org.apache.catalina.loader

Class WebappClassLoader

Implemented Interfaces:
Lifecycle, Reloader

public class WebappClassLoader
extends URLClassLoader
implements Reloader, Lifecycle

Specialized web application class loader.

This class loader is a full reimplementation of the URLClassLoader from the JDK. It is desinged to be fully compatible with a normal URLClassLoader, although its internal behavior may be completely different.

IMPLEMENTATION NOTE - This class loader faithfully follows the delegation model recommended in the specification. The system class loader will be queried first, then the local repositories, and only then delegation to the parent class loader will occur. This allows the web application to override any shared class except the classes from J2SE. Special handling is provided from the JAXP XML parser interfaces, the JNDI interfaces, and the classes from the servlet API, which are never loaded from the webapp repository.

IMPLEMENTATION NOTE - Due to limitations in Jasper compilation technology, any repository which contains classes from the servlet API will be ignored by the class loader.

IMPLEMENTATION NOTE - The class loader generates source URLs which include the full JAR URL when a class is loaded from a JAR file, which allows setting security permission at the class level, even when a class is contained inside a JAR.

IMPLEMENTATION NOTE - Local repositories are searched in the order they are added via the initial constructor and/or any subsequent calls to addRepository() or addJar().

IMPLEMENTATION NOTE - No check for sealing violations or security is made unless a security manager is present.

Version:
$Revision: 1.34.2.1 $ $Date: 2004/10/05 16:29:01 $

Authors:
Remy Maucherat
Craig R. McClanahan

Nested Class Summary

protected class
WebappClassLoader.PrivilegedFindResource

Field Summary

protected int
debug
The debugging detail level of this component.
protected boolean
delegate
Should this class loader delegate to the parent class loader before searching its own repositories (i.e.
protected File[]
files
Repositories translated as path in the work directory (for Jasper originally), but which is used to generate fake URLs should getURLs be called.
protected boolean
hasExternalRepositories
Has external repositories.
protected JarFile[]
jarFiles
The list of JARs, in the order they should be searched for locally loaded classes or resources.
protected String[]
jarNames
The list of JARs, in the order they should be searched for locally loaded classes or resources.
protected String
jarPath
The path which will be monitored for added Jar files.
protected File[]
jarRealFiles
The list of JARs, in the order they should be searched for locally loaded classes or resources.
protected long
lastJarAccessed
Last time a JAR was accessed.
protected long[]
lastModifiedDates
The list of JARs last modified dates, in the order they should be searched for locally loaded classes or resources.
protected HashMap
notFoundResources
The list of not found resources.
protected String[]
paths
The list of resources which should be checked when checking for modifications.
protected String[]
repositories
The list of local repositories, in the order they should be searched for locally loaded classes or resources.
protected URL[]
repositoryURLs
Repositories URLs, used to cache the result of getURLs.
protected HashMap
resourceEntries
The cache of ResourceEntry for classes and resources we have loaded, keyed by resource name.
protected DirContext
resources
Associated directory context giving access to the resources in this webapp.
protected static StringManager
sm
The string manager for this package.
protected boolean
started
Has this component been started?

Fields inherited from interface org.apache.catalina.Lifecycle

AFTER_START_EVENT, AFTER_STOP_EVENT, BEFORE_START_EVENT, BEFORE_STOP_EVENT, START_EVENT, STOP_EVENT

Constructor Summary

WebappClassLoader()
Construct a new ClassLoader with no defined repositories and no parent ClassLoader.
WebappClassLoader(ClassLoader parent)
Construct a new ClassLoader with no defined repositories and no parent ClassLoader.

