org.springframework.web.context.ContextLoader Maven / Gradle / Ivy
/*
* Copyright 2002-2023 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.web.context;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Properties;
import java.util.concurrent.ConcurrentHashMap;
import javax.servlet.ServletContext;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.beans.BeanUtils;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextException;
import org.springframework.context.ApplicationContextInitializer;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.core.GenericTypeResolver;
import org.springframework.core.annotation.AnnotationAwareOrderComparator;
import org.springframework.core.env.ConfigurableEnvironment;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.support.PropertiesLoaderUtils;
import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;
import org.springframework.util.StringUtils;
/**
* Performs the actual initialization work for the root application context.
* Called by {@link ContextLoaderListener}.
*
* Looks for a {@link #CONTEXT_CLASS_PARAM "contextClass"} parameter at the
* {@code web.xml} context-param level to specify the context class type, falling
* back to {@link org.springframework.web.context.support.XmlWebApplicationContext}
* if not found. With the default ContextLoader implementation, any context class
* specified needs to implement the {@link ConfigurableWebApplicationContext} interface.
*
*
Processes a {@link #CONFIG_LOCATION_PARAM "contextConfigLocation"} context-param
* and passes its value to the context instance, parsing it into potentially multiple
* file paths which can be separated by any number of commas and spaces, e.g.
* "WEB-INF/applicationContext1.xml, WEB-INF/applicationContext2.xml".
* Ant-style path patterns are supported as well, e.g.
* "WEB-INF/*Context.xml,WEB-INF/spring*.xml" or "WEB-INF/**/*Context.xml".
* If not explicitly specified, the context implementation is supposed to use a
* default location (with XmlWebApplicationContext: "/WEB-INF/applicationContext.xml").
*
*
Note: In case of multiple config locations, later bean definitions will
* override ones defined in previously loaded files, at least when using one of
* Spring's default ApplicationContext implementations. This can be leveraged
* to deliberately override certain bean definitions via an extra XML file.
*
*
Above and beyond loading the root application context, this class can optionally
* load or obtain and hook up a shared parent context to the root application context.
* See the {@link #loadParentContext(ServletContext)} method for more information.
*
*
As of Spring 3.1, {@code ContextLoader} supports injecting the root web
* application context via the {@link #ContextLoader(WebApplicationContext)}
* constructor, allowing for programmatic configuration in Servlet 3.0+ environments.
* See {@link org.springframework.web.WebApplicationInitializer} for usage examples.
*
* @author Juergen Hoeller
* @author Colin Sampaleanu
* @author Sam Brannen
* @since 17.02.2003
* @see ContextLoaderListener
* @see ConfigurableWebApplicationContext
* @see org.springframework.web.context.support.XmlWebApplicationContext
*/
public class ContextLoader {
/**
* Config param for the root WebApplicationContext id,
* to be used as serialization id for the underlying BeanFactory: {@value}.
*/
public static final String CONTEXT_ID_PARAM = "contextId";
/**
* Name of servlet context parameter (i.e., {@value}) that can specify the
* config location for the root context, falling back to the implementation's
* default otherwise.
* @see org.springframework.web.context.support.XmlWebApplicationContext#DEFAULT_CONFIG_LOCATION
*/
public static final String CONFIG_LOCATION_PARAM = "contextConfigLocation";
/**
* Config param for the root WebApplicationContext implementation class to use: {@value}.
* @see #determineContextClass(ServletContext)
*/
public static final String CONTEXT_CLASS_PARAM = "contextClass";
/**
* Config param for {@link ApplicationContextInitializer} classes to use
* for initializing the root web application context: {@value}.
* @see #customizeContext(ServletContext, ConfigurableWebApplicationContext)
*/
public static final String CONTEXT_INITIALIZER_CLASSES_PARAM = "contextInitializerClasses";
/**
* Config param for global {@link ApplicationContextInitializer} classes to use
* for initializing all web application contexts in the current application: {@value}.
