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JDBI からJSON Services のデータアクセスオブジェクトを作成

JDBI でJSON services 用のSQL オブジェクトAPIを作成する方法を概説します。

JDBI は、Fluent スタイルとSQL オブジェクトスタイルという2つの異なるスタイルAPI を公開する、Java 用のSQL コンビニエンスライブラリです。CData JDBC Driver for JSON は、Java アプリケーションとリアルタイムJSON services のデータ連携を実現します。これらの技術を組み合わせることによって、JSON services へのシンプルなコードアクセスが可能になります。ここでは、基本的なDAO(Data Access Object )とそれに付随するJSON services の読み書きのためのコードの作成について説明します。

JSON people Entity のDAO を作成

The interface below declares the desired behavior for the SQL object to create a single method for each SQL statement to be implemented.

public interface MypeopleDAO { //insert new data into JSON @SqlUpdate("INSERT INTO people ([ personal.name.last ], [ personal.name.last ]) values (:[ personal.name.last ], :[ personal.name.last ])") void insert(@Bind("[ personal.name.last ]") String [ personal.name.last ], @Bind("[ personal.name.last ]") String [ personal.name.last ]); //request specific data from JSON (String type is used for simplicity) @SqlQuery("SELECT [ personal.name.last ] FROM people WHERE [ personal.name.last ] = :[ personal.name.last ]") String find[ personal.name.last ]By[ personal.name.last ](@Bind("[ personal.name.last ]") String [ personal.name.last ]); /* * close with no args is used to close the connection */ void close(); }

JSON への接続を開く

Collect the necessary connection properties and construct the appropriate JDBC URL for connecting to JSON.

See the Getting Started chapter in the data provider documentation to authenticate to your data source: The data provider models JSON APIs as bidirectional database tables and JSON files as read-only views (local files, files stored on popular cloud services, and FTP servers). The major authentication schemes are supported, including HTTP Basic, Digest, NTLM, OAuth, and FTP. See the Getting Started chapter in the data provider documentation for authentication guides.

After setting the URI and providing any authentication values, set DataModel to more closely match the data representation to the structure of your data.

The DataModel property is the controlling property over how your data is represented into tables and toggles the following basic configurations.

  • Document (default): Model a top-level, document view of your JSON data. The data provider returns nested elements as aggregates of data.
  • FlattenedDocuments: Implicitly join nested documents and their parents into a single table.
  • Relational: Return individual, related tables from hierarchical data. The tables contain a primary key and a foreign key that links to the parent document.

See the Modeling JSON Data chapter for more information on configuring the relational representation. You will also find the sample data used in the following examples. The data includes entries for people, the cars they own, and various maintenance services performed on those cars.

ビルトイン接続文字列デザイナー

For assistance in constructing the JDBC URL, use the connection string designer built into the JSON JDBC Driver.Either double-click the JAR file or execute the jar file from the command-line.

java -jar cdata.jdbc.json.jar

Fill in the connection properties and copy the connection string to the clipboard.

A connection string for JSON will typically look like the following:

jdbc:json:URI=C:\people.json;DataModel=Relational;

Use the configured JDBC URL to obtain an instance of the DAO interface.The particular method shown below will open a handle bound to the instance, so the instance needs to be closed explicitly to release the handle and the bound JDBC connection.

DBI dbi = new DBI("jdbc:json:URI=C:\people.json;DataModel=Relational;"); MypeopleDAO dao = dbi.open(MypeopleDAO.class); //do stuff with the DAO dao.close();

JSON Services について

With the connection open to JSON, simply call the previously defined method to retrieve data from the people entity in JSON.

//disply the result of our 'find' method String [ personal.name.last ] = dao.find[ personal.name.last ]By[ personal.name.last ]("Roberts"); System.out.println([ personal.name.last ]);

JSON Services の書き方

It is also simple to write data to JSON, using the previously defined method.

//add a new entry to the people entity dao.insert(new[ personal.name.last ], new[ personal.name.last ]);

Since the JDBI library is able to work with JDBC connections, you can easily produce a SQL Object API for JSON by integrating with the CData JDBC Driver for JSON.Download a free trial and work with live JSON services in custom Java applications today.

 
 
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