Method Summary

void
addLifecycleListener(LifecycleListener listener)
Add a lifecycle event listener to this component.
void
addPermission(Permission permission)
If there is a Java SecurityManager create a Permission.
void
addPermission(String path)
If there is a Java SecurityManager create a read FilePermission or JndiPermission for the file directory path.
void
addPermission(URL url)
If there is a Java SecurityManager create a read FilePermission or JndiPermission for URL.
void
addRepository(String repository)
Add a new repository to the set of places this ClassLoader can look for classes to be loaded.
protected void
addURL(URL url)
Add the specified URL to the classloader.
void
closeJARs(boolean force)
Used to periodically signal to the classloader to release JAR resources.
protected static void
deleteDir(File dir)
Delete the specified directory, including all of its contents and subdirectories recursively.
protected boolean
filter(String name)
Filter classes.
Class
findClass(String name)
Find the specified class in our local repositories, if possible.
protected Class
findClassInternal(String name)
Find specified class in local repositories.
LifecycleListener[]
findLifecycleListeners()
Get the lifecycle listeners associated with this lifecycle.
protected Class
findLoadedClass0(String name)
Finds the class with the given name if it has previously been loaded and cached by this class loader, and return the Class object.
protected InputStream
findLoadedResource(String name)
Finds the resource with the given name if it has previously been loaded and cached by this class loader, and return an input stream to the resource data.
String[]
findRepositories()
Return a String array of the current repositories for this class loader.
URL
findResource(String name)
Find the specified resource in our local repository, and return a URL refering to it, or null if this resource cannot be found.
protected ResourceEntry
findResourceInternal(String name, String path)
Find specified resource in local repositories.
Enumeration
findResources(String name)
Return an enumeration of URLs representing all of the resources with the given name.
int
getDebug()
Return the debugging detail level for this component.
boolean
getDelegate()
Return the "delegate first" flag for this class loader.
String
getJarPath()
Return the JAR path.
protected PermissionCollection
getPermissions(CodeSource codeSource)
Get the Permissions for a CodeSource.
URL
getResource(String name)
Find the resource with the given name.
InputStream
getResourceAsStream(String name)
Find the resource with the given name, and return an input stream that can be used for reading it.
DirContext
getResources()
Get associated resources.
protected URL
getURI(File file)
Get URL.
protected URL
getURL(File file)
Get URL.
URL[]
getURLs()
Returns the search path of URLs for loading classes and resources.
protected boolean
isPackageSealed(String name, Manifest man)
Returns true if the specified package name is sealed according to the given manifest.
Class
loadClass(String name)
Load the class with the specified name.
Class
loadClass(String name, boolean resolve)
Load the class with the specified name, searching using the following algorithm until it finds and returns the class.
boolean
modified()
Have one or more classes or resources been modified so that a reload is appropriate?
protected void
openJARs()
Used to periodically signal to the classloader to release JAR resources.
protected void
refreshPolicy()
Refresh the system policy file, to pick up eventual changes.
void
removeLifecycleListener(LifecycleListener listener)
Remove a lifecycle event listener from this component.
void
setDebug(int debug)
Set the debugging detail level for this component.
void
setDelegate(boolean delegate)
Set the "delegate first" flag for this class loader.
void
setJarPath(String jarPath)
Change the Jar path.
void
setResources(DirContext resources)
Set associated resources.
void
setWorkDir(File workDir)
Change the work directory.
void
start()
Start the class loader.
void
stop()
Stop the class loader.
String
toString()
Render a String representation of this object.
protected boolean
validate(String name)
Validate a classname.

Field Details

debug

protected int debug
The debugging detail level of this component.


delegate

protected boolean delegate
Should this class loader delegate to the parent class loader before searching its own repositories (i.e. the usual Java2 delegation model)? If set to false, this class loader will search its own repositories first, and delegate to the parent only if the class or resource is not found locally.


files

protected File[] files
Repositories translated as path in the work directory (for Jasper originally), but which is used to generate fake URLs should getURLs be called.


hasExternalRepositories

protected boolean hasExternalRepositories
Has external repositories.


jarFiles

protected JarFile[] jarFiles
The list of JARs, in the order they should be searched for locally loaded classes or resources.


jarNames

protected String[] jarNames
The list of JARs, in the order they should be searched for locally loaded classes or resources.


jarPath

protected String jarPath
The path which will be monitored for added Jar files.


jarRealFiles

protected File[] jarRealFiles
The list of JARs, in the order they should be searched for locally loaded classes or resources.


lastJarAccessed

protected long lastJarAccessed
Last time a JAR was accessed.


lastModifiedDates

protected long[] lastModifiedDates
The list of JARs last modified dates, in the order they should be searched for locally loaded classes or resources.


notFoundResources

protected HashMap notFoundResources
The list of not found resources.


paths

protected String[] paths
The list of resources which should be checked when checking for modifications.


repositories

protected String[] repositories
The list of local repositories, in the order they should be searched for locally loaded classes or resources.


repositoryURLs

protected URL[] repositoryURLs
Repositories URLs, used to cache the result of getURLs.


resourceEntries

protected HashMap resourceEntries
The cache of ResourceEntry for classes and resources we have loaded, keyed by resource name.


resources

protected DirContext resources
Associated directory context giving access to the resources in this webapp.


sm

protected static final StringManager sm
The string manager for this package.


started

protected boolean started
Has this component been started?

