ContextLoader (Spring Framework 5.1.0.RELEASE API)

java.lang.Object
- org.springframework.web.context.ContextLoader

Direct Known Subclasses:

ContextLoaderListener
```
public class ContextLoader
extends java.lang.Object
```
Performs the actual initialization work for the root application context. Called by ContextLoaderListener.
Looks for a "contextClass" parameter at the web.xml context-param level to specify the context class type, falling back to XmlWebApplicationContext if not found. With the default ContextLoader implementation, any context class specified needs to implement the ConfigurableWebApplicationContext interface.
Processes a "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 loadParentContext(ServletContext) method for more information.
As of Spring 3.1, ContextLoader supports injecting the root web application context via the ContextLoader(WebApplicationContext) constructor, allowing for programmatic configuration in Servlet 3.0+ environments. See WebApplicationInitializer for usage examples.

Since:

17.02.2003

Author:

Juergen Hoeller, Colin Sampaleanu, Sam Brannen

See Also:

ContextLoaderListener, ConfigurableWebApplicationContext, XmlWebApplicationContext

Field Summary

Fields
Modifier and Type	Field and Description
`static java.lang.String`	`CONFIG_LOCATION_PARAM` Name of servlet context parameter (i.e., "contextConfigLocation") that can specify the config location for the root context, falling back to the implementation's default otherwise.
`static java.lang.String`	`CONTEXT_CLASS_PARAM` Config param for the root WebApplicationContext implementation class to use: "contextClass".
`static java.lang.String`	`CONTEXT_ID_PARAM` Config param for the root WebApplicationContext id, to be used as serialization id for the underlying BeanFactory: "contextId".
`static java.lang.String`	`CONTEXT_INITIALIZER_CLASSES_PARAM` Config param for `ApplicationContextInitializer` classes to use for initializing the root web application context: "contextInitializerClasses".
`static java.lang.String`	`GLOBAL_INITIALIZER_CLASSES_PARAM` Config param for global `ApplicationContextInitializer` classes to use for initializing all web application contexts in the current application: "globalInitializerClasses".

Constructor Summary

Constructors
Constructor and Description
`ContextLoader()` Create a new `ContextLoader` that will create a web application context based on the "contextClass" and "contextConfigLocation" servlet context-params.
`ContextLoader(WebApplicationContext context)` Create a new `ContextLoader` with the given application context.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`closeWebApplicationContext(ServletContext servletContext)` Close Spring's web application context for the given servlet context.
`protected void`	`configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac, ServletContext sc)`
`protected WebApplicationContext`	`createWebApplicationContext(ServletContext sc)` Instantiate the root WebApplicationContext for this loader, either the default context class or a custom context class if specified.
`protected void`	`customizeContext(ServletContext sc, ConfigurableWebApplicationContext wac)` Customize the `ConfigurableWebApplicationContext` created by this ContextLoader after config locations have been supplied to the context but before the context is refreshed.
`protected java.lang.Class<?>`	`determineContextClass(ServletContext servletContext)` Return the WebApplicationContext implementation class to use, either the default XmlWebApplicationContext or a custom context class if specified.
`protected java.util.List<java.lang.Class<ApplicationContextInitializer<ConfigurableApplicationContext>>>`	`determineContextInitializerClasses(ServletContext servletContext)` Return the `ApplicationContextInitializer` implementation classes to use if any have been specified by `CONTEXT_INITIALIZER_CLASSES_PARAM`.
`static WebApplicationContext`	`getCurrentWebApplicationContext()` Obtain the Spring root web application context for the current thread (i.e.
`WebApplicationContext`	`initWebApplicationContext(ServletContext servletContext)` 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 "`contextClass`" and "`contextConfigLocation`" context-params.
`protected ApplicationContext`	`loadParentContext(ServletContext servletContext)` 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.
`void`	`setContextInitializers(ApplicationContextInitializer<?>... initializers)` Specify which `ApplicationContextInitializer` instances should be used to initialize the application context used by this `ContextLoader`.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - CONTEXT_ID_PARAM
```
public static final java.lang.String CONTEXT_ID_PARAM
```
    Config param for the root WebApplicationContext id, to be used as serialization id for the underlying BeanFactory: "contextId".
    
