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JGDMS Preferred RMIClassLoader Providers
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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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
*
* http://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 net.jini.loader.pref;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.HashMap;
import java.util.Map;
import java.util.Iterator;
import java.util.TreeSet;
/**
* Internal data structure which holds preference information for a
* preferred class loader. This utility is used only by the preferred
* class loader provider and is not intended to be a public API.
*
* A preferred resources object is created from an input stream which
* is formatted according to the Preferred List Syntax which is
* defined in the specification for
* net.jini.loader.pref.PreferredClassProvider
*
* Preferred resources instances hold preferred list expression data
* and the preferred state for the resources contained in a given
* preferred class loader.
*
* PreferredResouces is thread safe.
* Originally from package org.apache.river.loader.pref.internal.
*
* @author Sun Microsystems, Inc.
* @since 2.0
*/
final class PreferredResources {
/**
* Constant value that indicates that there is no preference value
* for a given name.
*/
public static final int NAME_NO_PREFERENCE = 0;
/**
* Constant value that indicates that the resource for a given
* name is known to be not preferred. This state is applicable
* when a preference expression declared that the name is not
* preferred or when the resource for the name (preferred or not)
* is known to not exist.
*/
public static final int NAME_NOT_PREFERRED = 1;
/**
* Constant value that indicates that a given name is preferred.
* This state is applicable when a preference expression declares
* the name to be preferred but it is uncertain whether the
* resource for the name the exists.
*/
public static final int NAME_PREFERRED = 2;
/**
* Constant value that indicates that a given resource is
* preferred. This state is applicable when a preference
* expression declares the name to be preferred and the resource
* for the name is known to exist.
*/
public static final int NAME_PREFERRED_RESOURCE_EXISTS = 3;
/** string that starts preference specification headers */
private static final String HEADER_TITLE = "PreferredResources-Version: ";
private static final String HEADER_MAJOR_VERSION = "1";
private static final String HEADER_MINOR_VERSION = "0";
/** preference syntax keywords */
private static final String PREF_PREFIX = "Preferred:";
private static final String NAME_PREFIX = "Name:";
/* tables which contain relevant components of preferred names */
private final Map namespacePrefs;
private final Map packagePrefs;
private final Map completeNamePrefs;
/** flag to signal if this preference object is empty */
private volatile boolean isEmpty = true;
/** default preference setting */
private final Boolean defaultPreference;
/**
* Create a preference object from a stream of formatted
* preference syntax.
*
* @see PreferredResources
*/
public PreferredResources(InputStream in) throws IOException {
/*
* Read and parse preference information from the parameter input
* stream in. When complete, the
* preference expression maps contain preference settings for
* preference names contained in the input stream.
*/
BufferedReader br = new BufferedReader
(new InputStreamReader(in, "UTF8"));
String line;
String name = null;
Boolean preference = null;
Boolean defaultPreference = Boolean.FALSE;
completeNamePrefs = new HashMap(53);
packagePrefs = new HashMap(23);
namespacePrefs = new HashMap(11);
if ((line = readLineTrimComments(br)) != null) {
if (!line.startsWith(HEADER_TITLE)) {
throw new IOException("unsupported preferred list header: " +
line);
} else {
String version =
line.substring(HEADER_TITLE.length(),
line.length()).trim();
if (!version.startsWith("1.")) {
throw new IOException("preferred list major version " +
"not supported");
}
}
for (line = readLineTrimComments(br); line != null;
line = readLineTrimComments(br))
{
if (line.length() == 0) {
continue;
} else if (line.startsWith(NAME_PREFIX)) {
if (name != null) {
throw new IOException("Preferred name without " +
"preference value");
}
name = line.substring(NAME_PREFIX.length()).trim();
continue;
} else if (line.startsWith(PREF_PREFIX)) {
String value = line.substring(PREF_PREFIX.length()).trim();
if (value.equals("")) {
throw new IOException("Empty preference value not " +
"permitted");
}
preference = Boolean.valueOf(value);
} else {
throw new IOException("unrecognized preference entry: " +
line);
}
if (name == null) {
if (preference != null) {
if (!isEmpty) {
throw new IOException("default preference must " +
"be the first expression and can not " +
"be redefined");
}
defaultPreference = preference;
preference = null;
isEmpty = false;
}
/* it is ok for both name and preference to be null */
} else if (preference != null) {
if (name.startsWith("/") ||
name.startsWith("*") ||
name.startsWith("-") ||
name.startsWith("."))
