E Getting Started with RESTful Services

This tutorial is designed to let you get started quickly developing RESTful services using Oracle REST Data Services. If you go through this tutorial before reading Developing Oracle REST Data Services Applications, you should later read that chapter to understand the main concepts and techniques presented there.

This tutorial is based on the following document that is included in the Oracle REST Data Services installation kit: <install-directory>\examples\getting-started\index.html. That document is among several resources supplied to help you become productive quickly, as explained in "Getting Started" Documents Included in Installation.

Before you perform the actions in this tutorial, note the following prerequisites and recommendations:

The examples in this tutorial assume the following:

  • Oracle REST Data Services has been installed and configured, and is running in standalone mode on the following server, port, and context path: localhost:8080/ords/

  • Oracle REST Data Services is configured to connect as its default connection to an Oracle database listening on localhost:1521, and the database has a service name of orcl.

This "getting started" tutorial has the following major steps:

  1. REST-Enable a Database Table

  2. Create a RESTful Service from a SQL Query

  3. Protect Resources

  4. Register an OAuth Client Application

E.1 REST-Enable a Database Table

To enable a table for REST access, follow these steps.

Tip:

It is recommended that you follow the steps as closely as possible, including using the specified names for schemas and database objects. After you have successfully completed the tutorial using this approach, feel free to try it again using other values if you wish.

  1. Create a database schema named ordstest for use in trying out RESTful services. In SQL Developer, connect to the database as sys and enter the following in the SQL Worksheet:

    CREATE USER ordstest IDENTIFIED BY <password>;
    GRANT "CONNECT" TO ordstest;
    GRANT "RESOURCE" TO ordstest;
    GRANT UNLIMITED TABLESPACE TO ordstest
    
  2. Connect to the ordstest schema. In SQL Developer create a connection to the ordstest schema, connect to it, and open a SQL worksheet.

  3. Create a database table. For example, enter the following in the SQL Worksheet to create an example table named EMP:

    CREATE TABLE EMP (
      EMPNO NUMBER(4,0), 
      ENAME VARCHAR2(10 BYTE), 
      JOB VARCHAR2(9 BYTE), 
      MGR NUMBER(4,0), 
      HIREDATE DATE, 
      SAL NUMBER(7,2), 
      COMM NUMBER(7,2), 
      DEPTNO NUMBER(2,0), 
      CONSTRAINT PK_EMP PRIMARY KEY (EMPNO)
      );
    
  4. Insert some sample data into the table. For example:

    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7369,'SMITH','CLERK',7902,to_date('17-DEC-80','DD-MON-RR'),800,null,20);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7499,'ALLEN','SALESMAN',7698,to_date('20-FEB-81','DD-MON-RR'),1600,300,30);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7521,'WARD','SALESMAN',7698,to_date('22-FEB-81','DD-MON-RR'),1250,500,30);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7566,'JONES','MANAGER',7839,to_date('02-APR-81','DD-MON-RR'),2975,null,20);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7654,'MARTIN','SALESMAN',7698,to_date('28-SEP-81','DD-MON-RR'),1250,1400,30);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7698,'BLAKE','MANAGER',7839,to_date('01-MAY-81','DD-MON-RR'),2850,null,30);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7782,'CLARK','MANAGER',7839,to_date('09-JUN-81','DD-MON-RR'),2450,null,10);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7788,'SCOTT','ANALYST',7566,to_date('19-APR-87','DD-MON-RR'),3000,null,20);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7839,'KING','PRESIDENT',null,to_date('17-NOV-81','DD-MON-RR'),5000,null,10);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7844,'TURNER','SALESMAN',7698,to_date('08-SEP-81','DD-MON-RR'),1500,0,30);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7876,'ADAMS','CLERK',7788,to_date('23-MAY-87','DD-MON-RR'),1100,null,20);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7900,'JAMES','CLERK',7698,to_date('03-DEC-81','DD-MON-RR'),950,null,30);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7902,'FORD','ANALYST',7566,to_date('03-DEC-81','DD-MON-RR'),3000,null,20);
    Insert into EMP (EMPNO,ENAME,JOB,MGR,HIREDATE,SAL,COMM,DEPTNO) values (7934,'MILLER','CLERK',7782,to_date('23-JAN-82','DD-MON-RR'),1300,null,10);
    commit;
    
  5. Enable the schema of the EMP table for REST. In SQL Developer, right-click the ordstest connection, and select REST Services > Enable RESTful Services to display the following wizard page:

    Enable schema: Enable this option.

