缓存对象到文件和从文件获取对象

冷不防 2023-03-01 12:30 52阅读 0赞

### 背景 ###

我们在工作中可能会遇到这样的场景，我们需要定时获取获取一个对象。但这个对象比较大，数量比较多。缓存在redis，数据库里面都不太合适。这个时候我们可以考虑将文件缓存本地文件当中。

### 代码 ###

1、配置文件文件缓存路径  
在application.properties中添加

fileCacheDir=C:\\Users\\Administrator\\Desktop\\deploy

2、设置文件缓存路径

@Configuration
    public class FileCacheConfig {
    
        @Value("${fileCacheDir}")
        private String fileCacheDir;
    
    
        @Bean
        public FileCache getFileCache(){
           return new FileCache(fileCacheDir);
        }
    }

3、操作文件缓存对象

接口

public interface ICache {
        /**
         * 根据key获取缓存数据
         * @param key  存储key
         * @return 缓存到文件中的数据
         */
        <T> T get(String key) throws IOException, ClassNotFoundException, Exception;
    
        /**
         * 添加缓存
         *   @param key  存储key
         * @param data 缓存到文件中的数据
         */
        int set(String key, Object data) throws IOException;
    
    
        /**
         * 删除
         *  @return 删除影响的行数
         */
        int delete(String key);
    }

具体操作类：

public class FileCache implements ICache {
    
        private String cacheDir;
    
        public FileCache(String cacheDir) {
            this.cacheDir = cacheDir;
        }
    
        @Override
        public Object get(String key) throws Exception {
            File file = new File(this.getRealFilePath(key));
            if (!file.exists()) {
                return null;
            }
            //获取文件中对象
            Object fileObject = FileOperate.getFileObject(file);
            Object fileStorageObject = null;
            if ( fileObject instanceof FileCacheObject) {
                FileCacheObject fcObject = (FileCacheObject)fileObject;
                //查看缓存是否过期
                if (!fcObject.isCacheExpire()) {
                    fileStorageObject = fcObject.getStorageObject();
                }
            }
    
            //如果不存在活已经过期就删除
            if (null == fileStorageObject) {
                file.delete();
            }
            return fileStorageObject;
        }
    
        @Override
        public int set(String key, Object data) throws IOException {
            String filePath = this.getRealFilePath(key);
            return FileOperate.saveObjectToFile(filePath, new FileCacheObject(data)) ? 1 : 0;
    
        }
    
        @Override
        public int delete(String key) {
            String filePath = this.getRealFilePath(key);
            File file = new File(filePath);
            if (!file.exists()) {
                return 1;
            }else {
                return file.delete() ? 1 : 0;
            }
    
        }
    
        /**
         * 获取cache 所存的文件相对路径
         * @param cacheId 缓存id
         */
        protected String getRealFilePath(String cacheId) {
            StringBuilder sb = new StringBuilder(cacheDir);
            if (!cacheDir.endsWith(File.separator)) {
                sb.append(File.separator);
            }
            cacheId = cacheId.toLowerCase();
            sb.append(DigestUtils.md5DigestAsHex(cacheId.getBytes()));
            return sb.toString();
        }
    }

4、对接文件和对象转化文件操作类

public class FileOperate {
    
        public final static String DEFAULT_ENCODING = "UTF-8";
    
        /**
         * 获取文件路径对应文件对象
         */
        public static Object getFileObject(String filePath) throws IOException, ClassNotFoundException {
            return getFileObject(new File(filePath));
        }
    
    
        /**
         * 读取文件中的对象
         */
        public static Object getFileObject(File file) throws IOException, ClassNotFoundException {
            if (!file.exists()) {
                return null;
            }
            try(ObjectInputStream ois=new ObjectInputStream(new FileInputStream(file))){
                return ois.readObject();
            }
    
        }
    
        /**
         * 读取文件路劲对应文件的内容
         * @param filePath 文件路径
         * @param encoding 编码格式
         * @return  文件对象
         */
        public static String getFileContent(String filePath,String encoding) throws IOException {
            return getFileContent(new File(filePath), encoding);
        }
    
    
        /**
         * 读取文件的文本内容
         */
        public static String getFileContent(File file,String encoding) throws IOException {
            if (!file.exists()) {
                return null;
            }
    
            try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(file));
                 ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
    
                encoding = StringUtils.isEmpty(encoding) ? DEFAULT_ENCODING : encoding;
                int readLen;
                byte[] data = new byte[4096];
                while ((readLen = bis.read(data)) != -1) {
                    baos.write(data, 0, readLen);
                }
                return baos.toString(encoding);
    
