001/* 002 * Copyright 2012-2018 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * http://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.boot.builder; 018 019import java.lang.ref.WeakReference; 020 021import org.springframework.beans.BeansException; 022import org.springframework.boot.builder.ParentContextApplicationContextInitializer.ParentContextAvailableEvent; 023import org.springframework.context.ApplicationContext; 024import org.springframework.context.ApplicationContextAware; 025import org.springframework.context.ApplicationListener; 026import org.springframework.context.ConfigurableApplicationContext; 027import org.springframework.context.event.ContextClosedEvent; 028import org.springframework.core.Ordered; 029import org.springframework.util.ObjectUtils; 030 031/** 032 * Listener that closes the application context if its parent is closed. It listens for 033 * refresh events and grabs the current context from there, and then listens for closed 034 * events and propagates it down the hierarchy. 035 * 036 * @author Dave Syer 037 * @author Eric Bottard 038 */ 039public class ParentContextCloserApplicationListener 040 implements ApplicationListener<ParentContextAvailableEvent>, 041 ApplicationContextAware, Ordered { 042 043 private int order = Ordered.LOWEST_PRECEDENCE - 10; 044 045 private ApplicationContext context; 046 047 @Override 048 public int getOrder() { 049 return this.order; 050 } 051 052 @Override 053 public void setApplicationContext(ApplicationContext context) throws BeansException { 054 this.context = context; 055 } 056 057 @Override 058 public void onApplicationEvent(ParentContextAvailableEvent event) { 059 maybeInstallListenerInParent(event.getApplicationContext()); 060 } 061 062 private void maybeInstallListenerInParent(ConfigurableApplicationContext child) { 063 if (child == this.context 064 && child.getParent() instanceof ConfigurableApplicationContext) { 065 ConfigurableApplicationContext parent = (ConfigurableApplicationContext) child 066 .getParent(); 067 parent.addApplicationListener(createContextCloserListener(child)); 068 } 069 } 070 071 /** 072 * Subclasses may override to create their own subclass of ContextCloserListener. This 073 * still enforces the use of a weak reference. 074 * @param child the child context 075 * @return the {@link ContextCloserListener} to use 076 */ 077 protected ContextCloserListener createContextCloserListener( 078 ConfigurableApplicationContext child) { 079 return new ContextCloserListener(child); 080 } 081 082 /** 083 * {@link ApplicationListener} to close the context. 084 */ 085 protected static class ContextCloserListener 086 implements ApplicationListener<ContextClosedEvent> { 087 088 private WeakReference<ConfigurableApplicationContext> childContext; 089 090 public ContextCloserListener(ConfigurableApplicationContext childContext) { 091 this.childContext = new WeakReference<>(childContext); 092 } 093 094 @Override 095 public void onApplicationEvent(ContextClosedEvent event) { 096 ConfigurableApplicationContext context = this.childContext.get(); 097 if ((context != null) 098 && (event.getApplicationContext() == context.getParent()) 099 && context.isActive()) { 100 context.close(); 101 } 102 } 103 104 @Override 105 public boolean equals(Object obj) { 106 if (this == obj) { 107 return true; 108 } 109 if (obj == null) { 110 return false; 111 } 112 if (obj instanceof ContextCloserListener) { 113 ContextCloserListener other = (ContextCloserListener) obj; 114 return ObjectUtils.nullSafeEquals(this.childContext.get(), 115 other.childContext.get()); 116 } 117 return super.equals(obj); 118 } 119 120 @Override 121 public int hashCode() { 122 return ObjectUtils.nullSafeHashCode(this.childContext.get()); 123 } 124 125 } 126 127}