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Remove inconsistent synchronization from EmbeddedWebApplicationContext
Previously, EmbeddedWebApplicationContext used synchronized, but did not do so consistently. It also synchronized on this so its lock was exposed outside of the class, creating a risk of deadlock if a caller synchronized incorrectly. Furthermore, not all fields on the class were sychronized so the class wasn't truly thread-safe. This commit attempts to rectify some of the problems above. The use of synchronized has been dropped in favour of using a volatile field for the embedded servlet container. Whenever this field is accessed, a local variable is used to "cache" the value thereby preventing a change on another thread from causing unwanted behaviour such as an NPE. Closes gh-4593
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@ -95,7 +95,7 @@ public class EmbeddedWebApplicationContext extends GenericWebApplicationContext
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*/
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public static final String DISPATCHER_SERVLET_NAME = ServletContextInitializerBeans.DISPATCHER_SERVLET_NAME;
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private EmbeddedServletContainer embeddedServletContainer;
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private volatile EmbeddedServletContainer embeddedServletContainer;
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private ServletConfig servletConfig;
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@ -138,10 +138,10 @@ public class EmbeddedWebApplicationContext extends GenericWebApplicationContext
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@Override
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protected void finishRefresh() {
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super.finishRefresh();
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startEmbeddedServletContainer();
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if (this.embeddedServletContainer != null) {
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publishEvent(new EmbeddedServletContainerInitializedEvent(this,
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this.embeddedServletContainer));
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EmbeddedServletContainer localContainer = startEmbeddedServletContainer();
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if (localContainer != null) {
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publishEvent(
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new EmbeddedServletContainerInitializedEvent(this, localContainer));
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}
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}
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@ -151,15 +151,17 @@ public class EmbeddedWebApplicationContext extends GenericWebApplicationContext
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stopAndReleaseEmbeddedServletContainer();
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}
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private synchronized void createEmbeddedServletContainer() {
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if (this.embeddedServletContainer == null && getServletContext() == null) {
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private void createEmbeddedServletContainer() {
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EmbeddedServletContainer localContainer = this.embeddedServletContainer;
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ServletContext localServletContext = getServletContext();
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if (localContainer == null && localServletContext == null) {
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EmbeddedServletContainerFactory containerFactory = getEmbeddedServletContainerFactory();
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this.embeddedServletContainer = containerFactory
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.getEmbeddedServletContainer(getSelfInitializer());
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}
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else if (getServletContext() != null) {
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else if (localServletContext != null) {
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try {
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getSelfInitializer().onStartup(getServletContext());
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getSelfInitializer().onStartup(localServletContext);
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}
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catch (ServletException ex) {
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throw new ApplicationContextException("Cannot initialize servlet context",
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@ -284,16 +286,19 @@ public class EmbeddedWebApplicationContext extends GenericWebApplicationContext
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}
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}
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private void startEmbeddedServletContainer() {
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if (this.embeddedServletContainer != null) {
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this.embeddedServletContainer.start();
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private EmbeddedServletContainer startEmbeddedServletContainer() {
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EmbeddedServletContainer localContainer = this.embeddedServletContainer;
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if (localContainer != null) {
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localContainer.start();
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}
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return localContainer;
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}
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private synchronized void stopAndReleaseEmbeddedServletContainer() {
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if (this.embeddedServletContainer != null) {
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private void stopAndReleaseEmbeddedServletContainer() {
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EmbeddedServletContainer localContainer = this.embeddedServletContainer;
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if (localContainer != null) {
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try {
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this.embeddedServletContainer.stop();
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localContainer.stop();
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this.embeddedServletContainer = null;
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}
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catch (Exception ex) {
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