    Schema alias: Accept ordstest for the schema alias.

    Authorization required: For simplicity, this tutorial does not require authorisation, so disable this option.

    Click Next.

  6. On the RESTful Summary page of the wizard, click Finish.

  7. Enable the EMP table for REST. In SQL Developer, right-click EMP table in the Connections navigator, and select REST Services > Enable RESTful Services to display the following wizard page:

    Enable object: Enable this option (that is, enable REST access for the EMP table).

    Object alias: Accept emp for the object alias.

    Authorization required: For simplicity, this tutorial does not require authorisation, so disable this option.

  8. On the RESTful Summary page of the wizard, click Finish.

    The EMP table is now exposed as a REST HTTP endpoint.

  9. Test the REST endpoint. In a web browser enter the following URL:

    http://localhost:8080/ords/ordstest/emp/
    
    • The ORDSTEST schema has been exposed at the /ordstest/ path.

    • The EMP table has been exposed at the /emp/ path.

    A JSON document similar to the following is displayed:

E.2 Create a RESTful Service from a SQL Query

Oracle REST Data Services provides a REST API (called the Resource Modules API) that enables Oracle SQL Developer to create and edit RESTful service definitions. Access to the Resource Modules API is protected, a user with the correct role must be provisioned, and the created user's credentials must be used when accessing the API from SQL Developer.

To create a RESTful service from a SQL query, follow these steps.

  1. In the folder where Oracle REST Data Services was installed, enter the following command at a command prompt:

    java -jar ords.war user test_developer "SQL Developer"
    
    • You will be prompted to enter a password.

    • This command creates a user named test_developer and grants the user the role named SQL Developer. Only users with the SQL Developer role are permitted to access the resource module's API.

    • The user details are stored in a file named credentials in the ORDS configuration folder. However, it is not recommended to store user credentials in the credentials file in production deployments; instead, users should be provisioned in the host application server.

    The remaining steps create and test the RESTful service.

  2. Create RESTful connection. In SQL Developer, select View > REST Data Services > Development.

  3. In the REST Development pane, right-click REST Data Services > Connect.

  4. In the RESTful Services Connection dialog box, click the + (plus sign) icon to add a connection to the list available for selection.

  5. In the New RESTful Services Connection dialog box, enter the necessary information:

    Connection Name: Any desired name for the connection. Example: ordstest

    Username: test_developer

    http or https: Select http for simplicity in this tutorial.

    Hostname: localhost

    Port: 8080

    Server Path: /ords

    Workspace: ordstest

    Click OK, then enter the password for the test_developer user at the prompt.

  6. Create the module. Right-click the Modules node in the REST Development view, click New Module, and enter information on the Specify Module page:

    Module Name: Any desired name for the connection. Example: test

    URI Prefix: /test

    Publish - Make this RESTful Service available for use: Enable (check).

    Pagination Size: 7

  7. Click Next, and enter information on the Specify Template page:

    URI Template: /emp/

    Accept the defaults for the remaining options.

  8. Click Next, and enter information on the Specify Handler page:

    Method: GET

    Requires Secure Access: Disable (uncheck) for this tutorial.

    Source Type: Collection Query

    Pagination Size: 7

  9. Click Next to go to the RESTful Summary page of the wizard, then click Finish.

    The resource module is now created, the next step is to define the query for the GET resource handler.

  10. Define the query for the GET resource handler.

    1. Expand the test node under the Modules node in the REST Development view.

    2. Expand the /emp/ node, right-click the GET node, and select Open.

    3. In the SQL Worksheet that opens for GET /emp/, enter the following SQL query:

      select * from emp
      
    4. Right-click on the test node under the 'Modules' node in the 'REST Development' view

    5. Click 'Upload...'. A confirmation dialog will appear confirming the module has been uploaded.

  11. Test the RESTful service. In a web browser enter the following URL:

    http:/localhost:8080/ords/ordtest/test/emp/
    
    • The ORDSTEST schema has been exposed at the /ordstest/ path.

