parent ClassLoader and not vice versa. So, HikariConfig class is not visible to the Dummy Class. Hence, the exception.
But, you should be able to load a class this way using the ServletContext Classloader which in your case is the Custom ClassLoader.
Inject the Servlet Context in your Dummy class and then
servletContext.getClassLoader().loadClass("com.zaxxer.hikari.HikariConfig");

How to serve static content and resource at same base url with Grizzly

I am using Grizzly to serve my REST service which can have multiple "modules". I'd like to be able to use the same base URL for the service and for static content so I can access all these urls:
http://host:port/index.html
http://host:port/module1/index.html
http://host:port/module1/resource
http://host:port/module2/index.html
http://host:port/module2/resource
The code I'm trying to set this up with looks like this:
private HttpServer createServer(String host, int port, ResourceConfig config)
{
HttpServer server = GrizzlyHttpServerFactory.createHttpServer(URI.create("http://" + host + ":" + port + "/"), config, false);
HttpHandler httpHandler = new CLStaticHttpHandler(HttpServer.class.getClassLoader(), "docs/");
server.getServerConfiguration().addHttpHandler(httpHandler, "/");
return server;
}
With this code, I am only able to see the html pages and I get a "Resource identified by path does not exist" response when I try to get my resources.
When I comment out the code to add the HttpHandler, then I am able to access my resources (but don't have the docs of course).
What do I need to do to access both my resources and my static content?

I ended up writing a service to handle static resources myself. I decided to serve my files from the file system, but this approach would also work for serving them from a jar - you'd just have to get the file as a resource instead of creating the File directly.
#Path("/")
public class StaticService
{
#GET
#Path("/{docPath:.*}.{ext}")
public Response getHtml(#PathParam("docPath") String docPath, #PathParam("ext") String ext, #HeaderParam("accept") String accept)
{
File file = new File(cleanDocPath(docPath) + "." + ext);
return Response.ok(file).build();
}
#GET
#Path("{docPath:.*}")
public Response getFolder(#PathParam("docPath") String docPath)
{
File file = null;
if ("".equals(docPath) || "/".equals(docPath))
{
file = new File("index.html");
}
else
{
file = new File(cleanDocPath(docPath) + "/index.html");
}
return Response.ok(file).build();
}
private String cleanDocPath(String docPath)
{
if (docPath.startsWith("/"))
{
return docPath.substring(1);
}
else
{
return docPath;
}
}
}

One thing you can do is run Grizzly as a servlet container. That way you can run Jersey as servlet filter, and add a default servlet to handle the static content. For example
public class Main {
public static HttpServer createServer() {
WebappContext context = new WebappContext("GrizzlyContext", "");
createJerseyFilter(context);
createDefaultServlet(context);
HttpServer server = GrizzlyHttpServerFactory
.createHttpServer(URI.create("http://localhost:8080/"));
context.deploy(server);
return server;
}
private static void createJerseyFilter(WebappContext context) {
ResourceConfig rc = new ResourceConfig().packages("com.grizzly.test");
// This causes Jersey to forward 404s to default servlet
// which will catch all the static content requests.
rc.property(ServletProperties.FILTER_FORWARD_ON_404, true);
FilterRegistration reg = context.addFilter("JerseyApp", new ServletContainer(rc));
reg.addMappingForUrlPatterns(EnumSet.allOf(DispatcherType.class), "/*");
}
private static void createDefaultServlet(WebappContext context) {
ArraySet<File> baseDir = new ArraySet<>(File.class);
baseDir.add(new File("."));
ServletRegistration defaultServletReg
= context.addServlet("DefaultServlet", new DefaultServlet(baseDir) {});
defaultServletReg.addMapping("/*");
}
public static void main(String[] args) throws IOException {
HttpServer server = createServer();
System.in.read();
server.stop();
}
}
You will need to add the Jersey Grizzly servlet dependency
<dependency>
<groupId>org.glassfish.jersey.containers</groupId>
<artifactId>jersey-container-grizzly2-servlet</artifactId>
<version>${jersey2.version}</version>
</dependency>
The only problem with this approach is that the default servlet is meant to serve files from the file system, not from the classpath, as you are currently trying to do. You can see in the createDefaultServlet method I just set the base directory to the current working directory. So that's where all your files would need to be. You can change it to "docs" so all your files would be in the docs folder, which would be in the current working directory.
If you want to read files from the classpath, you may need to implement your own servlet. You can look at the source code for DefaultServlet and try to modify it to serve from the classpath. You can also check out Dropwizard's AssetServlet, which already does serve content from the classpath.
Or you can just say forget it, and just serve from the file system :-)