    See Also:
    
    Constant Field Values
  - CONFIG_LOCATION_PARAM
```
public static final java.lang.String CONFIG_LOCATION_PARAM
```
    Name of servlet context parameter (i.e., "contextConfigLocation") that can specify the config location for the root context, falling back to the implementation's default otherwise.
    
    See Also:
    
    XmlWebApplicationContext.DEFAULT_CONFIG_LOCATION, Constant Field Values
  - CONTEXT_CLASS_PARAM
```
public static final java.lang.String CONTEXT_CLASS_PARAM
```
    Config param for the root WebApplicationContext implementation class to use: "contextClass".
    
    See Also:
    
    determineContextClass(ServletContext), Constant Field Values
  - CONTEXT_INITIALIZER_CLASSES_PARAM
```
public static final java.lang.String CONTEXT_INITIALIZER_CLASSES_PARAM
```
    Config param for ApplicationContextInitializer classes to use for initializing the root web application context: "contextInitializerClasses".
    
    See Also:
    
    customizeContext(ServletContext, ConfigurableWebApplicationContext), Constant Field Values
  - GLOBAL_INITIALIZER_CLASSES_PARAM
```
public static final java.lang.String GLOBAL_INITIALIZER_CLASSES_PARAM
```
    Config param for global ApplicationContextInitializer classes to use for initializing all web application contexts in the current application: "globalInitializerClasses".
    
    See Also:
    
    customizeContext(ServletContext, ConfigurableWebApplicationContext), Constant Field Values
- Constructor Detail
  - ContextLoader
```
public ContextLoader()
```
    Create a new 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 ContextLoaderListener subclass as a <listener> within web.xml, as a no-arg constructor is required.
    The created application context will be registered into the ServletContext under the attribute name WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE and subclasses are free to call the closeWebApplicationContext(javax.servlet.ServletContext) method on container shutdown to close the application context.
    
    See Also:
    
    ContextLoader(WebApplicationContext), initWebApplicationContext(ServletContext), closeWebApplicationContext(ServletContext)
  - ContextLoader
```
public ContextLoader(WebApplicationContext context)
```
    Create a new 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 ServletContext.addListener(java.lang.String) API.
    The context may or may not yet be refreshed. If it (a) is an implementation of 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 id, one will be assigned to it
    - ServletContext and ServletConfig objects will be delegated to the application context
    - customizeContext(javax.servlet.ServletContext, org.springframework.web.context.ConfigurableWebApplicationContext) will be called
    - Any ApplicationContextInitializers specified through the "contextInitializerClasses" init-param will be applied.
    - refresh() will be called
    If the context has already been refreshed or does not implement 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 WebApplicationInitializer for usage examples.
    In any case, the given application context will be registered into the ServletContext under the attribute name WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE and subclasses are free to call the closeWebApplicationContext(javax.servlet.ServletContext) method on container shutdown to close the application context.
    Parameters:
    
    context - the application context to manage
    
    See Also:
    
    initWebApplicationContext(ServletContext), closeWebApplicationContext(ServletContext)
- Method Detail
  - setContextInitializers
```
public void setContextInitializers(@Nullable
                                   ApplicationContextInitializer<?>... initializers)
```
    Specify which ApplicationContextInitializer instances should be used to initialize the application context used by this ContextLoader.
    
    Since:
    
    4.2
    
    See Also:
    
    configureAndRefreshWebApplicationContext(org.springframework.web.context.ConfigurableWebApplicationContext, javax.servlet.ServletContext), customizeContext(javax.servlet.ServletContext, org.springframework.web.context.ConfigurableWebApplicationContext)
  - initWebApplicationContext
```
public WebApplicationContext initWebApplicationContext(ServletContext servletContext)
```
    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 "contextClass" and "contextConfigLocation" context-params.
    
