ContentDescriptorSupplier

public interface ContentDescriptorSupplier

Interface for customizing the algorithm of creating the default content descriptor for files on the file system.

Implementations of this interface is mainly used by ContentDatabase to specify how the differences in file contents will be handled. The common implementations include logic for creating content descriptors based on file attributes (size, modification time) or hashing the file contents (MD5).

Implementations should adhere to the equals(Object) and hashCode() contract.

DatabaseConfiguration

ContentDatabase

Methods

public boolean	equals(Object obj) Checks if this supplier will calculate the same content descriptors as the parameter given the same circumstances.
public ContentDescriptor	get(ProviderHolderPathKey pathkey) Creates the content descriptor for the given location.
public default ContentDescriptor	getCalculatedOutput(ProviderHolderPathKey pathkey, ByteSink calculatingoutput) Computes the content descriptor based on the data calculated.
public default ByteSink	getCalculatingOutput() Creates a content descriptor calculating output.
public default ContentDescriptor	getUsingFileAttributes(ProviderHolderPathKey pathkey, BasicFileAttributes attrs) Creates the content descriptor for a file, optionally using the provided attributes.
public default ContentDescriptor	getUsingFileContent(ProviderHolderPathKey pathkey, ByteArrayRegion bytes, BasicFileAttributes attrs) Creates the content descriptor for a file, optionally using the provided contents or attributes.
public int	hashCode() Returns a hash code value for the object.

public abstract boolean equals(Object obj)

Checks if this supplier will calculate the same content descriptors as the parameter given the same circumstances.

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

It is reflexive: for any non-null reference value x, x.equals(x) should return true.
It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

true if this object is the same as the obj argument; false otherwise.

public abstract ContentDescriptor get(ProviderHolderPathKey pathkey) throws IOException

Creates the content descriptor for the given location.

pathkeyThe file location.

The content descriptor.

IOExceptionIn case of I/O error.

public default ContentDescriptor getCalculatedOutput(ProviderHolderPathKey pathkey, ByteSink calculatingoutput) throws IOException

Computes the content descriptor based on the data calculated.

pathkeyThe location of the file.

calculatingoutputThe output which was returned from getCalculatingOutput() and has the file contents written to.

The content descriptor.

IOExceptionIn case of I/O error.

public default ByteSink getCalculatingOutput()

Creates a content descriptor calculating output.

Implementations can return a custom output stream which will receive the contents of the file. The getCalculatedOutput(ProviderHolderPathKey, ByteSink) function will be called after the file writing is done, and the implementation can instantiate the content descriptor based on the calculated data.

This functionality is optional, not required to be supported by implementations.

Implementing this function for content hash based implementations can improve performance.

The output or null if this functionality is not supported.

public default ContentDescriptor getUsingFileAttributes(ProviderHolderPathKey pathkey, BasicFileAttributes attrs) throws IOException

Creates the content descriptor for a file, optionally using the provided attributes.

pathkeyThe file location.

attrsThe attributes of the file.

The content descriptor.

IOExceptionIn case of I/O error.

public default ContentDescriptor getUsingFileContent(ProviderHolderPathKey pathkey, ByteArrayRegion bytes, BasicFileAttributes attrs) throws IOException

Creates the content descriptor for a file, optionally using the provided contents or attributes.

pathkeyThe file location.

bytesThe raw byte content of the file.

attrsThe file attributes, or null if it is not available (null attributes doesn't mean that the file doesn't exist).

The content descriptor.

IOExceptionIn case of I/O error.

public abstract int hashCode()

Overridden from: Object

Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

The general contract of hashCode is:

Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
It is not required that if two objects are unequal according to the Object.equals(Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java™ programming language.)

a hash code value for this object.

Object.equals(Object)

System.identityHashCode(Object)