Constructor Details

WebappClassLoader

public WebappClassLoader()
Construct a new ClassLoader with no defined repositories and no parent ClassLoader.


WebappClassLoader

public WebappClassLoader(ClassLoader parent)
Construct a new ClassLoader with no defined repositories and no parent ClassLoader.

Method Details

addLifecycleListener

public void addLifecycleListener(LifecycleListener listener)
Add a lifecycle event listener to this component.
Specified by:
addLifecycleListener in interface Lifecycle

Parameters:
listener - The listener to add


addPermission

public void addPermission(Permission permission)
If there is a Java SecurityManager create a Permission.

Parameters:


addPermission

public void addPermission(String path)
If there is a Java SecurityManager create a read FilePermission or JndiPermission for the file directory path.

Parameters:
path - file directory path


addPermission

public void addPermission(URL url)
If there is a Java SecurityManager create a read FilePermission or JndiPermission for URL.

Parameters:
url - URL for a file or directory on local system


addRepository

public void addRepository(String repository)
Add a new repository to the set of places this ClassLoader can look for classes to be loaded.
Specified by:
addRepository in interface Reloader

Parameters:
repository - Name of a source of classes to be loaded, such as a directory pathname, a JAR file pathname, or a ZIP file pathname


addURL

protected void addURL(URL url)
Add the specified URL to the classloader.


closeJARs

public void closeJARs(boolean force)
Used to periodically signal to the classloader to release JAR resources.


deleteDir

protected static void deleteDir(File dir)
Delete the specified directory, including all of its contents and subdirectories recursively.

Parameters:
dir - File object representing the directory to be deleted


filter

protected boolean filter(String name)
Filter classes.

Parameters:
name - class name

Returns:
true if the class should be filtered


findClass

public Class findClass(String name)
            throws ClassNotFoundException
Find the specified class in our local repositories, if possible. If not found, throw ClassNotFoundException.

Parameters:
name - Name of the class to be loaded


findClassInternal

protected Class findClassInternal(String name)
            throws ClassNotFoundException
Find specified class in local repositories.

Returns:
the loaded class, or null if the class isn't found


findLifecycleListeners

public LifecycleListener[] findLifecycleListeners()
Get the lifecycle listeners associated with this lifecycle. If this Lifecycle has no listeners registered, a zero-length array is returned.
Specified by:
findLifecycleListeners in interface Lifecycle


findLoadedClass0

protected Class findLoadedClass0(String name)
Finds the class with the given name if it has previously been loaded and cached by this class loader, and return the Class object. If this class has not been cached, return null.

Parameters:
name - Name of the resource to return


findLoadedResource

protected InputStream findLoadedResource(String name)
Finds the resource with the given name if it has previously been loaded and cached by this class loader, and return an input stream to the resource data. If this resource has not been cached, return null.

Parameters:
name - Name of the resource to return


findRepositories

public String[] findRepositories()
Return a String array of the current repositories for this class loader. If there are no repositories, a zero-length array is returned.For security reason, returns a clone of the Array (since String are immutable).
Specified by:
findRepositories in interface Reloader


findResource

public URL findResource(String name)
Find the specified resource in our local repository, and return a URL refering to it, or null if this resource cannot be found.

Parameters:
name - Name of the resource to be found


findResourceInternal

protected ResourceEntry findResourceInternal(String name,
                                             String path)
Find specified resource in local repositories.

Returns:
the loaded resource, or null if the resource isn't found


findResources

public Enumeration findResources(String name)
            throws IOException
Return an enumeration of URLs representing all of the resources with the given name. If no resources with this name are found, return an empty enumeration.

Parameters:
name - Name of the resources to be found


getDebug

public int getDebug()
Return the debugging detail level for this component.


getDelegate

public boolean getDelegate()
Return the "delegate first" flag for this class loader.


getJarPath

public String getJarPath()
Return the JAR path.


getPermissions

protected PermissionCollection getPermissions(CodeSource codeSource)
Get the Permissions for a CodeSource. If this instance of WebappClassLoader is for a web application context, add read FilePermission or JndiPermissions for the base directory (if unpacked), the context URL, and jar file resources.

