Mega Code Archive
The class that implements a simple LRU cache
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/*
* Copyright 2008 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
*
* 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 org.dopdf.utils;
import java.util.LinkedHashMap;
import java.util.Map;
/**
* The class that implements a simple LRU cache.
*
* @param <K> the type of key that will be held by this LRU cache.
* @param <V> the type of value held by this LRU cache.
* @author Deep Shah
*/
public class LRUCache<K, V> {
/** The backing linked hash map object that will implement the LRU algorithm for us. */
private static final LinkedHashMap cache = new LinkedHashMap(Constants.Cache.MAX_CAPACITY,
Constants.Cache.LOAD_FACTOR, true) {
/**
* {@inheritDoc}
*/
@Override
protected boolean removeEldestEntry(final Map.Entry eldest) {
return size() > Constants.Cache.SIZE;
}
};
/**
* Puts the key value pair in the LinkedHashmap.
* @param key the key value to put in the map.
* @param value the value to put in the map.
*/
public void put(final K key, final V value) {
cache.put(key, value);
}
/**
* The method that gets the value from the LRU cache for the given key. If the value is not found null is returned.
* @param key the key for which we have to find the value in the cache.
* @return The value matching the passed in key. Null if no match is found.
*/
public V get(final K key) {
return (V) cache.get(key);
}
/**
* The method that returns true if the cache holds the given key.
* @param key the key which we have to find in the cache.
* @return true if the value against the given key is found, false otherwise.
*/
public boolean containsKey(final K key) {
return cache.containsKey(key);
}
}
class Constants {
/**
* The class that holds constatns for the cache class
*
* @author Deep Shah
*/
public class Cache {
/**
* The load factor for the cache.
*/
public static final float LOAD_FACTOR = 0.75f;
/**
* The max size of the cahce.
*/
public static final int SIZE = 15;
/**
* The max capacity of the cahce.
*/
public static final int MAX_CAPACITY = ((int) (SIZE / LOAD_FACTOR) + 1);
}
/**
* The class that holds the constants for the resources.
*
* @author Deep Shah
*/
public class Resource {
/**
* The content type of jpeg images.
*/
public static final String JPEG_CONTENT_TYPE = "image/jpeg";
/**
* The content type of png images.
*/
public static final String PNG_CONTENT_TYPE = "image/png";
/**
* The content type of pdf document.
*/
public static final String PDF_CONTENT_TYPE = "application/pdf";
/**
* The constant that represents the jpeg format.
*/
public static final String JPEG_FORMAT = "jpeg";
/**
* The constant that represents the png format.
*/
public static final String PNG_FORMAT = "png";
/**
* Text plain content type.
*/
public static final String TEXT_CONTENT_TYPE = "text/plain";
/**
* The constant that represents the javascript format.
*/
public static final String JAVASCRIPT_FORMAT = "js";
/**
* The constant that represents the css format.
*/
public static final String CSS_FORMAT = "css";
/**
* The string pattern that identifies that the request is for a static resource.
*/
public static final String STATIC_RESOURCE_PATTERN = ".+/static/.+(js|css|png)$";
/**
* The string pattern that identifies the download request.
*/
public static final String DOWNLOAD_RESOURCE_PATTERN = ".+download/document*";
/**
* The pattern that identifies the pdf page request.
*/
public static final String PDF_PAGE_RESOURCE_PATTERN = ".+/page/show*";
}
/**
* The class that holds he PDFPage related constants.
*/
public class PDFPage {
/**
* The constant representing the id key.
*/
public static final String ID_KEY = "id";
/**
* The constant representing the strategy key.
*/
public static final String STRATEGY_KEY = "strategy";
/**
* The constant representing the Page key.
*/
public static final String PAGE_KEY = "page";
/**
* The size of the page to be rendered.
*/
public static final String SIZE_KEY = "size";
}
/**
* The constants for the DocumentHashingStrategy.
*
* @author Deep Shah
*/
public enum PDFFetchingStrategy {
/**
* The constant that represents the LRU strategy.
*/
LRU,
/**
* The constant that represents the SESSION strategy.
*/
SESSION;
/**
* The method that returns an instance of PDFFetchingStrategy based on the strategy name passed as argument.
*
* @param pdfFetchingStrategyName the name of the strategy to use. If null or empty is passed LRU will be returned.
* @return The reference of PDFFetchingStrategy that matches the name passed.
*/
public static PDFFetchingStrategy parse(final String pdfFetchingStrategyName) {
if (pdfFetchingStrategyName == null
|| pdfFetchingStrategyName.equals("")
|| pdfFetchingStrategyName.equalsIgnoreCase(Constants.General.UNDEFINED)) return LRU;
return valueOf(pdfFetchingStrategyName.toUpperCase());
}
}
/**
* The enum that holds various page sizes.
*
* @author Deep Shah
*/
public enum PageSize {
/**
* The small page size.
*/
SMALL(392, 554),
/**
* The medium page size.
*/
MEDIUM(617, 873),
/**
* The large page size.
*/
LARGE(853, 1207);
/**
* The width represented by this size.
*/
private int width;
/**
* The height represented by this size.
*/
private int height;
/**
* The constructor that takes in width and height as argument.
*
* @param width the width.
* @param height the height.
*/
private PageSize(final int width, final int height) {
this.width = width;
this.height = height;
}
/**
* The method that will return an instance of page size based on the string value of size passed.
* If null of empty string is passed medium will be returned.
*
* @param size the string value of size to use.
* @return the PageSize reference that matches the size passed in.
*/
public static PageSize parse(final String size) {
if (null == size || size.equals("") || size.equalsIgnoreCase(Constants.General.UNDEFINED)) return MEDIUM;
return valueOf(size.toUpperCase());
}
/**
* The getter for the width.
*
* @return the value held.
*/
public int getWidth() {
return width;
}
/**
* The getter for the height.
*
* @return the value held.
*/
public int getHeight() {
return height;
}
}
/**
* The class that holds information about the general constants.
*
* @author Deep Shah
*/
public class General {
/**
* The undefined value constant.
*/
public static final String UNDEFINED = "UNDEFINED";
}
}
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