RelaTable Storage

Java library for RDBMS-based file storage with compression and encryption support

• Files are always stored internally in ZIP format in order to get CRC-32 check, compression and AES encryption for free.
  • The compression level is customizable from NONE to HIGH.
  • Compression and encryption are transparent to the client, so no manual unzip is needed.
  • The CONTENT_LENGTH value represents the original uncompressed size of the object, it is NOT the BLOB length.
• This store has a flat structure instead of a hierarchy, so there is no native support for things like directories or folders, however common file name prefixes (like foo/, bar/) can be used to organize objects simulating a hierarchical structure. For more info, please check the Amazon S3 documentation because the semantics are similar.
• This library requires JDK 11 and depends on the Spring Framework but no Spring Context is actually needed (see the sample Java code below).

FILENAME	CONTENT_LENGTH	LAST_MODIFIED	COMPRESSED	ENCRYPTED	FILE_CONTENTS	UUID_BASE64URL	CREATION_TIME
foo.txt	123	2022-10-31 23:10:22,607	1	0	(BLOB)	IKn6ATU7RVa-qbykef7BfQ	2022-10-31 23:10:22,610
bar.png	4567	2022-10-31 23:10:49,669	0	0	(BLOB)	2WGTuBeQTu-iS5pUccAASQ	2022-10-31 23:10:49,672
baz.zip	89012	2022-10-31 23:11:02,607	0	1	(BLOB)	S2LzZ8f5S_6e5fT_p5N0Hw	2022-10-31 23:11:02,610

Usage

Add the Maven dependency

<dependency>
    <groupId>io.github.albertus82.storage</groupId>
    <artifactId>relatable-storage</artifactId>
    <version>0.2.0</version>
</dependency>

Create the database table

CREATE TABLE storage (
    uuid_base64url   VARCHAR(22 /* BYTE */) NOT NULL PRIMARY KEY,
    filename         VARCHAR(1024 /* CHAR */) NOT NULL UNIQUE,
    content_length   NUMERIC(19, 0) /* NOT NULL DEFERRABLE INITIALLY DEFERRED */ CHECK (content_length >= 0),
    last_modified    TIMESTAMP NOT NULL,
    compressed       NUMERIC(1, 0) NOT NULL CHECK (compressed IN (0, 1)),
    encrypted        NUMERIC(1, 0) NOT NULL CHECK (encrypted IN (0, 1)),
    file_contents    BLOB NOT NULL,
    creation_time    TIMESTAMP DEFAULT CURRENT_TIMESTAMP NOT NULL
);

When not using encrypion, you can also enable BLOB deduplication, if supported by your DBMS.

Sample Java code

DataSource dataSource = new DriverManagerDataSource("jdbc:h2:mem:test;DB_CLOSE_DELAY=-1"); // replace with your connection string or connection pool
StorageOperations storage = new RelaTableStorage(new JdbcTemplate(dataSource), "STORAGE", new FileBufferedBlobExtractor()); // can be customized, see Javadoc
storage.put(new PathResource("path/to/myFile.ext"), "myStoredFile.ext"); // the second argument can be prefixed to simulate a hierarchical structure
Resource resource = storage.get("myStoredFile.ext");
try (InputStream in = resource.getInputStream()) {
    byte[] bytes = in.readAllBytes(); // not intended for reading input streams with large amounts of data!
}

See also SampleCodeTest for a runnable JUnit test based on this code.