JSON, SQLite & Persistence

Daniel Oskarsson Know IT

Preface

24 slides and Netbeans Demo

Contents are more towards avoiding pitfalls than learning the basics.

"Simplicity"

JSON

json.org

http://www.json.org

+ -

json

xml

size validation

validation size

JAX-RS JAX-WS

public class Tv { @GET @Path("/tv/") @Produces({"application/json"}) public List<Channel> getChannels() { List<Channel> channels = getChannels(); return channels; }}

JAX-B

@XmlRootElementpublic class Channel { public Channel() {} @XmlElement private String id; @XmlElement private String name; @XmlElement public String getLogo() { return String.format(path, id); } @XmlElement public List<Program> getPrograms() { return getPrograms(); }}

{

"channel":[

{

"id":"svt1.svt.se",

"name":"SVT1",

"logo":"svt1.svt.se.png",

"programs":[

{

"name":"Kulturnyheterna",

"start":"2011-11-23T18:00:00Z",

"stop":"2011-11-23T18:15:00Z"

},

{

"name":"Regionala nyheter",

"start":"2011-11-23T18:15:00Z",

"stop":"2011-11-23T18:30:00Z"

}

]

}]}

SQLite

sqlite.org

SQLite

"SQLite is a software library that implements a self-contained, server-less, zero-configuration, transactional SQL database engine"

"SQLite does not have a separate server process"

"SQLite reads and writes directly to ordinary disk files"

"Think of SQLite not as a replacement for Oracle but as a replacement for fopen()"

http://www.sqlite.org/about.html

Storage Classes

Values are one of the following storage classes:

INTEGER (signed) REAL TEXT (UTF) NULL BLOB

BOOL (INTEGER 0 or INTEGER 1)DATE (ISO8601 TEXT or Unix Time INTEGER or Julian days)TIME (ISO8601 TEXT or Unix Time INTEGER or Julian days)

http://www.sqlite.org/datatype3.html

Type Affinity

Columns are one the following type affinities:

INTEGERREALNUMERICTEXT (NULL, BLOB)NONE

Internally values may be casted before stored

http://www.sqlite.org/datatype3.html

http://www.sqlite.org/lang_createtable.html

Foreign keys

"Foreign key constraints are disabled by default (for backwards compatibility), so must be enabled separately for each database connection separately." (http://www.sqlite.org/foreignkeys.html)Class.forName("org.sqlite.JDBC");final String url = "jdbc:sqlite:json.db";

SQLiteConfig config = new SQLiteConfig();config.enforceForeignKeys(true);

Connection connection = DriverManager.getConnection(url, config.toProperties());

As an in-memory-database

Class.forName("org.sqlite.JDBC");final String url = "jdbc:sqlite::memory:";Connection connection = DriverManager.getConnection(url);

JDBC

http://www.xerial.org/trac/Xerial/wiki/SQLiteJDBC

<dependency> <groupId>org.xerial</groupId> <artifactId>sqlite-jdbc</artifactId></dependency>

1+1=3

JSON Persistence Framework

github.com/danieloskarsson/json-persistence

Characteristics

Key-value-based persistence

Zero configuration No database setup No mappings

No modifications of domain objects No serializable No annotations

Apache 2.0 License

Design decisions

Serialization & Deserialization JSON Serialization and Deserialization is NOT provided The user selects their favorite JSON library for the task

Versioning is NOT supported Some JSON libraries support versioning Some JSON libraries navigates the tree of the desired type As opposed to navigating the tree of the input

The data type is used as the key / id E.g. tv.domain.Channel[] or tv.domain.Channel Multiple instance of the same class must be in a list JSON should be parsed before it is persisted

A perfect match with Smartphones

SmartPhones often...

Comes bundled with support for JSONComes bundled with support for SQLiteReceive JSON data from a REST call

JSON Persistence Framework is forthcoming on Android iOS Windows Phone

github.com/danieloskarsson

linkedin.com/in/danieloskarsson