    • The EMP table has been exposed at the /test/emp/ path.

    A JSON document similar to the following is displayed:

E.3 Protect Resources

Up to this point the tutorial has deliberately disabled security on the RESTful endpoints you created, because it is easier to test them without security. In this topic you protect the /test/emp/ service, requiring users to authenticate before accessing the service.

Controlling access to protected resources is done by defining privileges. Privileges restrict access to only users having at least one of a set of specified roles. A privilege is then associated with one or more resource modules: before those resource modules can be accessed, the user must be authenticated and then authorized to ensure that the user has one of the required roles.

To protect resources, follow these steps.

  1. Create a privilege. In SQL Developer, right-click the Privileges node in the REST Development view and select New Privileges to display the Edit Privilege dialog box:

    Name: test

    Title: Example Privilege

    Description: Demonstrate controlling access with privileges

    Protected Modules: Ensure that the list includes the test module. Use the arrow button to move it if necessary.

    Click Apply.

  2. Right click the test privilege and click Upload.

    A dialog box confirms that the privilege has been uploaded.

    You have now created a privilege that protects the test module. However, you have not restricted the privilege to any particular role; this will just require that the user be authenticated before accessing the test module (the next step).

  3. Test the RESTful service. In a web browser enter the following URL:
    http://localhost:8080/ords/ordstest/test/emp/
    
  4. Click the link to sign in, and enter the test_developer credentials.

    The contents of the JSON document are displayed.

E.4 Register an OAuth Client Application

This topic explains how to register your applications (called "third-party" applications here) to access a REST API.

OAuth 2.0 is a standard Internet protocol that provides a means for HTTP servers providing REST APIs to give limited access to third party applications on behalf of an end user.

  • The author of the third-party application must register the application to gain client credentials.

  • Using the client credentials the third party application starts a web flow that prompts the end-user to approve access.

So, before a third party application can access a REST API, it must be registered and the user must approve access. And before the application can be registered, it must be assigned a user identity that enables the user to register applications. Users possessing the SQL Developer role (such as the test_developer user created in Create a RESTful Service from a SQL Query) are permitted to register OAuth clients.

Tip:

In a real application, you may want to provision specific users that can register OAuth clients; these users should be granted the OAuth Client Developer role.

This topic outlines how to complete these actions. It is not a full-featured demonstration of how to create and integrate a third party application; it just outlines the concepts involved.

  1. Register the client application.

    1. In a web browser enter the following URL:

      http://localhost:8080/ords/ordstest/oauth/clients/
      
    2. At the prompt, click the link to sign in and enter the credentials for the test_developer user.

    3. Click New Client and enter the following information:

      Name: Test Client

      Description: An example OAuth Client

      Redirect URI: http://example.org/redirect

      Support e-mail: info@example.org

      Support URI: http://example.org/support

      Required Privileges: Example Privilege

    4. Click Create.

      The client registration is created, and the Authorization URI for the client is displayed. You have created a client that will use the Implicit Grant authorization flow (explained at https://tools.ietf.org/html/rfc6749#section-4.2).

      Note the Client Identifier assigned to the client and the Authorization URI value. These values are used to start the authorization flow (next major step).

  2. Approve the client application.

    In a real third-party client application, the client will initiate the approval flow by directing a web browser to the Authorization URI. The end user will be prompted to sign in and approve access to the client application. The browser will be redirected back to the client's registered Redirect URI with a URI fragment containing the access_token for the approval. To simulate this process:

    1. In a web browser, enter the Authorization URI that you noted in the previous step. The URL should look like the following (though you should not copy and paste in this example value):

      http://localhost:8080/ords/ordstest/oauth/auth?response_type=token&client_id=5B77A34A266EFB0056BE3497ED7099.&state=d5b7944-d27d-8e2c-4d5c-fb80e1114490&_auth_=force
      

      The client_id value must be the value of the client identifier assigned to the application. Be sure you are using the correct client_id value. Do not use the value in the preceding example; replace it with the client identifier assigned to your application.

      The state value should be a unique, unguessable value that the client remembers, and can use later to confirm that the redirect received from Oracle REST Data Services is in response to this authorisation request. This value is used to prevent Cross Site Request Forgery attacks; it is very important, cannot be omitted, and must not be guessable or discoverable by an attacker.

