What is it?
-----------

A tool to parse an arbitrarily large JSON file into a Microsoft SQL Server database.

Quick Start
-----------

To set up, extract `JsonImport_jar.zip` to a directory, then use the following command:

    usage: java -jar JsonImport.jar -f <fieldNames> -s <server> -d <database>
    -i <file> [OPTIONS]
    -B <blockSize>     number of JSON objects per thread. If empty, it
                       defaults to 500.
    -d <database>      name of the database to import to.
    -f <fieldNames>    comma separated list of column names to import. Values
                       are imported from JSON objects' matching field names.
    -I <instance>      instance name of the SQL server.
    -i <fileName>      file path of the JSON import file.
    -N <threadCount>   number of threads to use. If empty, it defaults to
                       number of processors available.
    -P <port>          port of the SQL server. If empty, it defaults to 1433.
    -p <password>      password to log in to database.
    -s <server>        server name of the SQL server. Do not include instance
                       name.
    -T <table>         name of the table to import to. If empty, it defaults
                       to name of JSON array.
    -u <user>          username to log in to database.
    
For example, to import auctions.json to table Listings on SQL server instance SERVER1\SQLEXPRESS, using 10 threads:

    java -jar JsonImport.jar -f "ListingId, Title, StartPrice" -s SERVER1 -I SQLEXPRESS -P 1434 -d Auction
    -T Listings -u robo -p hunter13 -N 10 -i C:\Users\Robo\auctions.json

Usage Guide
-----------

The tool will verify the fields specified exist in the database table, then processes the file concurrently by
creating blocks of JSON objects then passing them to a thread executor.

The tool uses its 'best effort' to perform the import, i.e. it will:

* Continue to read the JSON array if it encounters an non-object
* Assign null value if a field is missing in a JSON object
* Assign default value if the JSON value type is not compatible with the database field
* Continues if it encounters an exception when importing an object

The tool will import the first array it finds in the JSON file, i.e. the array can be nested inside objects or come
after other fields in the file. It will skip any nodes in the array that is not an object.

For example, if the import table's field type is correct, the tool will import the 'auctions' array in the
following text without errors:

    {
    "realm":{"name":"Aegwynn","slug":"aegwynn"},
    "alliance":{"auctions":[
    {"auc":2073382230,"item":[1, 2, 3],"owner":"Keely"},
    "random string",
    {"auc":2073949971,"item":52364,"owner":"Facepwnded"},
    {"auc":2073218804,"item":23107,"owner":"Tephelie"}]}
    }
    }

Using SQL Server with named instances
-------------------------------------

Microsoft SQL Server defaults to listen on port 1433, but a named instance will listen on a different port. This can
be found by looking at the SQL Server log file in SQL Server Management Studio > Management > SQL Server Logs.
Look for something like `Server is listening on [ 'any' <ipv4> 56866]`. In this case, 56866 is the port number.

Alternatively, one can start the SQL Server Browser service, which listens on port 1434. Connections to port 1434
will get redirected to the correct SQL Server port.

Third party packages
--------------------

The tool uses the following third party packages:

    commons-cli-1.2.jar            Apache Commons CLI for parsing command line options.
    jackson-core-2.2.0.jar         Jackson JSON Processor for parsing JSON file.
    jackson-annotations-2.2.0.jar
    jackson-databind-2.2.0
    jtds-1.3.1.jar                 jTDS JDBC Driver for connecting to Microsoft SQL Server.