Java tutorial
/* * Copyright 2002-2018 the original author or authors. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * https://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package org.springframework.context.support; import java.lang.management.ManagementFactory; import java.util.Collections; import java.util.Iterator; import java.util.LinkedHashSet; import java.util.Set; import javax.management.MBeanServer; import javax.management.ObjectName; import org.springframework.beans.factory.config.BeanDefinition; import org.springframework.beans.factory.config.ConfigurableBeanFactory; import org.springframework.beans.factory.config.ConfigurableListableBeanFactory; import org.springframework.context.ApplicationContext; import org.springframework.context.ApplicationContextAware; import org.springframework.context.ApplicationContextException; import org.springframework.context.ConfigurableApplicationContext; import org.springframework.lang.Nullable; import org.springframework.util.Assert; import org.springframework.util.StringUtils; /** * Adapter for live beans view exposure, building a snapshot of current beans * and their dependencies from either a local {@code ApplicationContext} (with a * local {@code LiveBeansView} bean definition) or all registered ApplicationContexts * (driven by the {@value #MBEAN_DOMAIN_PROPERTY_NAME} environment property). * * <p>Note: This feature is still in beta and primarily designed for use with * Spring Tool Suite 3.1 and higher. * * @author Juergen Hoeller * @author Stephane Nicoll * @since 3.2 * @see #getSnapshotAsJson() * @see org.springframework.web.context.support.LiveBeansViewServlet */ public class LiveBeansView implements LiveBeansViewMBean, ApplicationContextAware { /** * The "MBean Domain" property name. */ public static final String MBEAN_DOMAIN_PROPERTY_NAME = "spring.liveBeansView.mbeanDomain"; /** * The MBean application key. */ public static final String MBEAN_APPLICATION_KEY = "application"; private static final Set<ConfigurableApplicationContext> applicationContexts = new LinkedHashSet<>(); @Nullable private static String applicationName; static void registerApplicationContext(ConfigurableApplicationContext applicationContext) { String mbeanDomain = applicationContext.getEnvironment().getProperty(MBEAN_DOMAIN_PROPERTY_NAME); if (mbeanDomain != null) { synchronized (applicationContexts) { if (applicationContexts.isEmpty()) { try { MBeanServer server = ManagementFactory.getPlatformMBeanServer(); applicationName = applicationContext.getApplicationName(); server.registerMBean(new LiveBeansView(), new ObjectName(mbeanDomain, MBEAN_APPLICATION_KEY, applicationName)); } catch (Throwable ex) { throw new ApplicationContextException("Failed to register LiveBeansView MBean", ex); } } applicationContexts.add(applicationContext); } } } static void unregisterApplicationContext(ConfigurableApplicationContext applicationContext) { synchronized (applicationContexts) { if (applicationContexts.remove(applicationContext) && applicationContexts.isEmpty()) { try { MBeanServer server = ManagementFactory.getPlatformMBeanServer(); String mbeanDomain = applicationContext.getEnvironment() .getProperty(MBEAN_DOMAIN_PROPERTY_NAME); if (mbeanDomain != null) { server.unregisterMBean(new ObjectName(mbeanDomain, MBEAN_APPLICATION_KEY, applicationName)); } } catch (Throwable ex) { throw new ApplicationContextException("Failed to unregister LiveBeansView MBean", ex); } finally { applicationName = null; } } } } @Nullable private ConfigurableApplicationContext applicationContext; @Override public void setApplicationContext(ApplicationContext applicationContext) { Assert.isTrue(applicationContext instanceof ConfigurableApplicationContext, "ApplicationContext does not implement ConfigurableApplicationContext"); this.applicationContext = (ConfigurableApplicationContext) applicationContext; } /** * Generate a JSON snapshot of current beans and their dependencies, * finding all active ApplicationContexts through {@link #findApplicationContexts()}, * then delegating to {@link #generateJson(java.util.Set)}. */ @Override public String getSnapshotAsJson() { Set<ConfigurableApplicationContext> contexts; if (this.applicationContext != null) { contexts = Collections.singleton(this.applicationContext); } else { contexts = findApplicationContexts(); } return generateJson(contexts); } /** * Find