    Parameters:
    
    servletContext - current servlet context
    
    Returns:
    
    the new WebApplicationContext
    
    See Also:
    
    ContextLoader(WebApplicationContext), CONTEXT_CLASS_PARAM, CONFIG_LOCATION_PARAM
  - createWebApplicationContext
```
protected WebApplicationContext createWebApplicationContext(ServletContext sc)
```
    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 ConfigurableWebApplicationContext interface. Can be overridden in subclasses.
    In addition, customizeContext(javax.servlet.ServletContext, org.springframework.web.context.ConfigurableWebApplicationContext) gets called prior to refreshing the context, allowing subclasses to perform custom modifications to the context.
    
    Parameters:
    
    sc - current servlet context
    
    Returns:
    
    the root WebApplicationContext
    
    See Also:
    
    ConfigurableWebApplicationContext
  - determineContextClass
```
protected java.lang.Class<?> determineContextClass(ServletContext servletContext)
```
    Return the WebApplicationContext implementation class to use, either the default XmlWebApplicationContext or a custom context class if specified.
    
    Parameters:
    
    servletContext - current servlet context
    
    Returns:
    
    the WebApplicationContext implementation class to use
    
    See Also:
    
    CONTEXT_CLASS_PARAM, XmlWebApplicationContext
  - configureAndRefreshWebApplicationContext
```
protected void configureAndRefreshWebApplicationContext(ConfigurableWebApplicationContext wac,
                                                        ServletContext sc)
```
  - customizeContext
```
protected void customizeContext(ServletContext sc,
                                ConfigurableWebApplicationContext wac)
```
    Customize the ConfigurableWebApplicationContext created by this ContextLoader after config locations have been supplied to the context but before the context is refreshed.
    The default implementation determines what (if any) context initializer classes have been specified through context init parameters and invokes each with the given web application context.
    Any ApplicationContextInitializers implementing Ordered or marked with @Order will be sorted appropriately.
    
    Parameters:
    
    sc - the current servlet context
    
    wac - the newly created application context
    
    See Also:
    
    CONTEXT_INITIALIZER_CLASSES_PARAM, ApplicationContextInitializer.initialize(ConfigurableApplicationContext)
  - determineContextInitializerClasses
```
protected java.util.List<java.lang.Class<ApplicationContextInitializer<ConfigurableApplicationContext>>> determineContextInitializerClasses(ServletContext servletContext)
```
    Return the ApplicationContextInitializer implementation classes to use if any have been specified by CONTEXT_INITIALIZER_CLASSES_PARAM.
    
    Parameters:
    
    servletContext - current servlet context
    
    See Also:
    
    CONTEXT_INITIALIZER_CLASSES_PARAM
  - loadParentContext
```
@Nullable
protected ApplicationContext loadParentContext(ServletContext servletContext)
```
    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 null, as of 5.0.
    
    Parameters:
    
    servletContext - current servlet context
    
    Returns:
    
    the parent application context, or null if none
  - closeWebApplicationContext
```
public void closeWebApplicationContext(ServletContext servletContext)
```
    Close Spring's web application context for the given servlet context.
    If overriding loadParentContext(ServletContext), you may have to override this method as well.
    
    Parameters:
    
    servletContext - the ServletContext that the WebApplicationContext runs in
  - getCurrentWebApplicationContext
```
@Nullable
public static WebApplicationContext getCurrentWebApplicationContext()
```
    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).
    
    Returns:
    
    the current root web application context, or null if none found
    
    See Also:
    
    SpringBeanAutowiringSupport

Class ContextLoader

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

CONTEXT_ID_PARAM

CONFIG_LOCATION_PARAM

CONTEXT_CLASS_PARAM

CONTEXT_INITIALIZER_CLASSES_PARAM

GLOBAL_INITIALIZER_CLASSES_PARAM

Constructor Detail

ContextLoader

ContextLoader

Method Detail

setContextInitializers

initWebApplicationContext

createWebApplicationContext

determineContextClass

configureAndRefreshWebApplicationContext

customizeContext

determineContextInitializerClasses

loadParentContext

closeWebApplicationContext

getCurrentWebApplicationContext