            }
        }
    
        /**
         * 读取文件大小
         */
        public static long getFileLength(File file) throws IOException {
            if (!file.exists()) {
                return 0;
            }
            long total = 0;
            try(FileInputStream fis=new FileInputStream(file)){
    
                while (true) {
                    int expect = fis.available();
                    if (expect < 0) {
                        break;
                    }
                    skip(fis,expect);
                    total += expect;
                }
            }
            return total;
        }
    
        public static void skip(FileInputStream fis, long expect) throws IOException {
            int maxTryTime = 16;
            while (expect > 0 && maxTryTime-- > 0) {
                long current = fis.skip(expect);
                if (current == expect) {
                    return;
                }else {
                    expect -= current;
                }
    
            }
        }
    
    
        /**
         * 保存内荣到文件
         */
        public static boolean saveContentToFile(String filePath, String content) throws IOException {
            return saveContentToFile(filePath, content, null);
        }
    
        /**
         * 保存内荣到文件
         */
        public static boolean saveContentToFile(String filePath, String content,String encoding) throws IOException {
            if (StringUtils.isEmpty(encoding)) {
                encoding = DEFAULT_ENCODING;
            }
            return saveContentToFile(filePath, content.getBytes(encoding));
        }
    
        /**
         * 保存内容到文件
         */
        public static boolean saveContentToFile(String filePath, byte[] data) throws IOException {
            if(!FileOperate.createDir(filePath,true)){
                return false;
            }
    
            try (FileOutputStream fos = new FileOutputStream(filePath)) {
                fos.write(data);
                fos.flush();
                return true;
            }
        }
    
    
        /**
         * 保存对象到文件中
         */
        public static boolean saveObjectToFile(String filePath, Object obj) throws IOException {
            if(!FileOperate.createDir(filePath,true)){
                return false;
            }
            try (ObjectOutputStream oos=new ObjectOutputStream(new FileOutputStream(filePath))){
                oos.writeObject(obj);
                oos.flush();
                return true;
            }
        }
    
        /**
         * 创建目录
         */
        public static boolean createDir(String path, boolean isFile) {
            File file = new File(path);
            if (isFile) {
                file = file.getParentFile();
            }
    
            if (!file.exists()) {
                return file.mkdirs();
            }else {
                return true;
            }
    
        }
    }

5、缓存对象类

@Data
    public class FileCacheObject  implements Serializable {
        private static final long serialVersionUID = 908523022948306952L;
    
        private long createTime;
    
        private long timeout;
    
        private Object storageObject;
    
        public FileCacheObject() {
        }
    
        public FileCacheObject(Object storageObject) {
            this(Integer.MAX_VALUE, storageObject);
        }
    
        public FileCacheObject(long timeout, Object storageObject) {
            if (!(storageObject instanceof Serializable)) {
                throw new IllegalArgumentException("storage object must implement Serializable");
            }
            this.createTime = System.currentTimeMillis();
            this.timeout = timeout;
            this.storageObject = storageObject;
        }
    
        /**
         * 缓存是否过期
         * @return 缓存存是否过期
         */
        public boolean isCacheExpire(){
            //等于0 表示无过期时间
            if (timeout == 0) {
                return false;
            }
            return createTime + timeout < System.currentTimeMillis();
        }
    
    
    }

7、测试类

@RunWith(SpringRunner.class)
    @SpringBootTest
    public class FileCacheTest {
    
        @Resource
        private FileCache fileCache;
    
        private static final String FILE_CACHE_KEY = "file_cache_key";
    
        @Test
       public void loadData() throws Exception {
           List<User> users = new ArrayList<>();
           User user1 = User.builder().id(1L).accountBalance(1L).email("email1").headPic("pic1").build();
           User user12 = User.builder().id(2L).accountBalance(2L).email("email2").headPic("pic2").build();
           users.add(user1);
           users.add(user12);
           fileCache.set(FILE_CACHE_KEY, users);
    
           List userList2= (List<User>)fileCache.get(FILE_CACHE_KEY);
           System.out.println(userList2);
    
       }
    }

打印的具体结果  
![在这里插入图片描述][20200725155042927.png]  
缓存在本地文件  
![在这里插入图片描述][20200725155110637.png]

附上User类：

@Data
    @Builder
    @NoArgsConstructor
    @AllArgsConstructor
    public class User implements Serializable {
    
        private Long id;
    
        private String username;
    
        private String password;
    
        private String phone;
    
        private String email;
    
        private Date created;
    
        private Date updated;
    
        private String sourceType;
    
        private String nickName;
    
        private String name;
    
        private String status;
    
        private String headPic;
    
        private String qq;
    
        private Long accountBalance;
    
        private String isMobileCheck;
    
        private String isEmailCheck;
    
        private String sex;
    
        private Integer userLevel;
    
        private Integer points;
    
        private Integer experienceValue;
    
        private Date birthday;
    
        private Date lastLoginTime;
    
    }

[20200725155042927.png]: /images/20230208/1a8a5a1657464bc6b7129563fe9ad194.png
[20200725155110637.png]: /images/20230208/95f6095b57d04e0e9bba2e87c3267549.png