Programmatic SchemaExport / SchemaUpdate with Hibernate 5 and Spring 4

With Spring 4 and Hibernate 4, I was able to use Reflection to get the Hibernate Configuration object from the current environment, using this code:
#Autowired LocalContainerEntityManagerFactoryBean lcemfb;
EntityManagerFactoryImpl emf = (EntityManagerFactoryImpl) lcemfb.getNativeEntityManagerFactory();
SessionFactoryImpl sf = emf.getSessionFactory();
SessionFactoryServiceRegistryImpl serviceRegistry = (SessionFactoryServiceRegistryImpl) sf.getServiceRegistry();
Configuration cfg = null;
try {
Field field = SessionFactoryServiceRegistryImpl.class.getDeclaredField("configuration");
field.setAccessible(true);
cfg = (Configuration) field.get(serviceRegistry);
} catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException e) {
e.printStackTrace();
}
SchemaUpdate update = new SchemaUpdate(serviceRegistry, cfg);
With Hibernate 5, I must use some MetadataImplementor, which doesn't seems to be available from any of those objects. I also tried to use MetadataSources with the serviceRegistry. But it did say that it's the wrong kind of ServiceRegistry.
Is there any other way to get this working?

Basic idea for this problem is:
implementation of org.hibernate.integrator.spi.Integrator which stores required data to some holder. Register implementation as a service and use it where you need.
Work example you can find here https://github.com/valery-barysok/spring4-hibernate5-stackoverflow-34612019
create org.hibernate.integrator.api.integrator.Integrator class
import hello.HibernateInfoHolder;
import org.hibernate.boot.Metadata;
import org.hibernate.engine.spi.SessionFactoryImplementor;
import org.hibernate.service.spi.SessionFactoryServiceRegistry;
public class Integrator implements org.hibernate.integrator.spi.Integrator {
#Override
public void integrate(Metadata metadata, SessionFactoryImplementor sessionFactory, SessionFactoryServiceRegistry serviceRegistry) {
HibernateInfoHolder.setMetadata(metadata);
HibernateInfoHolder.setSessionFactory(sessionFactory);
HibernateInfoHolder.setServiceRegistry(serviceRegistry);
}
#Override
public void disintegrate(SessionFactoryImplementor sessionFactory, SessionFactoryServiceRegistry serviceRegistry) {
}
}
create META-INF/services/org.hibernate.integrator.spi.Integrator file
org.hibernate.integrator.api.integrator.Integrator
import org.hibernate.boot.spi.MetadataImplementor;
import org.hibernate.tool.hbm2ddl.SchemaExport;
import org.hibernate.tool.hbm2ddl.SchemaUpdate;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
#SpringBootApplication
public class Application implements CommandLineRunner {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
#Override
public void run(String... args) throws Exception {
new SchemaExport((MetadataImplementor) HibernateInfoHolder.getMetadata()).create(true, true);
new SchemaUpdate(HibernateInfoHolder.getServiceRegistry(), (MetadataImplementor) HibernateInfoHolder.getMetadata()).execute(true, true);
}
}