Parameters:
codeSource - where the code was loaded from

Returns:
PermissionCollection for CodeSource


getResource

public URL getResource(String name)
Find the resource with the given name. A resource is some data (images, audio, text, etc.) that can be accessed by class code in a way that is independent of the location of the code. The name of a resource is a "/"-separated path name that identifies the resource. If the resource cannot be found, return null.

This method searches according to the following algorithm, returning as soon as it finds the appropriate URL. If the resource cannot be found, returns null.

  • If the delegate property is set to true, call the getResource() method of the parent class loader, if any.
  • Call findResource() to find this resource in our locally defined repositories.
  • Call the getResource() method of the parent class loader, if any.

Parameters:
name - Name of the resource to return a URL for


getResourceAsStream

public InputStream getResourceAsStream(String name)
Find the resource with the given name, and return an input stream that can be used for reading it. The search order is as described for getResource(), after checking to see if the resource data has been previously cached. If the resource cannot be found, return null.

Parameters:
name - Name of the resource to return an input stream for


getResources

public DirContext getResources()
Get associated resources.


getURI

protected URL getURI(File file)
            throws MalformedURLException
Get URL.


getURL

protected URL getURL(File file)
            throws MalformedURLException
Get URL.


getURLs

public URL[] getURLs()
Returns the search path of URLs for loading classes and resources. This includes the original list of URLs specified to the constructor, along with any URLs subsequently appended by the addURL() method.

Returns:
the search path of URLs for loading classes and resources.


isPackageSealed

protected boolean isPackageSealed(String name,
                                  Manifest man)
Returns true if the specified package name is sealed according to the given manifest.


loadClass

public Class loadClass(String name)
            throws ClassNotFoundException
Load the class with the specified name. This method searches for classes in the same manner as loadClass(String, boolean) with false as the second argument.

Parameters:
name - Name of the class to be loaded


loadClass

public Class loadClass(String name,
                       boolean resolve)
            throws ClassNotFoundException
Load the class with the specified name, searching using the following algorithm until it finds and returns the class. If the class cannot be found, returns ClassNotFoundException.
  • Call findLoadedClass(String) to check if the class has already been loaded. If it has, the same Class object is returned.
  • If the delegate property is set to true, call the loadClass() method of the parent class loader, if any.
  • Call findClass() to find this class in our locally defined repositories.
  • Call the loadClass() method of our parent class loader, if any.
If the class was found using the above steps, and the resolve flag is true, this method will then call resolveClass(Class) on the resulting Class object.

Parameters:
name - Name of the class to be loaded
resolve - If true then resolve the class


modified

public boolean modified()
Have one or more classes or resources been modified so that a reload is appropriate?
Specified by:
modified in interface Reloader


openJARs

protected void openJARs()
Used to periodically signal to the classloader to release JAR resources.


refreshPolicy

protected void refreshPolicy()
Refresh the system policy file, to pick up eventual changes.


removeLifecycleListener

public void removeLifecycleListener(LifecycleListener listener)
Remove a lifecycle event listener from this component.
Specified by:
removeLifecycleListener in interface Lifecycle

Parameters:
listener - The listener to remove


setDebug

public void setDebug(int debug)
Set the debugging detail level for this component.

Parameters:
debug - The new debugging detail level


setDelegate

public void setDelegate(boolean delegate)
Set the "delegate first" flag for this class loader.

Parameters:
delegate - The new "delegate first" flag


setJarPath

public void setJarPath(String jarPath)
Change the Jar path.


setResources

public void setResources(DirContext resources)
Set associated resources.


setWorkDir

public void setWorkDir(File workDir)
Change the work directory.


start

public void start()
            throws LifecycleException
Start the class loader.
Specified by:
start in interface Lifecycle

Throws:
LifecycleException - if a lifecycle error occurs


stop

public void stop()
            throws LifecycleException
Stop the class loader.
Specified by:
stop in interface Lifecycle

Throws:
LifecycleException - if a lifecycle error occurs


toString

public String toString()
Render a String representation of this object.


validate

protected boolean validate(String name)
Validate a classname. As per SRV.9.7.2, we must restict loading of classes from J2SE (java.*) and classes of the servlet API (javax.servlet.*). That should enhance robustness and prevent a number of user error (where an older version of servlet.jar would be present in /WEB-INF/lib).

Parameters:
name - class name

Returns:
true if the name is valid


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