org.apache.tinkerpop.gremlin

## Interface GraphProvider

- All Known Implementing Classes:
    AbstractFileGraphProvider, AbstractGraphProvider, GraphManager.ManagedGraphProvider

      public interface GraphProvider

  Those developing Gremlin implementations must provide a GraphProvider implementation so that the different test suites know how to instantiate their implementations. Implementers may choose to have multiple `GraphProvider` implementations to mix and match with multiple test suite implementations. For example, create one `GraphProvider` that has no indices defined and a separate `GraphProvider` that has indices. Then create separate test suite implementations for each `GraphProvider`. This approach will have the test suites executed once for each `GraphProvider` ensuring that the `Graph` implementation works under multiple configurations. Consider making these "extra" tests "integration tests" so that they don't have to be executed on every run of the build so as to save time. Run the "integration tests" periodically to ensure overall compliance.
  Author:
    Stephen Mallette (http://stephen.genoprime.com)

- - ### Nested Class Summary

    Nested Classes
    Modifier and Type | Interface and Description
    --- | ---
    `static interface` | `GraphProvider.Descriptor` An annotation to be applied to a `GraphProvider` implementation that provides additional information about its intentions.
    `static interface` | `GraphProvider.TestListener`

  - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static Set<Class>` | `CORE_IMPLEMENTATIONS` Implementations from `gremlin-core` that need to be part of the clear process.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Default Methods
    Modifier and Type | Method and Description
    --- | ---
    `default void` | `clear(Configuration configuration)` If possible (usually with persisted graph) clear the space on disk given the configuration that would be used to construct the graph.
    `void` | `clear(Graph graph, Configuration configuration)` Clears a `Graph` of all data and settings.
    `default Object` | `convertId(Object id, Class<? extends Element> c)` Converts an identifier from a test to an identifier accepted by the `Graph` instance.
    `default String` | `convertLabel(String label)` Converts an label from a test to an label accepted by the Graph instance.
    `default GraphComputer` | `getGraphComputer(Graph graph)` Create a `GraphComputer` from the `Graph` instance.
    `Set<Class>` | `getImplementations()` Get the set of concrete implementations of certain classes and interfaces utilized by the test suite.
    `default Optional<Graph.Features>` | `getStaticFeatures()` Gets a `Graph.Features` implementation that contains graph feature configuration that will never change from execution to execution of the tests given this current `GraphProvider` implementation.
    `default Optional<GraphProvider.TestListener>` | `getTestListener()` Returns a `GraphProvider.TestListener` implementation that provides feedback to the `GraphProvider` implementation.
    `default String` | `getWorkingDirectory()` Helper method for those build `GraphProvider` implementations that need a standard working directory for tests (e.g.
    `void` | `loadGraphData(Graph graph, LoadGraphWith loadGraphWith, Class testClass, String testName)` Tests are annotated with a `LoadGraphWith` annotation.
    `default Configuration` | `newGraphConfiguration(String graphName, Class<?> test, String testMethodName, LoadGraphWith.GraphData loadGraphWith)` When implementing this method ensure that a test suite can override any settings EXCEPT the "gremlin.graph" setting which should be defined by the implementer.
    `Configuration` | `newGraphConfiguration(String graphName, Class<?> test, String testMethodName, Map<String,Object> configurationOverrides, LoadGraphWith.GraphData loadGraphWith)` When implementing this method ensure that a test suite can override any settings EXCEPT the "gremlin.graph" setting which should be defined by the implementer.
    `default Graph` | `openTestGraph(Configuration config)` Creates a new `Graph` instance from the `org.apache.commons.configuration.Configuration` object using `GraphFactory`.
    `default Configuration` | `standardGraphConfiguration(Class<?> test, String testMethodName, LoadGraphWith.GraphData loadGraphWith)` Gets the `Configuration` object that can construct a `Graph` instance from `GraphFactory`.
    `default Graph` | `standardTestGraph(Class<?> test, String testMethodName, LoadGraphWith.GraphData loadGraphWith)` Creates a new `Graph` instance using the default `org.apache.commons.configuration.Configuration` from `standardGraphConfiguration(Class, String, LoadGraphWith.GraphData)`.
    `default GraphTraversalSource` | `traversal(Graph graph)` Create a `GraphTraversalSource` from a `Graph` instance.
    `default GraphTraversalSource` | `traversal(Graph graph, TraversalStrategy... strategies)` Create a `GraphTraversalSource` from a `Graph` instance.