I would like to add up on Aviad's answer to make it complete as per OP's request.
The internals:
In order to get an instance of MetadataImplementor, the workaround is to register an instance of SessionFactoryBuilderFactory through Java's ServiceLoader facility. This registered service's getSessionFactoryBuilder method is then invoked by MetadataImplementor with an instance of itself, when hibernate is bootstrapped. The code references are below:
Service Loading
Invocation of getSessionFactoryBuilder
So, ultimately to get an instance of MetadataImplementor, you have to implement SessionFactoryBuilderFactory and register so ServiceLoader can recognize this service:
An implementation of SessionFactoryBuilderFactory:
public class MetadataProvider implements SessionFactoryBuilderFactory {
private static MetadataImplementor metadata;
#Override
public SessionFactoryBuilder getSessionFactoryBuilder(MetadataImplementor metadata, SessionFactoryBuilderImplementor defaultBuilder) {
this.metadata = metadata;
return defaultBuilder; //Just return the one provided in the argument itself. All we care about is the metadata :)
}
public static MetadataImplementor getMetadata() {
return metadata;
}
}
In order to register the above, create simple text file in the following path(assuming it's a maven project, ultimately we need the 'META-INF' folder to be available in the classpath):
src/main/resources/META-INF/services/org.hibernate.boot.spi.SessionFactoryBuilderFactory
And the content of the text file should be a single line(can even be multiple lines if you need to register multiple instances) stating the fully qualified class path of your implementation of SessionFactoryBuilderFactory. For example, for the above class, if your package name is 'com.yourcompany.prj', the following should be the content of the file.
com.yourcompany.prj.MetadataProvider
And that's it, if you run your application, spring app or standalone hibernate, you will have an instance of MetadataImplementor available through a static method once hibernate is bootstraped.
Update 1:
There is no way it can be injected via Spring. I digged into Hibernate's source code and the metadata object is not stored anywhere in SessionFactory(which is what we get from Spring). So, it's not possible to inject it. But there are two options if you want it in Spring's way:
Extend existing classes and customize all the way from
LocalSessionFactoryBean -> MetadataSources -> MetadataBuilder
LocalSessionFactoryBean is what you configure in Spring and it has an object of MetadataSources. MetadataSources creates MetadataBuilder which in turn creates MetadataImplementor. All the above operations don't store anything, they just create object on the fly and return. If you want to have an instance of MetaData, you should extend and modify the above classes so that they store a local copy of respective objects before they return. That way you can have a reference to MetadataImplementor. But I wouldn't really recommend this unless it's really needed, because the APIs might change over time.
On the other hand, if you don't mind building a MetaDataImplemetor from SessionFactory, the following code will help you:
EntityManagerFactoryImpl emf=(EntityManagerFactoryImpl)lcemfb.getNativeEntityManagerFactory();
SessionFactoryImpl sf=emf.getSessionFactory();
StandardServiceRegistry serviceRegistry = sf.getSessionFactoryOptions().getServiceRegistry();
MetadataSources metadataSources = new MetadataSources(new BootstrapServiceRegistryBuilder().build());
Metadata metadata = metadataSources.buildMetadata(serviceRegistry);
SchemaUpdate update=new SchemaUpdate(serviceRegistry,metadata); //To create SchemaUpdate
// You can either create SchemaExport from the above details, or you can get the existing one as follows:
try {
Field field = SessionFactoryImpl.class.getDeclaredField("schemaExport");
field.setAccessible(true);
SchemaExport schemaExport = (SchemaExport) field.get(serviceRegistry);
} catch (NoSuchFieldException | SecurityException | IllegalArgumentException | IllegalAccessException e) {
e.printStackTrace();
}

Take a look on this one:
public class EntityMetaData implements SessionFactoryBuilderFactory {
private static final ThreadLocal<MetadataImplementor> meta = new ThreadLocal<>();
#Override
public SessionFactoryBuilder getSessionFactoryBuilder(MetadataImplementor metadata, SessionFactoryBuilderImplementor defaultBuilder) {
meta.set(metadata);
return defaultBuilder;
}
public static MetadataImplementor getMeta() {
return meta.get();
}
}
Take a look on This Thread which seems to answer your needs

