EnvironmentProperty

public interface EnvironmentProperty<T>

TraceContributorEnvironmentProperty<T>, ProcessEnvEnvironmentProperty, SystemPropertyEnvironmentProperty, UserParameterEnvironmentProperty

Specifies a property which can be derived from the build environment.

Properties are used to determine various aspects of the current build environment. They do not depend on the current build configuration, but only depend on the environment of the executing computer.

Implementations are required to override equals(Object) and hashCode(). Property implementations acts as a key to determine what they compute from the given environment.

Task implementations can use these classes to depend on various aspects of the build environment. If any of the dependent properties changes, the task will be rerun with appropriate deltas.

It is assumed that environment properties stay the same between consecutive build executions.

It is strongly recommended that implementations and the calculated property values implement the Externalizable interface.

Good examples for environment properties:

Current Java Runtime version.
Version of the used compiler for a given language.
Underlying operating system type.
Environment user parameters.

Bad examples for environment properties:

Current working directory.
Execution user parameters.

For these kind of properties, ExecutionProperty should be used.

TThe type of the returned property.

TaskContext.reportEnvironmentDependency(EnvironmentProperty<T>, T)

SakerEnvironment.getEnvironmentPropertyCurrentValue(EnvironmentProperty<T>)

TaskExecutionUtilities.getReportEnvironmentDependency(EnvironmentProperty<T>)

Methods

public boolean	equals(Object obj) Determines if this property will compute the same values as the parameter.
public T	getCurrentValue(SakerEnvironment environment) Computes the value of this environment property.
public int	hashCode() Returns a hash code value for the object.

public abstract boolean equals(Object obj)

Determines if this property will compute the same values as the parameter.

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.

@RMIForbidden

public abstract T getCurrentValue(SakerEnvironment environment) throws Exception

Computes the value of this environment property.

It is strongly recommended for the returned value to implement equals(Object) in order for proper incremental functionality.

environmentThe environment to use for the computation.

The computed value.

ExceptionIf any exception happens during the computation of the property.

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)