- - ### Field Detail

    - #### CORE_IMPLEMENTATIONS

          static final Set<Class> CORE_IMPLEMENTATIONS

      Implementations from `gremlin-core` that need to be part of the clear process. This does not exempt providers from having to register their extensions to any of these classes, but does prevent them from having to register them in addition to their own.

  - ### Method Detail

    - #### traversal

          default GraphTraversalSource traversal(Graph graph)

      Create a `GraphTraversalSource` from a `Graph` instance. The default implementation does not use `GraphComputer` so providers should override as necessary if their implementation is testing something that requires a different engine type, like `GraphComputer`.

    - #### traversal

          default GraphTraversalSource traversal(Graph graph,
                                                 TraversalStrategy... strategies)

      Create a `GraphTraversalSource` from a `Graph` instance. The default implementation does not use `GraphComputer` so providers should override as necessary if their implementation is testing something that requires a different engine type, like `GraphComputer`.

      Implementations should apply strategies as necessary to the `GraphTraversalSource` before calling it's `create` method.

    - #### getGraphComputer

          default GraphComputer getGraphComputer(Graph graph)

      Create a `GraphComputer` from the `Graph` instance. The default implementation simply calls `graph.compute()`.
      Parameters:
        `graph` - the graph to get the graph computer from
      Returns:
        a new graph computer

    - #### standardTestGraph

          default Graph standardTestGraph(Class<?> test,
                                          String testMethodName,
                                          LoadGraphWith.GraphData loadGraphWith)

      Creates a new `Graph` instance using the default `org.apache.commons.configuration.Configuration` from `standardGraphConfiguration(Class, String, LoadGraphWith.GraphData)`.

    - #### openTestGraph

          default Graph openTestGraph(Configuration config)

      Creates a new `Graph` instance from the `org.apache.commons.configuration.Configuration` object using `GraphFactory`. The assumption here is that the `Configuration` has been created by one of the `newGraphConfiguration(String, Class, String, LoadGraphWith.GraphData)` methods and has therefore already been modified by the implementation as necessary for `Graph` creation.

    - #### standardGraphConfiguration

          default Configuration standardGraphConfiguration(Class<?> test,
                                                           String testMethodName,
                                                           LoadGraphWith.GraphData loadGraphWith)

      Gets the `Configuration` object that can construct a `Graph` instance from `GraphFactory`. Note that this method should create a `Graph` using the `graphName` of "standard", meaning it should always return a configuration instance that generates the same `Graph` from the `GraphFactory`.

    - #### clear

          default void clear(Configuration configuration)
                      throws Exception

      If possible (usually with persisted graph) clear the space on disk given the configuration that would be used to construct the graph. The default implementation simply calls `#clear(Graph, org.apache.commons.configuration.Configuration)` with a null graph argument.

      Implementations should be able to accept an argument of null for the `org.apache.commons.configuration.Configuration` as well, and a proper handling is needed. Otherwise, a NullPointerException may be thrown.
      Throws:
        `Exception`

    - #### clear

          void clear(Graph graph,
                     Configuration configuration)
              throws Exception

      Clears a `Graph` of all data and settings. Implementations will have different ways of handling this. It is typically expected that `Graph.close()` will be called and open transactions will be closed. For a brute force approach, implementers can simply delete data directories provided in the configuration. Implementers may choose a more elegant approach if it exists.

      Implementations should be able to accept an argument of null for the `Graph`, in which case the only action that can be performed is a clear given the configuration. The method will typically be called this way as clean up task on setup to ensure that a persisted graph has a clear space to create a test graph.

      Implementations should be able to accept an argument of null for the `org.apache.commons.configuration.Configuration` as well, and a proper handling is needed. Otherwise, a NullPointerException may be thrown.

      Calls to this method may occur multiple times for a specific test. Develop this method to be idempotent.
      Throws:
        `Exception`

    - #### convertId

          default Object convertId(Object id,
                                   Class<? extends Element> c)

      Converts an identifier from a test to an identifier accepted by the `Graph` instance. Test that try to utilize an Element identifier will pass it to this method before usage. This method should be sure to be consistent in the return value such that calling it with "x" should always return the same transformed value.

    - #### convertLabel

          default String convertLabel(String label)

      Converts an label from a test to an label accepted by the Graph instance. Test that try to utilize a label will pass it to this method before usage.