{
throw new IOException("Invalid character " +
"at name beginning: " + name);
} else if (name.endsWith("/*")) {
mapPut(packagePrefs,
name.substring(0, name.length() - 2), preference);
} else if (name.endsWith("/-")) {
mapPut(namespacePrefs,
name.substring(0, name.length() - 2), preference);
} else if (name.endsWith("/")) {
mapPut(packagePrefs,
name.substring(0, name.length() - 1), preference);
} else {
/* no wildcard; must be a full resource name */
int state = (preference.booleanValue() ?
NAME_PREFERRED : NAME_NOT_PREFERRED);
mapPut(completeNamePrefs, name, Integer.valueOf(state));
}
preference = null;
name = null;
}
}
if (name != null) {
throw new IOException("Preferred name without " +
"preference value");
}
}
if (isEmpty) {
throw new IOException("Empty preferences list is invalid");
}
this.defaultPreference = defaultPreference;
}
/**
* Reads the next line from the specified BufferedReader, removing
* leading and trailing whitespace and comments. Null is returned
* on EOF.
**/
private String readLineTrimComments(BufferedReader br) throws IOException {
String line = br.readLine();
if (line != null) {
line = line.trim();
if (line.indexOf('#') == 0) {
line = "";
}
}
return line;
}
/**
* Insert a preference expression and value into a given map.
*/
private void mapPut(Map map, String name, Object preference)
throws IOException
{
isEmpty = false;
if ((name == null) || (name.length() == 0)) {
throw new IOException("no name specified in preference" +
" expression");
}
if (map.put(name, preference) != null) {
throw new IOException("duplicate map entry: " + name);
}
}
/**
* Write the preferences to the specified OutputStream using the
* preference list syntax. Preference expressions are written in
* the following order:
*
* Complete name expressions
*
* Package expressions
*
* Namespace expressions
*
* @param out the stream to which formatted preference information
* will be written
* @throws IOException if an error occurs while writing to the stream
*/
public void write(OutputStream out) throws IOException {
BufferedWriter bw = new BufferedWriter
(new OutputStreamWriter(out, "UTF8"));
/* write the specification header */
bw.write(HEADER_TITLE + "1.0\n");
bw.write(PREF_PREFIX + " " + defaultPreference + "\n\n");
/* write out most specific preferences first */
synchronized (completeNamePrefs){
writeMap(completeNamePrefs, bw, "");
}
synchronized (packagePrefs){
writeMap(packagePrefs, bw, "/*");
}
synchronized (namespacePrefs){
writeMap(namespacePrefs, bw, "/-");
}
bw.flush();
}
/**
* Write the contents of the map into out using the
* preference syntax.
*/
private void writeMap(Map prefs, Writer out, String suffix)
throws IOException
{
Iterator i = (new TreeSet(prefs.keySet())).iterator();
while (i.hasNext()) {
String current = i.next();
out.write(NAME_PREFIX + " " + current +
suffix + "\n");
Object value = prefs.get(current);
if (value instanceof Boolean) {
out.write(PREF_PREFIX + " " + value + "\n\n");
} else if (value instanceof Integer) {
int state = ((Integer) value).intValue();
if ((state == NAME_PREFERRED) ||
(state == NAME_PREFERRED_RESOURCE_EXISTS))
{
out.write(PREF_PREFIX + " " + true + "\n\n");
} else {
out.write(PREF_PREFIX + " " + false + "\n\n");
}
}
}
}
/**
* Returns the preference setting that will be applied to names
* which have no explicit preference setting in contained
* preference settings. The default preference is set by the
* first preference setting with no associated name in a
* preferences list file.