Well, my go to on this:
public class SchemaTranslator {
public static void main(String[] args) throws Exception {
new SchemaTranslator().run();
}
private void run() throws Exception {
String packageName[] = { "model"};
generate(packageName);
}
private List<Class<?>> getClasses(String packageName) throws Exception {
File directory = null;
try {
ClassLoader cld = getClassLoader();
URL resource = getResource(packageName, cld);
directory = new File(resource.getFile());
} catch (NullPointerException ex) {
throw new ClassNotFoundException(packageName + " (" + directory + ") does not appear to be a valid package");
}
return collectClasses(packageName, directory);
}
private ClassLoader getClassLoader() throws ClassNotFoundException {
ClassLoader cld = Thread.currentThread().getContextClassLoader();
if (cld == null) {
throw new ClassNotFoundException("Can't get class loader.");
}
return cld;
}
private URL getResource(String packageName, ClassLoader cld) throws ClassNotFoundException {
String path = packageName.replace('.', '/');
URL resource = cld.getResource(path);
if (resource == null) {
throw new ClassNotFoundException("No resource for " + path);
}
return resource;
}
private List<Class<?>> collectClasses(String packageName, File directory) throws ClassNotFoundException {
List<Class<?>> classes = new ArrayList<>();
if (directory.exists()) {
String[] files = directory.list();
for (String file : files) {
if (file.endsWith(".class")) {
// removes the .class extension
classes.add(Class.forName(packageName + '.' + file.substring(0, file.length() - 6)));
}
}
} else {
throw new ClassNotFoundException(packageName + " is not a valid package");
}
return classes;
}
private void generate(String[] packagesName) throws Exception {
Map<String, String> settings = new HashMap<String, String>();
settings.put("hibernate.hbm2ddl.auto", "drop-create");
settings.put("hibernate.dialect", "org.hibernate.dialect.PostgreSQL94Dialect");
MetadataSources metadata = new MetadataSources(
new StandardServiceRegistryBuilder()
.applySettings(settings)
.build());
for (String packageName : packagesName) {
System.out.println("packageName: " + packageName);
for (Class<?> clazz : getClasses(packageName)) {
System.out.println("Class: " + clazz);
metadata.addAnnotatedClass(clazz);
}
}
SchemaExport export = new SchemaExport(
(MetadataImplementor) metadata.buildMetadata()
);
export.setDelimiter(";");
export.setOutputFile("db-schema.sql");
export.setFormat(true);
export.execute(true, false, false, false);
}
}

Tomcat 8 new Resource implementation to map Jar files in a separate directory

With tomcat 8 I have extend the WebAppClassLoader and add some jar filed from a shared location to the classloader path using addRepository() method. With tomcat 8 addRepository have been removed and new resource implementation have been introduced. I'm still able to use the addUrl method to add jar files. But I would like to implement the new resource based implementation.
I've tried with
DirResourceSet dirResourceSet = new DirResourceSet(getContext().getResources(), "/WEB-INF/lib", "/home/thusitha/lib/runtimes/cxf", "/");
WebResourceRoot webResourceRoot = getContext().getResources();
webResourceRoot.getContext().getResources().addPreResources(dirResourceSet);
But this is not working and still it throws classnotfoundexception
Can someone tell me how to map a directory which contains jars to a particular webapp using Tomcat new resource implementation?