    - #### newGraphConfiguration

          Configuration newGraphConfiguration(String graphName,
                                              Class<?> test,
                                              String testMethodName,
                                              Map<String,Object> configurationOverrides,
                                              LoadGraphWith.GraphData loadGraphWith)

      When implementing this method ensure that a test suite can override any settings EXCEPT the "gremlin.graph" setting which should be defined by the implementer. It should provide a `Configuration` that will generate a graph unique to that `graphName`.
      Parameters:
        `graphName` - a unique test graph name
        `test` - the test class
        `testMethodName` - the name of the test
        `configurationOverrides` - settings to override defaults with.
        `loadGraphWith` - the data set to load and will be null if no data is to be loaded

    - #### newGraphConfiguration

          default Configuration newGraphConfiguration(String graphName,
                                                      Class<?> test,
                                                      String testMethodName,
                                                      LoadGraphWith.GraphData loadGraphWith)

      When implementing this method ensure that a test suite can override any settings EXCEPT the "gremlin.graph" setting which should be defined by the implementer. It should provide a `Configuration` that will generate a graph unique to that `graphName`.
      Parameters:
        `graphName` - a unique test graph name
        `test` - the test class
        `testMethodName` - the name of the test
        `loadGraphWith` - the data set to load and will be null if no data is to be loaded

    - #### loadGraphData

          void loadGraphData(Graph graph,
                             LoadGraphWith loadGraphWith,
                             Class testClass,
                             String testName)

      Tests are annotated with a `LoadGraphWith` annotation. These annotations tell the test what kind of data to preload into the graph instance. It is up to the implementation to load the graph with the data specified by that annotation. This method also represents the place where indices should be configured according the the `Graph` implementation's API. Implementers can use the `testClass` and `testName` arguments to implement test specific configurations to their graphs.
      Parameters:
        `graph` - the `Graph` instance to load data into constructed by this `GraphProvider`
        `loadGraphWith` - the annotation for the currently running test - this value may be null if no graph data is to be loaded in front of the test.
        `testClass` - the test class being executed
        `testName` - the name of the test method being executed

    - #### getImplementations

          Set<Class> getImplementations()

      Get the set of concrete implementations of certain classes and interfaces utilized by the test suite. This method should return any implementations or extensions of the following interfaces or classes:
      - `Edge`
      - `Element`
      - `DefaultGraphTraversal`
      - `Graph`
      - `Graph.Variables`
      - `GraphTraversal`
      - `B_LP_O_P_S_SE_SL_Traverser`
      - `Property`
      - `B_O_S_SE_SL_Traverser`
      - `Traversal`
      - `Traverser`
      - `Vertex`
      - `VertexProperty`

      The test suite only enforces registration of the following core structure interfaces (i.e. these classes must be registered or the tests will fail to execute):
      - `Edge`
      - `Element`
      - `Graph`
      - `Graph.Variables`
      - `Property`
      - `Vertex`
      - `VertexProperty`

      The remaining interfaces and classes should be registered however as failure to do so, might cause failures in the Groovy environment testing suite.

      Internally speaking, tests that make use of this method should bind in `CORE_IMPLEMENTATIONS` to the `Set` because these represent `gremlin-core` implementations that are likely not registered by the vendor implementations.

    - #### getWorkingDirectory

          default String getWorkingDirectory()

      Helper method for those build `GraphProvider` implementations that need a standard working directory for tests (e.g. graphs that persist data to disk). Typically, there is no need to override the default behavior of this method and if it is overridden, it is usually best to continue to use the `TestHelper` to produce the working directory as it will create the path in the appropriate build directories.

    - #### getTestListener

          default Optional<GraphProvider.TestListener> getTestListener()

      Returns a `GraphProvider.TestListener` implementation that provides feedback to the `GraphProvider` implementation. By default, this returns an empty listener.

    - #### getStaticFeatures

          default Optional<Graph.Features> getStaticFeatures()

      Gets a `Graph.Features` implementation that contains graph feature configuration that will never change from execution to execution of the tests given this current `GraphProvider` implementation. Implementing this method will allow the test suite to avoid creation of a `Graph` instance and thus speed up the execution of tests if that creation process is expensive. It is important that this static set of features be representative of what the `Graph` instance produced by this `GraphProvider` can actually do or else the cost of `Graph` instantiation will be incurred when it doesn't need to be. It is also important that this method be faster than the cost of `Graph` creation in the first place or there really won't be any difference in execution speed. In cases where some features are static and others are not, simply throw an `UnsupportedOperationException` from those features to let the test suite know that it cannot rely on them and the test suite will revert to using a constructed `Graph` instance.

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