Package oracle.dbtools.plugin.api.di

Enum AvailableDependencies

java.lang.Object

java.lang.Enum<AvailableDependencies>

oracle.dbtools.plugin.api.di.AvailableDependencies

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<AvailableDependencies>

public enum AvailableDependencies
extends java.lang.Enum<AvailableDependencies>

Enumerates the publicly available services that can be injected into plugins via the Inject annotation on a type's constructor. Unless otherwise noted these services will always be available.

Author:

cdivilly

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Enum Constant Summary

Enum Constants

Enum Constant	Description
ANNOTATIONS	Provide an API for working with Annotation instances.
CONFIGURATION	Provides a Configuration instance appropriate for the backing store that the current request is targeted to.
CONNECTION	Provides a Connection connected to the appropriate database pool and schema, inferred from mapping the request URL.
INSTANCE_LOCATOR	Provides an API for discovering at run-time the available implementations of a service.
IO	Provides IOStreams service for manipulating input and output streams.
JSON	Provides access to the JSONStreams service, which can be used to parse character streams into JSON (using JSONReader) and to generate JSON using JSONWriter.
JSON_OBJECTS	Provides access to the JSONObjects service, which can be used to build in memory representations of JSON object graphs.
LOCALE	Provides the most preferred Locale for a request
LOCALE_PREFERENCE	Provides a LocalePreference instance, which enumerates the preferred Locales for a request from most to least preferred.
LOG	Provides access to the the JDK Logger service.
PATH_TEMPLATES	Provides methods for working with PathTemplateMatch instances

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Method Summary

Modifier and Type	Method	Description
java.lang.annotation.Annotation[]	constraints()	The Annotations that may constrain the scope of the dependency
java.lang.Class<?>	type()	The type of the dependency
static AvailableDependencies	valueOf(java.lang.String name)	Returns the enum constant of this type with the specified name.
static AvailableDependencies[]	values()	Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait </section>

<section role="region">

Enum Constant Detail

ANNOTATIONS

public static final AvailableDependencies ANNOTATIONS

Provide an API for working with Annotation instances. This API may be useful in unit tests to define expected Annotation values.

Usage

 @Provides
 class SomeTestFixture {
   @Inject
   SomeTestFixture(Annotations annotations) {
     this.expectedNamedAnnotation = annotations.literal(Named.class,"foo");
   }
   ...
 }
 

CONFIGURATION

public static final AvailableDependencies CONFIGURATION

Provides a Configuration instance appropriate for the backing store that the current request is targeted to. If this service is called from an ApplicationScoped service, then the global configuration is used.

Usage

 @Provides
 @Dispatches(@PathTemplate("/some/service"))
 class SomeService extends HttpServlet {
   @Inject
   SomeService(Configuration conf) {
     this.conf = conf;
   }
 
   public void doGet(HttpServletRequest request,
       HttpServletResponse response) throws ServletException, IOException {
     String setting = conf.get(SOME_CONFIG_SETTING);
     response.getWriter()
         .println("The value of the setting is: " + setting);
   }
 
   private final Configuration conf;
 
   private final static String SOME_CONFIG_SETTING = "my.really.important.setting";
 }
 

The above example retrieves the value of the setting and displays it in the response.

N.B. Care must be exercised when working with Configuration instances to ensure that a vector to reveal sensitive configuration data is not created. For example if the value of my.really.important.setting is sensitive, then printing it's value in the response to a GET request is entirely inappropriate and dangerous. Similarly any code that allows an attacker to control over displaying of configuration data in the delivered response is dangerous.

CONNECTION

public static final AvailableDependencies CONNECTION

Provides a Connection connected to the appropriate database pool and schema, inferred from mapping the request URL. This dependency will only be available during processing of requests that have been mapped to a JDBC backing store.