* @see #customizeContext(ServletContext, ConfigurableWebApplicationContext)
*/
public static final String GLOBAL_INITIALIZER_CLASSES_PARAM = "globalInitializerClasses";
/**
* Any number of these characters are considered delimiters between
* multiple values in a single init-param String value.
*/
private static final String INIT_PARAM_DELIMITERS = ",; \t\n";
/**
* Name of the class path resource (relative to the ContextLoader class)
* that defines ContextLoader's default strategy names.
*/
private static final String DEFAULT_STRATEGIES_PATH = "ContextLoader.properties";
/**
* Map from (thread context) ClassLoader to corresponding 'current' WebApplicationContext.
*/
private static final Map currentContextPerThread =
new ConcurrentHashMap<>(1);
/**
* The 'current' WebApplicationContext, if the ContextLoader class is
* deployed in the web app ClassLoader itself.
*/
@Nullable
private static volatile WebApplicationContext currentContext;
@Nullable
private static Properties defaultStrategies;
/**
* The root WebApplicationContext instance that this loader manages.
*/
@Nullable
private WebApplicationContext context;
/** Actual ApplicationContextInitializer instances to apply to the context. */
private final List> contextInitializers =
new ArrayList<>();
/**
* Create a new {@code ContextLoader} that will create a web application context
* based on the "contextClass" and "contextConfigLocation" servlet context-params.
* See class-level documentation for details on default values for each.
* This constructor is typically used when declaring the {@code
* ContextLoaderListener} subclass as a {@code } within {@code web.xml}, as
* a no-arg constructor is required.
* The created application context will be registered into the ServletContext under
* the attribute name {@link WebApplicationContext#ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE}
* and subclasses are free to call the {@link #closeWebApplicationContext} method on
* container shutdown to close the application context.
* @see #ContextLoader(WebApplicationContext)
* @see #initWebApplicationContext(ServletContext)
* @see #closeWebApplicationContext(ServletContext)
*/
public ContextLoader() {
}
/**
* Create a new {@code ContextLoader} with the given application context. This
* constructor is useful in Servlet 3.0+ environments where instance-based
* registration of listeners is possible through the {@link ServletContext#addListener}
* API.
*
The context may or may not yet be {@linkplain
* ConfigurableApplicationContext#refresh() refreshed}. If it (a) is an implementation
* of {@link ConfigurableWebApplicationContext} and (b) has not
* already been refreshed (the recommended approach), then the following will occur:
*
* - If the given context has not already been assigned an {@linkplain
* ConfigurableApplicationContext#setId id}, one will be assigned to it
* - {@code ServletContext} and {@code ServletConfig} objects will be delegated to
* the application context
* - {@link #customizeContext} will be called
* - Any {@link ApplicationContextInitializer ApplicationContextInitializers} specified through the
* "contextInitializerClasses" init-param will be applied.
* - {@link ConfigurableApplicationContext#refresh refresh()} will be called
*
* If the context has already been refreshed or does not implement
* {@code ConfigurableWebApplicationContext}, none of the above will occur under the
* assumption that the user has performed these actions (or not) per his or her
* specific needs.
* See {@link org.springframework.web.WebApplicationInitializer} for usage examples.
*
In any case, the given application context will be registered into the
* ServletContext under the attribute name {@link
* WebApplicationContext#ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE} and subclasses are
* free to call the {@link #closeWebApplicationContext} method on container shutdown
* to close the application context.
* @param context the application context to manage
* @see #initWebApplicationContext(ServletContext)
* @see #closeWebApplicationContext(ServletContext)
*/
public ContextLoader(WebApplicationContext context) {
this.context = context;
}
/**
* Specify which {@link ApplicationContextInitializer} instances should be used
* to initialize the application context used by this {@code ContextLoader}.
