In -depth discussion of "Disk Lru Cache" framework technical principles in the Java class library

Topic: In -depth discussing the technical principles of "Disk Lru Cache" framework in the Java class library Summary: With the advent of the digital age, the storage and access of data have become increasingly important.For data that requires frequent access, modification and deletion, cache is an effective technique to improve system performance.Among them, DISK LRU Cache framework technology is a cache implementation commonly used in modern software development.This article will in -depth discussions on the technical principles of the "Disk Lru Cache" framework in the Java class library to introduce its working principles and code configuration. I. Introduction 1.1 The background and significance of cache technology 1.2 Disk recently used (DISK LRU) cache introduction and advantage Second, frame principle 2.1 DISK LRU CACHE Framework Principles Overview 2.2 cache structure: lrucache 2.3 Data Storage: DiskLRUCACHE 2.4 Reading and writing process: DiskCache 3. Code configuration and examples 3.1 Environmental configuration and dependence 3.2 DISK LRU CACHE framework code use example 3.3 Configuration parameter introduction Fourth, expansion and optimization 4.1 performance optimization strategy of framework 4.2 Capacity configuration and expansion strategy 4.3 cache strategy and elimination algorithm 5. Summary Foreword: With the rapid development of the Internet, the load on the server is getting heavier. In order to improve the response speed of users, reduce the pressure of service, efficient data caching processing has become an important task.Caches is a commonly used method for improving service performance. It stores frequently read data in a faster medium, such as memory or disk to reduce access to databases or remote interfaces.In order to meet the needs of large -scale applications, the disk has recently emerged as the minimum (DISK LRU) cache technology. I. Introduction 1.1 The background and significance of cache technology In modern software development, the cost of accessing remote resources (such as networks) is significantly higher than access local resources, such as CPUs, memory and disks.The cache technology is stored in the local resources by stored the results of the request to reduce the needs of frequent access to remote resources, thereby improving the response speed and performance of the system. 1.2 Disk recently used (DISK LRU) cache introduction and advantage Disk LRU has recently used (DISK LRU) cache is a cache technology based on disk storage.Compared to traditional memory cache, disk cache has greater storage space, can store more data, and can save data persistently.The DISK LRU Cache framework provides an efficient data storage and access method that can automatically manage the capacity of cache and eliminate data that is no longer used according to the cache strategy. Second, frame principle 2.1 DISK LRU CACHE Framework Principles Overview The Disk Lru Cache framework implements the cache function through two main components: Lrucache and DiskLRUCACHE.Lrucache is used for memory cache and manages data in memory by achieving the recent minimum (LRU) algorithm.Disklrucache is used for disk cache, and the data is durable by storing the cache data in the file system. 2.2 cache structure: lrucache Lrucache is the core component used in the Disk Lru Cache framework for memory cache.It stores data storage and access by using a two -way linked list and a hash table.Whenever the data in the cache, Lrucache moves the data to the head of the linked list to indicate that the data is recently visited.When the cache capacity reaches the upper limit of the default, Lrucache removes the minimum data used from the rear of the linked list. 2.3 Data Storage: DiskLRUCACHE Disklrucache is a component for disk cache in the Disk Lru Cache framework.It saves the cache data in the file in the file system to achieve the durable data.Disklrucache uses the hash algorithm to map different cache keys to different files, and to achieve data storage and access through file reading and writing operations.Disklrucache also provides some advanced features, such as data expired strategies, data compression and encryption. 2.4 Reading and writing process: DiskCache DiskCache is an interface used to read and write cache in the Disk Lru Cache framework.It defines the operation method of reading and writing cache data.When reading data from the cache, Diskcache first tries to read data from Lrucache. If not found, read from DiskLRUCACHE.When the data is written to the cache, DiskCache will first write the data into Lrucache, and then write it to the files in DiskLrucache. 