A solution to this problem is to register your resources by overriding the ContextConfig class (org.apache.catalina.startup.ContextConfig). Catalina enters a starting state immediately after it scans your document path for resources. Most of the processing of those resources, such as annotations, is handled by the ContextConfig LifecycleListener. To ensure the resources are added before the context configuration takes place, override the ContextConfig.
final Context currentContext = ctx;
ContextConfig ctxCfg = new ContextConfig() {
#Override
public void lifecycleEvent(LifecycleEvent event) {
if (event.getType().equals(Lifecycle.CONFIGURE_START_EVENT)) {
WebResourceRoot webResourcesRoot = currentContext.getResources();
String baseDir = Platform.getBaseDir(); // Server Base Directory
File libDir = new File(baseDir + File.separator + "lib");
DirResourceSet dirResourceSet = null;
try {
dirResourceSet = new DirResourceSet(webResourcesRoot, "/WEB-INF/lib", libDir.getCanonicalPath(), "/");
} catch (IOException e) {
throw new RuntimeException(e);
}
webResourcesRoot.addPostResources(dirResourceSet);
String[] possibleJars = dirResourceSet.list("/WEB-INF/lib");
for(String libfile : possibleJars) {
WebResource possibleJar = dirResourceSet.getResource("/WEB-INF/lib/"+libfile);
System.err.println(String.format("Loading possible jar %s",possibleJar.getCanonicalPath())); // Just checking...
if (possibleJar.isFile() && possibleJar.getName().endsWith(".jar")) {
WebResourceSet resourceSet = new JarResourceSet(webResourcesRoot, "/WEB-INF/classes", possibleJar.getCanonicalPath(),"/");
webResourcesRoot.addPostResources(resourceSet);
}
}
}
super.lifecycleEvent(event);
}
};
ctx.addLifecycleListener(ctxCfg);
This is an undocumented solution that works on Tomcat 8.0.23. Considering the complexity and difficulty of this I can't say it is a better solution than adding jars directly to ClassLoaders.

Ignoring web.xml when loading a WAR file with Jetty

I'm trying a self-executable WAR package with Jetty. It configures with web.xml by default. If a run-time option is given, I wanted to override web.xml by Java code-level configuration with ServletContextHandler#addServlet, #addEventListener, and ...
Can I ignore web.xml while loading a WAR package?
% java -jar foobar.jar # Use web.xml
% java -jar foobar.jar --customize=something # Use Java code to configure
// Example
WebAppContext webapp = new WebAppContext();
webapp.setWar(warLocation.toExternalForm());
webapp.setContextPath("/");
if ( /* has run-time options */ ) {
webapp.setWar(warLocation.toExternalForm()); // But, no load web.xml!
// Emulates web.xml.
webapp.addEventListener(...);
webapp.setInitParameter("resteasy.role.based.security", "true");
webapp.addFilter(...);
} else {
webapp.setWar(warLocation.toExternalForm()); // Loading web.xml.
}
Additional Question:
Before server.start() is called, classes under WEB-INF/ are not loaded. Can I do some configuration webapp.something() with some classes under WEB-INF/? (E.g. extend WebInfConfiguration or do a similar class-loading that WebInfConfiguration does?)
For example, I'd like to do something like:
webapp.addEventListener(new SomeClassUnderWebInf()));
webapp.addEventListener(someInjector.inject(SomeClassUnderWebInf.class));
before server.start().

Handle the WebAppContext Configuration yourself.
Eg:
private static class SelfConfiguration extends AbstractConfiguration
{
#Override
public void configure(WebAppContext context) throws Exception
{
// Emulates web.xml.
webapp.addEventListener(...);
webapp.setInitParameter("resteasy.role.based.security", "true");
webapp.addFilter(...);
}
}
public static void main(String[] args) throws Exception
{
Server server = new Server(8080);
WebAppContext webapp = new WebAppContext();
webapp.setContextPath("/");
if (useWebXml)
{
webapp.setConfigurationClasses(WebAppContext.getDefaultConfigurationClasses());
}
else
{
webapp.setConfigurations(new Configuration[] {
new SelfConfiguration()
});
}
webapp.setWar("path/to/my/test.war");
webapp.setParentLoaderPriority(true);
server.setHandler(webapp);
server.start();
server.join();
}