all applicable ApplicationContexts for the current application. * <p>Called if no specific ApplicationContext has been set for this LiveBeansView. * @return the set of ApplicationContexts */ protected Set<ConfigurableApplicationContext> findApplicationContexts() { synchronized (applicationContexts) { return new LinkedHashSet<>(applicationContexts); } } /** * Actually generate a JSON snapshot of the beans in the given ApplicationContexts. * <p>This implementation doesn't use any JSON parsing libraries in order to avoid * third-party library dependencies. It produces an array of context description * objects, each containing a context and parent attribute as well as a beans * attribute with nested bean description objects. Each bean object contains a * bean, scope, type and resource attribute, as well as a dependencies attribute * with a nested array of bean names that the present bean depends on. * @param contexts the set of ApplicationContexts * @return the JSON document */ protected String generateJson(Set<ConfigurableApplicationContext> contexts) { StringBuilder result = new StringBuilder("[\n"); for (Iterator<ConfigurableApplicationContext> it = contexts.iterator(); it.hasNext();) { ConfigurableApplicationContext context = it.next(); result.append("{\n\"context\": \"").append(context.getId()).append("\",\n"); if (context.getParent() != null) { result.append("\"parent\": \"").append(context.getParent().getId()).append("\",\n"); } else { result.append("\"parent\": null,\n"); } result.append("\"beans\": [\n"); ConfigurableListableBeanFactory bf = context.getBeanFactory(); String[] beanNames = bf.getBeanDefinitionNames(); boolean elementAppended = false; for (String beanName : beanNames) { BeanDefinition bd = bf.getBeanDefinition(beanName); if (isBeanEligible(beanName, bd, bf)) { if (elementAppended) { result.append(",\n"); } result.append("{\n\"bean\": \"").append(beanName).append("\",\n"); result.append("\"aliases\": "); appendArray(result, bf.getAliases(beanName)); result.append(",\n"); String scope = bd.getScope(); if (!StringUtils.hasText(scope)) { scope = BeanDefinition.SCOPE_SINGLETON; } result.append("\"scope\": \"").append(scope).append("\",\n"); Class<?> beanType = bf.getType(beanName); if (beanType != null) { result.append("\"type\": \"").append(beanType.getName()).append("\",\n"); } else { result.append("\"type\": null,\n"); } result.append("\"resource\": \"").append(getEscapedResourceDescription(bd)).append("\",\n"); result.append("\"dependencies\": "); appendArray(result, bf.getDependenciesForBean(beanName)); result.append("\n}"); elementAppended = true; } } result.append("]\n"); result.append("}"); if (it.hasNext()) { result.append(",\n"); } } result.append("]"); return result.toString(); } /** * Determine whether the specified bean is eligible for inclusion in the * LiveBeansView JSON snapshot. * @param beanName the name of the bean * @param bd the corresponding bean definition * @param bf the containing bean factory * @return {@code true} if the bean is to be included; {@code false} otherwise */ protected boolean isBeanEligible(String beanName, BeanDefinition bd, ConfigurableBeanFactory bf) { return (bd.getRole() != BeanDefinition.ROLE_INFRASTRUCTURE && (!bd.isLazyInit() || bf.containsSingleton(beanName))); } /** * Determine a resource description for the given bean definition and * apply basic JSON escaping (backslashes, double quotes) to it. * @param bd the bean definition to build the resource description for * @return the JSON-escaped resource description */ @Nullable protected String getEscapedResourceDescription(BeanDefinition bd) { String resourceDescription = bd.getResourceDescription(); if (resourceDescription == null) { return null; } StringBuilder result = new StringBuilder(resourceDescription.length() + 16); for (int i = 0; i < resourceDescription.length(); i++) { char character = resourceDescription.charAt(i); if (character == '\\') { result.append('/'); } else if (character == '"') { result.append("\\").append('"'); } else { result.append(character); } } return result.toString(); } private void appendArray(StringBuilder result, String[] arr) { result.append('['); if (arr.length > 0) { result.append('\"'); } result.append(StringUtils.arrayToDelimitedString(arr, "\", \"")); if (arr.length > 0) { result.append('\"'); } result.append(']'); } }