io.logspace.jvm.agent.api.AgentControllerProvider Maven / Gradle / Ivy
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/**
* Logspace
* Copyright (c) 2015 Indoqa Software Design und Beratung GmbH. All rights reserved.
* This program and the accompanying materials are made available under the terms of
* the Eclipse Public License Version 1.0, which accompanies this distribution and
* is available at http://www.eclipse.org/legal/epl-v10.html.
*/
package io.logspace.jvm.agent.api;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.net.MalformedURLException;
import java.net.URL;
import java.text.MessageFormat;
import java.util.Arrays;
import io.logspace.jvm.agent.api.util.ConsoleWriter;
/**
* Factory for creating the {@link AgentController}.
*
* This class implements the lookup mechanism for find a {@link AgentControllerDescription} if none has been set programmatically:
*
* - Check the system-property 'logspace.config'. If a value is set, treat it as URL or file path and try to load the description
* using {@link #setDescription(URL)}.
* - If the file './logspace.json' exists, try to load the description using {@link #setDescription(URL)}
* - If the resource '/logspace-test.json' exists in classpath, try to load the description using {@link #setDescription(URL)}
* - If the resource '/logspace.json' exists in classpath, try to load the description using {@link #setDescription(URL)}
* - If the resource '/logspace-default.json' exists in classpath, try to load the description using {@link #setDescription(URL)}
*
*
* If none of these locations exist, initializing an {@link AgentController} will fail.
*
* Setting an AgentControllerDescription programmatically will override the default lookup mechanism.
*/
public final class AgentControllerProvider {
public static final String PROPERTY_LOGSPACE_CONFIG = "logspace.config";
private static final String[] CONFIG_LOCATIONS = {"/logspace-test.json", "/logspace.json", "/logspace-default.json"};
private static AgentController agentController;
private static AgentControllerDescription agentControllerDescription;
private AgentControllerProvider() {
// hide utility class constructor
}
/**
* Flush the current {@link AgentController}.
* This method does nothing if no AgentController is initialized.
*/
public static synchronized void flush() {
if (agentController != null) {
agentController.flush();
}
}
/**
* Get the currently configured {@link AgentController}.
* This method will initialize the AgentController if necessary.
*
* @return The current AgentController.
*/
public static synchronized AgentController getAgentController() {
if (agentController == null) {
agentController = initialize();
}
return agentController;
}
/**
* @return true if an {@link AgentController} is initialized, false otherwise.
*/
public static synchronized boolean isInitialized() {
return agentController != null;
}
/**
* Sets the {@link AgentControllerDescription} to be used for initializing the {@link AgentController}.
*
* This method will fail with an {@link AgentControllerInitializationException} if the AgentController has already been
* initialized.
* Calling this method will null will revert back to the default lookup mechanism.
*
* @param agentControllerDescription The AgentControllerDescription to be set.
*/
public static synchronized void setDescription(AgentControllerDescription agentControllerDescription) {
if (isInitialized()) {
throw new AgentControllerInitializationException(
"Cannot set a new description after the AgentController has already been initialized.");
}
AgentControllerProvider.agentControllerDescription = agentControllerDescription;
}
/**
* Set the {@link AgentControllerDescription} by reading it from the given {@link InputStream} and close the InputStream.
*
* This method expects the InputStream to provide a description in a format, that can be read by the
* {@link AgentControllerDescriptionFactory}.
* This method will fail with an {@link AgentControllerInitializationException} if the AgentController has already been initialized
* or the AgentControllerDescription could not be loaded from the InputStream.
*
* @param inputStream The InputStream to read the AgentControllerDescription from.
*/
public static synchronized void setDescription(InputStream inputStream) {
try {
setDescription(AgentControllerDescriptionFactory.fromJson(inputStream));
} catch (IOException ioex) {
throw new AgentControllerInitializationException("Could not load logspace configuration.", ioex);
} finally {
closeQuietly(inputStream);
}
}
/**
* Set the {@link AgentControllerDescription} by reading it from the given {@link URL}.
*
* This method expects the URL to point to a description in a format, that can be read by the
* {@link AgentControllerDescriptionFactory}.
* This method will fail with an {@link AgentControllerInitializationException} if the AgentController has already been initialized
* or the {@link AgentControllerDescription} could not be loaded from the URL.
*
* @param descriptionURL The URL to read the AgentControllerDescription from.