    2. At the prompt, click the link to sign in and enter the credentials for the test_developer user.

    3. Review the access being requested, and click Approve.

      The browser is redirected to a URL similar to the following:

      http://example.org/redirect#token_type=bearer&access_token=-i_Ows8j7JYu0p07jOFMEA..&expires_in=3600
      

      When registering the OAuth client, you specified http://example.org/redirect as the Redirect URI. On completion of the approval request, the browser is redirected to this registered redirect URI. Appended to the URI is the information about the access token that was generated for the approval.

      In a real application, the third party application would respond to the redirect to the redirect URI by caching the access token, redirecting to another page to show the user that they are now authorized to access the REST API, and including the access token in every subsequent request to the REST API. However, in this tutorial you just make note of the access token value and manually create a HTTP request with the access token included, as explained in the next major step.

      The value of the access token (which in the preceding example is -i_Ows8j7JYu0p07jOFMEA..) will change on every approval.

      Note that the access token expires. In the preceding example it expires after 3600 seconds (&expires_in=3600), that is, one hour.

  3. Issue an authorized request.

    After an access token has been acquired, the client application must remember the access token and include it with every request to the protected resource. The access token must be included in the HTTP Authorization request header (explained at http://tools.ietf.org/html/rfc2616#section-14.8) as in the following example:

    Host: localhost:8080
    GET /ords/ordstest/test/emp/
    Authorization: Bearer -i_Ows8j7JYu0p07jOFMEA..
    

    To emulate creating a valid HTTP request, use the cURL command line tool (if necessary, install cURL using http://curl.haxx.se/). In a real application this request would be performed by the client making an HTTP request, such as an XMLHttpRequest. For example:

    curl -i -H'Authorization: Bearer -i_Ows8j7JYu0p07jOFMEA..' http://localhost:8080/ords/ordstest/test/emp/
    

    However, in this example replace -i_Ows8j7JYu0p07jOFMEA.. with the access token value that you previously noted.

    Output similar to the following JSON document should be displayed:

    HTTP/1.1 200 OK
    Content-Type: application/json
    Transfer-Encoding: chunked
     
    {
     "items":[
      {"empno":7369,"ename":"SMITH","job":"CLERK","mgr":7902,"hiredate":"1980-12-17T00:00:00Z","sal":800,"comm":null,"deptno":20},
      {"empno":7499,"ename":"ALLEN","job":"SALESMAN","mgr":7698,"hiredate":"1981-02-20T00:00:00Z","sal":1600,"comm":300,"deptno":30},
      {"empno":7521,"ename":"WARD","job":"SALESMAN","mgr":7698,"hiredate":"1981-02-22T00:00:00Z","sal":1250,"comm":500,"deptno":30},
      {"empno":7566,"ename":"JONES","job":"MANAGER","mgr":7839,"hiredate":"1981-04-01T23:00:00Z","sal":2975,"comm":null,"deptno":20},
      {"empno":7654,"ename":"MARTIN","job":"SALESMAN","mgr":7698,"hiredate":"1981-09-27T23:00:00Z","sal":1250,"comm":1400,"deptno":30},
      {"empno":7698,"ename":"BLAKE","job":"MANAGER","mgr":7839,"hiredate":"1981-04-30T23:00:00Z","sal":2850,"comm":null,"deptno":30},
      {"empno":7782,"ename":"CLARK","job":"MANAGER","mgr":7839,"hiredate":"1981-06-08T23:00:00Z","sal":2450,"comm":null,"deptno":10}
     ],
     "hasMore":true,
     "limit":7,
     "offset":0,
     "count":7,
     "links":[
      {"rel":"self","href":"http://localhost:8080/ords/ordstest/test/emp/"},
      {"rel":"describedby","href":"http://localhost:8080/metadata-catalog/test/emp/"},
      {"rel":"first","href":"http://localhost:8080/ords/ordstest/test/emp/"},
      {"rel":"next","href":"http://localhost:8080/ords/ordstest/test/emp/?offset=7"}
     ]
    }
    

    However, if the Authorization header is omitted, then the status 401 Unauthorized is returned instead.