org.apache.juneau.svl.vars.EnvVariablesVar Maven / Gradle / Ivy

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package org.apache.juneau.svl.vars;

import org.apache.juneau.svl.*;

/**
 * Environment variable variable resolver.
 *
 * 
 * The format for this var is "$E{envVar[,defaultValue]}".
 *
 * 
Example:
 * 
 * 	// Create a variable resolver that resolves environment variables (e.g. "$E{PATH}")
 * 	VarResolver varResolver = VarResolver.create().vars(EnvVariablesVar.class).build();
 *
 * 	// Use it!
 * 	System.out.println(varResolver.resolve("Environment variable PATH is set to $E{PATH}"));
 * 
 *
 * 
 * Since this is a {@link SimpleVar}, any variables contained in the result will be recursively resolved.
 * 
Likewise, if the arguments contain any variables, those will be resolved before they are passed to this var.
 *
 * 
See Also:

 * 	Simple Variable Language
 * 
 */
public class EnvVariablesVar extends DefaultingVar {

	/** The name of this variable. */
	public static final String NAME = "E";

	/**
	 * Constructor.
	 */
	public EnvVariablesVar() {
		super(NAME);
	}

	@Override /* Var */
	public String resolve(VarResolverSession session, String varVal) {
		// Note that lookup is case-insensitive on windows.
		return System.getenv(varVal);
	}
}