*
* @return default boolean preference value for these preferences
*/
public Boolean getDefaultPreference() {
return defaultPreference;
}
/**
* Enable MarshalInputStream to optimize preference information:
* permits complete name expressions to be added for names that
* only match wild-card expressions. These added expressions hold
* data that tells if a resource has been loaded.
*
* This method makes this object mutable. Synchronization must be
* used to ensure consistent preference state when this method is
* called.
*
* @param name the name for which preferred state will be set
* @param prefState the preferred state for the given name
* @throws IOException if the name length is zero length
*/
public void setNameState(String name, int prefState)
throws IOException
{
isEmpty = false;
if (name.length() == 0) {
throw new IOException("no name specified in preference" +
" expression");
}
synchronized (completeNamePrefs){
completeNamePrefs.put(name, Integer.valueOf(prefState));
}
}
/**
* Searches the preference maps to determine the preference state
* of the named resource. The preference state for the given
* resource name is returned. The preference state is an integer
* that is equal to one of the preference state values defined
* above. This state integer tells the preference value of name
* and whether its resource is known to exist.
*
* @param name
* @param isClass whether the given name refers to a
* class resource
*
* @return the state for the given name which will be set to one
* of the following values: NAME_NO_PREFERENCE,
* NAME_NOT_PREFERRED, NAME_PREFERRED,
* NAME_PREFERRED_RESOURCE_EXISTS
*
* @throws IOException if an error occurs getting the state for
* the supplied name
*/
public int getNameState(String name, boolean isClass)
throws IOException
{
Integer state;
if (isClass) {
state = getClassNameState(name);
} else {
synchronized (completeNamePrefs){
state = (Integer) completeNamePrefs.get(name);
}
}
if (state != null) {
return state.intValue();
}
return NAME_NO_PREFERENCE;
}
/**
* Returns the preference state for a given name (as is done in
* getNonclassNameState) but also interprets the notation for
* inner classes as a wild card so that the preference value for a
* container class propagates to the classes it contains. More
* specific inner classes names override more general container
* preference.
*/
private Integer getClassNameState(String name) throws IOException {
if (!name.endsWith(".class")) {
throw new IOException("requested name state on a " +
"non-class resource: " + name);
}
Integer state = null;
String container = name;
int lastDollar = -1;
synchronized(completeNamePrefs){
do {
state = (Integer) completeNamePrefs.get(container);
if (state == null) {
lastDollar = container.lastIndexOf("$");
if (lastDollar >= 0) {
container =
container.substring(0, lastDollar) + ".class";
}
}
} while ((lastDollar >= 0) && (state == null));
}
return state;
}
/**
* Return the boolean value of the most specific wild card
* (package and namespace) expression which matches
* name. Package preferences are always more
* specific than namespace preferences.
*
* @param name the resource name to which the returned boolean
* value will apply
*
* @return Boolean.TRUE if name is
* preferred. Boolean.FALSE is it is
* not. null if there is no wildcard preference for
* the name.
*/
public Boolean getWildcardPreference(String name) {
Boolean wildcardPref = null;
int lastSlash = name.lastIndexOf("/");
if (lastSlash >= 0) {
String mostSpecific = name.substring(0, lastSlash);
if (!mostSpecific.equals("")) {
synchronized (packagePrefs){
if (!packagePrefs.isEmpty()) {
wildcardPref = (Boolean)
packagePrefs.get(mostSpecific);
}
}
if (wildcardPref == null) {
wildcardPref = getNamespacePreference(mostSpecific);
}
}
}
return wildcardPref;
}
/**
* Return a Boolean for the most specific namespace expression
* which matches name. null if the name does not
* match a namespace preference expression.
*/
private Boolean getNamespacePreference(String namespace) {
Boolean namespacePref = null;
synchronized (namespacePrefs){
if (!namespacePrefs.isEmpty()) {
int lastSlash;
do {
namespacePref =
(Boolean) namespacePrefs.get(namespace);
lastSlash = namespace.lastIndexOf("/");
if (lastSlash >= 0) {
namespace = namespace.substring(0, lastSlash);
}
} while ((lastSlash >= 0) &&
(!namespace.equals("")) &&
namespacePref == null);
}
}
return namespacePref;
}
}
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