[移动开发]文件持久化

引入 pom.xml 依赖：

<dependency>
	<groupId>com.dyuproject.protostuff</groupId>
	<artifactId>protostuff-api</artifactId>
	<version>1.0.10</version>
</dependency>
<dependency>
	<groupId>com.dyuproject.protostuff</groupId>
	<artifactId>protostuff-core</artifactId>
	<version>1.0.10</version>
</dependency>

工具类：

/**
 * file 持久化、反持久化
 *
 */
public class PersistentUtil
{
    /**
     * 持久化到文件
     * @param filepath 文件路径格式：<b>"./fold1/fold2/data.txt"</b>
     * @param obj 对象
     * @param <T>
     * @throws IOException
     */
    public static <T> void save(String filepath, T obj) throws IOException
    {
        byte[] serializer = ProtostuffUtil.serializer(obj);
        ByteBuffer byteBuffer = ByteBuffer.wrap(serializer);
        write(filepath, byteBuffer);
    }

    /**
     * 反持久化到内存
     * @param filepath 文件路径
     * @param clazz 对象类型
     * @param <T>
     * @return
     * @throws IOException
     */
    public static <T> T load(String filepath, Class<T> clazz) throws IOException
    {
        ByteBuffer byteBuffer = read(filepath);
        byte[] bytes = byteBuffer.array();
        return ProtostuffUtil.deserializer(bytes, clazz);
    }

    /**
     * 读文件
     * @param filepath 文件路径
     * @return
     * @throws IOException
     */
    private static ByteBuffer read(String filepath) throws IOException
    {
        try (FileInputStream fis = new FileInputStream(filepath);
             FileChannel channel = fis.getChannel();)
        {
            // 一次性加载到内存才能反序列化
            ByteBuffer buffer = ByteBuffer.allocate((int) channel.size());
            channel.read(buffer);
            buffer.rewind();

            return buffer;
        }
    }

    /**
     * 写文件
     * @param filepath
     * @param buffer
     * @throws IOException
     */
    private static void write(String filepath, ByteBuffer buffer) throws IOException
    {
        createFile(filepath);

        try (FileOutputStream fos = new FileOutputStream(filepath);
             FileChannel channel = fos.getChannel();)
        {
            channel.write(buffer);
        }
    }

    /**
     * 创建文件
     * @param filepath 文件路径格式：<b>"./fold1/fold2/data.txt"</b>
     * @return
     * @throws IOException
     */
    private static File createFile(String filepath) throws IOException
    {
        File file = new File(filepath);
        if (!file.exists())
        {
            // 先创建父路径
            file.getParentFile().mkdirs();

            // 再创建子文件
            file.createNewFile();
        }

        return file;
    }

}

测试用例：

public static void main(String[] args) throws Exception
{
    // 持久化到本地磁盘
    String s = "is a good day!";
    PersistentUtil.save("./test/test.txt", s);

    // 反持久化到内存
    String ss = PersistentUtil.load("./test/test.txt", String.class);
    System.out.println(ss);
}