com.github.stefanbirkner.systemlambda

Class SystemLambda.WithEnvironmentVariables

java.lang.Object

com.github.stefanbirkner.systemlambda.SystemLambda.WithEnvironmentVariables

Enclosing class:

SystemLambda

public static final class SystemLambda.WithEnvironmentVariables
extends Object

A collection of values for environment variables. New values can be added by and(String, String). The EnvironmentVariables object is then used to execute an arbitrary piece of code with these environment variables being present.

Method Summary

Modifier and Type	Method and Description
SystemLambda.WithEnvironmentVariables	and(String name, String value) Creates a new WithEnvironmentVariables object that additionally stores the value for an additional environment variable.
<T> T	execute(Callable<T> callable) Executes a Callable with environment variable values according to what was set before.
void	execute(Statement statement) Executes a statement with environment variable values according to what was set before.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

and

public SystemLambda.WithEnvironmentVariables and(String name,
                                                 String value)

Creates a new WithEnvironmentVariables object that additionally stores the value for an additional environment variable.

You cannot specify the value of an environment variable twice. An IllegalArgumentException when you try.

Parameters:

name - the name of the environment variable.

value - the value of the environment variable.

Returns:

a new WithEnvironmentVariables object.

Throws:

IllegalArgumentException - when a value for the environment variable name is already specified.

See Also:

SystemLambda.withEnvironmentVariable(String, String), execute(Statement)

execute

public <T> T execute(Callable<T> callable)
              throws Exception

Executes a Callable with environment variable values according to what was set before. It exposes the return value of the Callable. All changes to environment variables are reverted after the Callable has been executed.

 @Test
 void execute_code_with_environment_variables(
 ) throws Exception {
    List<String> values = withEnvironmentVariable("first", "first value")
     .and("second", "second value")
     .and("third", null)
     .execute(() -> asList(
         System.getenv("first"),
         System.getenv("second"),
         System.getenv("third")
     ));
   assertEquals(
     asList("first value", "second value", null),
     values
   );
 }
 

Warning: This method uses reflection for modifying internals of the environment variables map. It fails if your SecurityManager forbids such modifications.

Type Parameters:

T - the type of callable's result

Parameters:

callable - an arbitrary piece of code.

Returns:

the return value of callable.

Throws:

Exception - any exception thrown by the callable.

Since:

1.1.0

See Also:

SystemLambda.withEnvironmentVariable(String, String), and(String, String), execute(Statement)

execute

public void execute(Statement statement)
             throws Exception

Executes a statement with environment variable values according to what was set before. All changes to environment variables are reverted after the statement has been executed.

 @Test
 void execute_code_with_environment_variables(
 ) throws Exception {
   withEnvironmentVariable("first", "first value")
     .and("second", "second value")
     .and("third", null)
     .execute(() -> {
       assertEquals(
         "first value",
         System.getenv("first")
       );
       assertEquals(
         "second value",
         System.getenv("second")
       );
       assertNull(
         System.getenv("third")
       );
     });
 }
 

Warning: This method uses reflection for modifying internals of the environment variables map. It fails if your SecurityManager forbids such modifications.

Parameters:

statement - an arbitrary piece of code.

Throws:

Exception - any exception thrown by the statement.

Since:

1.0.0

See Also:

SystemLambda.withEnvironmentVariable(String, String), and(String, String), execute(Callable)