*/
public static synchronized void setDescription(URL descriptionURL) {
if (descriptionURL == null) {
return;
}
try {
setDescription(descriptionURL.openStream());
ConsoleWriter.writeSystem(MessageFormat.format("Loaded logspace configuration from ''{0}''.", descriptionURL));
} catch (IOException ioex) {
throw new AgentControllerInitializationException(
"Could not load logspace configuration from URL '" + descriptionURL + "'.", ioex);
}
}
/**
* Flush the current {@link AgentController} and shut it down.
* After a successful call to this method, {@link #isInitialized()} will return false and a new
* {@link AgentControllerDescription} can be set.
* A call to {@link #getAgentController()} will initialize a new AgentController, using the last AgentControllerDescription
* configured.
*
* This method does nothing if no AgentController is initialized.
*/
public static synchronized void shutdown() {
if (agentController == null) {
return;
}
agentController.flush();
agentController.shutdown();
agentController = null;
}
private static void closeQuietly(InputStream inputStream) {
if (inputStream == null) {
return;
}
try {
inputStream.close();
} catch (IOException e) {
// do nothing
}
}
private static Object executeConstructor(Constructor constructor, Object... arguments) {
try {
return constructor.newInstance(arguments);
} catch (Exception e) {
throw new AgentControllerInitializationException(
"Failed to instantiate Agent Controller of class '" + constructor.getDeclaringClass() + "'.", e);
}
}
private static Constructor getConstructor(Constructor[] constructors, Class... parameterTypes) {
for (Constructor eachConstructor : constructors) {
if (Arrays.equals(eachConstructor.getParameterTypes(), parameterTypes)) {
return eachConstructor;
}
}
return null;
}
private static boolean hasDescription() {
return agentControllerDescription != null;
}
private static AgentController initialize() {
initializeDescription();
Class agentControllerClass = loadClass(agentControllerDescription);
Constructor[] constructors = agentControllerClass.getConstructors();
Constructor constructor = getConstructor(constructors, AgentControllerDescription.class);
if (constructor != null) {
return (AgentController) executeConstructor(constructor, agentControllerDescription);
}
constructor = getConstructor(constructors);
if (constructor != null) {
return (AgentController) executeConstructor(constructor);
}
throw new AgentControllerInitializationException(
"Could not find a suitable constructor for AgentController '" + agentControllerClass + "'. Either a constructor accepting "
+ AgentControllerDescription.class + " or a default constructor is required.");
}
private static void initializeDescription() {
if (hasDescription()) {
return;
}
initializeDescriptionFromSetting();
if (hasDescription()) {
return;
}
initializeDescriptionFromFile();
if (hasDescription()) {
return;
}
initializeDescriptionFromClasspath();
if (!hasDescription()) {
throw new AgentControllerInitializationException("Could not find any description.");
}
}
private static void initializeDescriptionFromClasspath() {
for (String eachConfigLocation : CONFIG_LOCATIONS) {
if (hasDescription()) {
return;
}
setDescription(AgentControllerProvider.class.getResource(eachConfigLocation));
}
}
private static void initializeDescriptionFromFile() {
File file = new File("logspace.json");
if (!file.exists()) {
return;
}
try {
setDescription(file.toURI().toURL());
} catch (MalformedURLException e) {
// do nothing
}
}
private static void initializeDescriptionFromSetting() {
String logspaceConfig = System.getProperty(PROPERTY_LOGSPACE_CONFIG);
if (logspaceConfig == null) {
return;
}
try {
setDescription(new URL(logspaceConfig));
} catch (MalformedURLException e) {
// do nothing
}
if (hasDescription()) {
return;
}
// assume the location is a file path
File file = new File(logspaceConfig);
if (!file.exists()) {
throw new AgentControllerInitializationException(
"Could not load logspace configuration from the configured location '" + logspaceConfig + "'. Is the value correct?");
}
try {
setDescription(file.toURI().toURL());
} catch (MalformedURLException e) {
// do nothing
}
}
@SuppressWarnings("unchecked")
private static Class loadClass(AgentControllerDescription description) {
if (description.getClassName() == null) {
throw new AgentControllerInitializationException("The Agent Controller class is unconfigured.");
}
try {
return (Class) Class.forName(description.getClassName());
} catch (ClassNotFoundException cnfex) {
throw new AgentControllerInitializationException(
"Could not load Agent Controller class '" + description.getClassName() + "'.", cnfex);
}
}
}