* @since 4.2
* @see #configureAndRefreshWebApplicationContext
* @see #customizeContext
*/
@SuppressWarnings("unchecked")
public void setContextInitializers(@Nullable ApplicationContextInitializer... initializers) {
if (initializers != null) {
for (ApplicationContextInitializer initializer : initializers) {
this.contextInitializers.add((ApplicationContextInitializer) initializer);
}
}
}
/**
* Initialize Spring's web application context for the given servlet context,
* using the application context provided at construction time, or creating a new one
* according to the "{@link #CONTEXT_CLASS_PARAM contextClass}" and
* "{@link #CONFIG_LOCATION_PARAM contextConfigLocation}" context-params.
* @param servletContext current servlet context
* @return the new WebApplicationContext
* @see #ContextLoader(WebApplicationContext)
* @see #CONTEXT_CLASS_PARAM
* @see #CONFIG_LOCATION_PARAM
*/
public WebApplicationContext initWebApplicationContext(ServletContext servletContext) {
if (servletContext.getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE) != null) {
throw new IllegalStateException(
"Cannot initialize context because there is already a root application context present - " +
"check whether you have multiple ContextLoader* definitions in your web.xml!");
}
servletContext.log("Initializing Spring root WebApplicationContext");
Log logger = LogFactory.getLog(ContextLoader.class);
if (logger.isInfoEnabled()) {
logger.info("Root WebApplicationContext: initialization started");
}
long startTime = System.currentTimeMillis();
try {
// Store context in local instance variable, to guarantee that
// it is available on ServletContext shutdown.
if (this.context == null) {
this.context = createWebApplicationContext(servletContext);
}
if (this.context instanceof ConfigurableWebApplicationContext) {
ConfigurableWebApplicationContext cwac = (ConfigurableWebApplicationContext) this.context;
if (!cwac.isActive()) {
// The context has not yet been refreshed -> provide services such as
// setting the parent context, setting the application context id, etc
if (cwac.getParent() == null) {
// The context instance was injected without an explicit parent ->
// determine parent for root web application context, if any.
ApplicationContext parent = loadParentContext(servletContext);
cwac.setParent(parent);
}
configureAndRefreshWebApplicationContext(cwac, servletContext);
}
}
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, this.context);
ClassLoader ccl = Thread.currentThread().getContextClassLoader();
if (ccl == ContextLoader.class.getClassLoader()) {
currentContext = this.context;
}
else if (ccl != null) {
currentContextPerThread.put(ccl, this.context);
}
if (logger.isInfoEnabled()) {
long elapsedTime = System.currentTimeMillis() - startTime;
logger.info("Root WebApplicationContext initialized in " + elapsedTime + " ms");
}
return this.context;
}
catch (RuntimeException | Error ex) {
logger.error("Context initialization failed", ex);
servletContext.setAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE, ex);
throw ex;
}
}
/**
* Instantiate the root WebApplicationContext for this loader, either the
* default context class or a custom context class if specified.
* This implementation expects custom contexts to implement the
* {@link ConfigurableWebApplicationContext} interface.
* Can be overridden in subclasses.
*
In addition, {@link #customizeContext} gets called prior to refreshing the
* context, allowing subclasses to perform custom modifications to the context.
* @param sc current servlet context
* @return the root WebApplicationContext
* @see ConfigurableWebApplicationContext
*/
protected WebApplicationContext createWebApplicationContext(ServletContext sc) {
Class contextClass = determineContextClass(sc);
if (!ConfigurableWebApplicationContext.class.isAssignableFrom(contextClass)) {
throw new ApplicationContextException("Custom context class [" + contextClass.getName() +
"] is not of type [" + ConfigurableWebApplicationContext.class.getName() + "]");
}
return (ConfigurableWebApplicationContext) BeanUtils.instantiateClass(contextClass);
}
/**
* Return the WebApplicationContext implementation class to use, either the
* default XmlWebApplicationContext or a custom context class if specified.