Usage

 @Provides
 @Dispatches(@PathTemplate("/some/service"))
 class SomeService extends HttpServlet {
   @Inject
   SomeService(Connection conn) {
     this.conn = conn;
   }
 
   public void doGet(HttpServletRequest request,
       HttpServletResponse response) throws ServletException, IOException {
     PreparedStatement ps = conn.prepareStatement(
         "select sys_context('USERENV','CURRENT_USER') from dual");
     ResultSet rs = ps.execute();
     rs.next();
     String user = rs.getString(1);
     response.getWriter().println("mapped database user is: " + user);
     rs.close();
     ps.close();
   }
 
   private final Connection conn;
 }
 

A Connection can only be injected for request URLs where the runtime has been able to the map the URL to a database pool and schema. If the runtime was not able to map the URL to a database/schema, then it will not attempt to dispatch a service that depends on Connection, even if it's URL pattern matches the request URL.

For example attempting to access the above service at:

 http://localhost:8080/ords/some/service
 

Will result in a 404 Not Found status because the URL does not contain enough information to identify a database/schema to map to.

By contrast, the following URL:

 http://localhost:8080/ords/test_schema/some/service
 

Will execute correctly assuming a schema named test_schema exists in the default database pool

IO

public static final AvailableDependencies IO

Provides IOStreams service for manipulating input and output streams.

JSON

public static final AvailableDependencies JSON

Provides access to the JSONStreams service, which can be used to parse character streams into JSON (using JSONReader) and to generate JSON using JSONWriter.

JSON_OBJECTS

public static final AvailableDependencies JSON_OBJECTS

Provides access to the JSONObjects service, which can be used to build in memory representations of JSON object graphs.

LOCALE

public static final AvailableDependencies LOCALE

Provides the most preferred Locale for a request

LOCALE_PREFERENCE

public static final AvailableDependencies LOCALE_PREFERENCE

Provides a LocalePreference instance, which enumerates the preferred Locales for a request from most to least preferred.

LOG

public static final AvailableDependencies LOG

Provides access to the the JDK Logger service. All Logging must be done through this service.

Usage

 @Provides
 class SomeService {
   @Inject
   SomeService(Logger log) {
     this.log = log;
   }
 
   public void someMethod() {
     log.info("doing something");
   }
 
   private final Logger log;
 }
 

PATH_TEMPLATES

public static final AvailableDependencies PATH_TEMPLATES

Provides methods for working with PathTemplateMatch instances

Usage

 @Provides
 class SomeService {
   @Inject
   SomeService(PathTemplates pathTemplates) {
     this.pathTemplates = pathTemplates;
   }
 
   private final PathTemplates pathTemplates;
 }
 

INSTANCE_LOCATOR

public static final AvailableDependencies INSTANCE_LOCATOR

Provides an API for discovering at run-time the available implementations of a service. Typically it is preferred to directly inject service implementations via an @Inject annotated constructor, but there are occasional use cases where it can be useful to locate dependencies dynamically at run-time. For example it may be necessary to discover if a given dependency is available or has multiple providers.

Usage of this API should be limited as overuse implies reliance on the Service Locator Pattern rather than the Dependency Injection Pattern.

Usage

 @Provides
 class SomeService {
   @Inject
   SomeService(InstanceLocator locator) {
     boolean widgetAvailable = !locator.select(Widget.class)
         .isUnsatisfied();
   }
 
   public void someMethod() {
     if (widgetAvailable) {
       // go down the preferred code path
     } else {
       // go down a fallback code path
     }
   }
 }
 

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Method Detail

values

public static AvailableDependencies[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (AvailableDependencies c : AvailableDependencies.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static AvailableDependencies valueOf(java.lang.String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

java.lang.IllegalArgumentException - if this enum type has no constant with the specified name

java.lang.NullPointerException - if the argument is null

constraints

public java.lang.annotation.Annotation[] constraints()

The Annotations that may constrain the scope of the dependency

Returns:

Annotations that the depedency must be matche against

type

public java.lang.Class<?> type()

The type of the dependency

Returns:

dependency type

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