3. Code configuration and examples 3.1 Environmental configuration and dependence Before using the Disk Lru Cache framework, you need to configure related dependencies and environments.First of all, you need to add references to the DISK LRU Cache library in the construction file of the project, such as Gradle dependencies or Maven dependencies.Then, before using the library, you need to initialize and configure parameters in the code, such as cache capacity, cache path, etc. 3.2 DISK LRU CACHE framework code use example Here are a simple example code to demonstrate how to use the Disk Lru Cache framework to achieve data cache. // Initialize disklrucache DiskLruCache diskCache = DiskLruCache.open(cacheDir, appVersion, valueCount, maxSize); // Initialize lrucache LruCache<String, Bitmap> memoryCache = new LruCache<>(maxSize); // Read data from the cache public Bitmap get(String key) { // Read from the memory cache first Bitmap bitmap = memoryCache.get(key); if (bitmap != null) { return bitmap; } // Read from the disk cache String diskKey = hashKeyForDisk(key); DiskLruCache.Snapshot snapshot = diskCache.get(diskKey); if (snapshot != null) { InputStream inputStream = snapshot.getInputStream(0); bitmap = BitmapFactory.decodeStream(inputStream); inputStream.close(); // Put the data into the memory cache memoryCache.put(key, bitmap); } return bitmap; } // Write the data into the cache public void put(String key, Bitmap bitmap) { // Write a memory cache memoryCache.put(key, bitmap); // Write into the disk cache String diskKey = hashKeyForDisk(key); DiskLruCache.Editor editor = diskCache.edit(diskKey); if (editor != null) { OutputStream outputStream = editor.newOutputStream(0); bitmap.compress(Bitmap.CompressFormat.JPEG, 100, outputStream); outputStream.close(); editor.commit(); } } // Delete the cache data public void remove(String key) { memoryCache.remove(key); String diskKey = hashKeyForDisk(key); diskCache.remove(diskKey); } // Calculate the hash value of the cache key private String hashKeyForDisk(String key) { try { final MessageDigest md = MessageDigest.getInstance("MD5"); md.update(key.getBytes()); return bytesToHexString(md.digest()); } catch (NoSuchAlgorithmException e) { return String.valueOf(key.hashCode()); } } // Byte -to -hexisted strings private String bytesToHexString(byte[] bytes) { StringBuilder sb = new StringBuilder(); for (byte b : bytes) { String hex = Integer.toHexString(0xFF & b); if (hex.length() == 1) { sb.append('0'); } sb.append(hex); } return sb.toString(); } 3.3 Configuration parameter introduction When using the Disk Lru Cache framework, you can configure related parameters according to actual needs, such as cache capacity, cache path, etc. -Cachedir: Storage path of cache file. -PPVERSION: Edition number of the application. -ValueCount: The number of files corresponding to each cache key. -MaxSize: Maximum capacity of memory cache. Fourth, expansion and optimization 4.1 performance optimization strategy of framework In order to improve the performance of the framework, some optimization strategies can be adopted, such as pre -load, asynchronous reading and writing, and data compression.Pre -load can be pre -loaded in the cache when the application starts to improve the user experience.Asynchronous reading and writing can avoid blocking the main thread and improve the response speed.Data compression can reduce the occupation of disk space and improve storage efficiency. 4.2 Capacity configuration and expansion strategy When using the framework, the cache capacity and extension strategy can be configured according to the actual needs.The maximum capacity of memory cache and disk cache can be set to avoid data with too much cache.For lack of capacity, a certain elimination strategy can be adopted, such as deleting the oldest data or elimination according to the frequency of access. 4.3 cache strategy and elimination algorithm In order to improve the effectiveness of the cache data, the corresponding cache strategy and elimination algorithm can be developed.You can formulate a reasonable cache strategy according to factors such as the life cycle and access frequency of the data, such as advanced first -out (FIFO) or the recent minimum use (LRU).The elimination algorithm can be comprehensively considered according to factors such as access, access time, and data, and try to retain the most valuable data as much as possible. 5. Summary This article deeply explores the "Disk Lru Cache" framework technical principle in the Java class library.By analyzing the working principle and code example of the framework, the data structure and reading and writing process of Disk Lru Cache are understood.At the same time, some configuration parameters and extended optimization strategies are provided to help developers better understand and apply the framework to improve system performance and user experience.