* @param servletContext current servlet context
* @return the WebApplicationContext implementation class to use
* @see #CONTEXT_CLASS_PARAM
* @see org.springframework.web.context.support.XmlWebApplicationContext
*/
protected Class determineContextClass(ServletContext servletContext) {
String contextClassName = servletContext.getInitParameter(CONTEXT_CLASS_PARAM);
if (contextClassName != null) {
try {
return ClassUtils.forName(contextClassName, ClassUtils.getDefaultClassLoader());
}
catch (ClassNotFoundException ex) {
throw new ApplicationContextException(
"Failed to load custom context class [" + contextClassName + "]", ex);
}
}
else {
if (defaultStrategies == null) {
// Load default strategy implementations from properties file.
// This is currently strictly internal and not meant to be customized
// by application developers.
try {
ClassPathResource resource = new ClassPathResource(DEFAULT_STRATEGIES_PATH, ContextLoader.class);
defaultStrategies = PropertiesLoaderUtils.loadProperties(resource);
}
catch (IOException ex) {
throw new IllegalStateException("Could not load 'ContextLoader.properties': " + ex.getMessage());
}
}
contextClassName = defaultStrategies.getProperty(WebApplicationContext.class.getName());
try {
return ClassUtils.forName(contextClassName, ContextLoader.class.getClassLoader());
}
catch (ClassNotFoundException ex) {
throw new ApplicationContextException(
"Failed to load default context class [" + contextClassName + "]", ex);
}
}
}
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc) {
if (ObjectUtils.identityToString(wac).equals(wac.getId())) {
// The application context id is still set to its original default value
// -> assign a more useful id based on available information
String idParam = sc.getInitParameter(CONTEXT_ID_PARAM);
if (idParam != null) {
wac.setId(idParam);
}
else {
// Generate default id...
wac.setId(ConfigurableWebApplicationContext.APPLICATION_CONTEXT_ID_PREFIX +
ObjectUtils.getDisplayString(sc.getContextPath()));
}
}
wac.setServletContext(sc);
String configLocationParam = sc.getInitParameter(CONFIG_LOCATION_PARAM);
if (configLocationParam != null) {
wac.setConfigLocation(configLocationParam);
}
// The wac environment's #initPropertySources will be called in any case when the context
// is refreshed; do it eagerly here to ensure servlet property sources are in place for
// use in any post-processing or initialization that occurs below prior to #refresh
ConfigurableEnvironment env = wac.getEnvironment();
if (env instanceof ConfigurableWebEnvironment) {
((ConfigurableWebEnvironment) env).initPropertySources(sc, null);
}
customizeContext(sc, wac);
wac.refresh();
}
/**
* Customize the {@link ConfigurableWebApplicationContext} created by this
* ContextLoader after config locations have been supplied to the context
* but before the context is refreshed.
*
The default implementation {@linkplain #determineContextInitializerClasses(ServletContext)
* determines} what (if any) context initializer classes have been specified through
* {@linkplain #CONTEXT_INITIALIZER_CLASSES_PARAM context init parameters} and
* {@linkplain ApplicationContextInitializer#initialize invokes each} with the
* given web application context.
*
Any {@code ApplicationContextInitializers} implementing
* {@link org.springframework.core.Ordered Ordered} or marked with @{@link
* org.springframework.core.annotation.Order Order} will be sorted appropriately.
* @param sc the current servlet context
* @param wac the newly created application context
* @see #CONTEXT_INITIALIZER_CLASSES_PARAM
* @see ApplicationContextInitializer#initialize(ConfigurableApplicationContext)
*/
protected void customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac) {
List>> initializerClasses =
determineContextInitializerClasses(sc);
for (Class> initializerClass : initializerClasses) {
Class initializerContextClass =
GenericTypeResolver.resolveTypeArgument(initializerClass, ApplicationContextInitializer.class);
if (initializerContextClass != null && !initializerContextClass.isInstance(wac)) {
throw new ApplicationContextException(String.format(
"Could not apply context initializer [%s] since its generic parameter [%s] " +
"is not assignable from the type of application context used by this " +
"context loader: [%s]", initializerClass.getName(), initializerContextClass.getName(),
wac.getClass().getName()));
}
this.contextInitializers.add(BeanUtils.instantiateClass(initializerClass));
}
AnnotationAwareOrderComparator.sort(this.contextInitializers);
for (ApplicationContextInitializer initializer : this.contextInitializers) {
initializer.initialize(wac);
}
}
/**
* Return the {@link ApplicationContextInitializer} implementation classes to use
* if any have been specified by {@link #CONTEXT_INITIALIZER_CLASSES_PARAM}.
* @param servletContext current servlet context
* @see #CONTEXT_INITIALIZER_CLASSES_PARAM
*/
protected List>>
determineContextInitializerClasses(ServletContext servletContext) {
List>> classes =
new ArrayList<>();
String globalClassNames = servletContext.getInitParameter(GLOBAL_INITIALIZER_CLASSES_PARAM);
if (globalClassNames != null) {
for (String className : StringUtils.tokenizeToStringArray(globalClassNames, INIT_PARAM_DELIMITERS)) {
classes.add(loadInitializerClass(className));
}
}
String localClassNames = servletContext.getInitParameter(CONTEXT_INITIALIZER_CLASSES_PARAM);
if (localClassNames != null) {
for (String className : StringUtils.tokenizeToStringArray(localClassNames, INIT_PARAM_DELIMITERS)) {
classes.add(loadInitializerClass(className));
}
}
return classes;
}
@SuppressWarnings("unchecked")
private Class> loadInitializerClass(String className) {
try {
Class clazz = ClassUtils.forName(className, ClassUtils.getDefaultClassLoader());
if (!ApplicationContextInitializer.class.isAssignableFrom(clazz)) {
throw new ApplicationContextException(
"Initializer class does not implement ApplicationContextInitializer interface: " + clazz);
}
return (Class>) clazz;
}
catch (ClassNotFoundException ex) {
throw new ApplicationContextException("Failed to load context initializer class [" + className + "]", ex);
}
}
/**
* Template method with default implementation (which may be overridden by a
* subclass), to load or obtain an ApplicationContext instance which will be
* used as the parent context of the root WebApplicationContext. If the
* return value from the method is null, no parent context is set.
* The main reason to load a parent context here is to allow multiple root
* web application contexts to all be children of a shared EAR context, or
* alternately to also share the same parent context that is visible to
* EJBs. For pure web applications, there is usually no need to worry about
* having a parent context to the root web application context.
*
The default implementation simply returns {@code null}, as of 5.0.
* @param servletContext current servlet context
* @return the parent application context, or {@code null} if none
*/
@Nullable
protected ApplicationContext loadParentContext(ServletContext servletContext) {
return null;
}
/**
* Close Spring's web application context for the given servlet context.
*
If overriding {@link #loadParentContext(ServletContext)}, you may have
* to override this method as well.
* @param servletContext the ServletContext that the WebApplicationContext runs in
*/
public void closeWebApplicationContext(ServletContext servletContext) {
servletContext.log("Closing Spring root WebApplicationContext");
try {
if (this.context instanceof ConfigurableWebApplicationContext) {
((ConfigurableWebApplicationContext) this.context).close();
}
}
finally {
ClassLoader ccl = Thread.currentThread().getContextClassLoader();
if (ccl == ContextLoader.class.getClassLoader()) {
currentContext = null;
}
else if (ccl != null) {
currentContextPerThread.remove(ccl);
}
servletContext.removeAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
}
}
/**
* Obtain the Spring root web application context for the current thread
* (i.e. for the current thread's context ClassLoader, which needs to be
* the web application's ClassLoader).
* @return the current root web application context, or {@code null}
* if none found
* @see org.springframework.web.context.support.SpringBeanAutowiringSupport
*/
@Nullable
public static WebApplicationContext getCurrentWebApplicationContext() {
ClassLoader ccl = Thread.currentThread().getContextClassLoader();
if (ccl != null) {
WebApplicationContext ccpt = currentContextPerThread.get(ccl);
if (ccpt != null) {
return ccpt;
}
}
return currentContext;
}
}