[feature] Add the function util:available-system-properties#0

Author: adamretter

exist-core/src/main/java/org/exist/ExistSystemProperties.java

@@ -24,6 +24,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Properties;
+import java.util.Set;
 
 import com.evolvedbinary.j8fu.lazy.AtomicLazyVal;
 import net.jcip.annotations.ThreadSafe;
@@ -74,4 +75,13 @@ public String getExistSystemProperty(final String propertyName) {
     public String getExistSystemProperty(final String propertyName, final String defaultValue) {
         return properties.get().getProperty(propertyName, defaultValue);
     }
+
+    /**
+     * Get the available eXist System Properties.
+     *
+     * @return the available eXist System Properties.
+     */
+    public Set<String> getAvailableExistSystemProperties() {
+        return properties.get().stringPropertyNames();
+    }
 }

exist-core/src/main/java/org/exist/xquery/functions/util/SystemProperty.java

@@ -29,9 +29,12 @@
 import org.exist.xquery.value.Sequence;
 import org.exist.xquery.value.StringValue;
 import org.exist.xquery.value.Type;
+import org.exist.xquery.value.ValueSequence;
 
-import static org.exist.xquery.FunctionDSL.param;
-import static org.exist.xquery.FunctionDSL.returnsOpt;
+import java.util.HashSet;
+import java.util.Set;
+
+import static org.exist.xquery.FunctionDSL.*;
 import static org.exist.xquery.functions.util.UtilModule.functionSignature;
 
 /**
@@ -42,8 +45,18 @@
  */
 public class SystemProperty extends BasicFunction {
 
-    public final static FunctionSignature signature = functionSignature(
-            "system-property",
+    private final static String FS_AVAILABLE_SYSTEM_PROPERTIES_NAME = "available-system-properties";
+    public final static FunctionSignature FS_AVAILABLE_SYSTEM_PROPERTIES = functionSignature(
+            FS_AVAILABLE_SYSTEM_PROPERTIES_NAME,
+            "Returns a list of available system properties. " +
+                    "Predefined properties are: vendor, vendor-url, product-name, product-version, product-build, and all Java " +
+                    "System Properties.",
+            returnsOptMany(Type.STRING, "The names of the available system properties")
+    );
+
+    private final static String FS_SYSTEM_PROPERTY_NAME = "system-property";
+    public final static FunctionSignature FS_SYSTEM_PROPERTY = functionSignature(
+            FS_SYSTEM_PROPERTY_NAME,
             "Returns the value of a system property. Similar to the corresponding XSLT function. " +
                     "Predefined properties are: vendor, vendor-url, product-name, product-version, product-build, and all Java " +
                     "System Properties.",
@@ -57,11 +70,26 @@ public SystemProperty(final XQueryContext context, final FunctionSignature signa
 
     @Override
     public Sequence eval(final Sequence[] args, final Sequence contextSequence) throws XPathException {
-        final String key = args[0].getStringValue();
-        String value = ExistSystemProperties.getInstance().getExistSystemProperty(key, null);
-        if (value == null) {
-            value = context.getJavaSystemProperties().get(key, null);
+        if (isCalledAs(FS_AVAILABLE_SYSTEM_PROPERTIES_NAME)) {
+
+            final Set<String> availableProperties = new HashSet<>();
+            availableProperties.addAll(ExistSystemProperties.getInstance().getAvailableExistSystemProperties());
+            availableProperties.addAll(context.getJavaSystemProperties().keys().toSet());
+
+            final ValueSequence result = new ValueSequence(availableProperties.size());
+            for (final String availableProperty : availableProperties) {
+                result.add(new StringValue(this, availableProperty));
+            }
+
+            return result;
+
+        } else {
+            final String key = args[0].getStringValue();
+            String value = ExistSystemProperties.getInstance().getExistSystemProperty(key, null);
+            if (value == null) {
+                value = context.getJavaSystemProperties().get(key, null);
+            }
+            return value == null ? Sequence.EMPTY_SEQUENCE : new StringValue(this, value);
         }
-        return value == null ? Sequence.EMPTY_SEQUENCE : new StringValue(this, value);
     }
-}
+}

exist-core/src/main/java/org/exist/xquery/functions/util/UtilModule.java

@@ -98,7 +98,8 @@ public class UtilModule extends AbstractInternalModule {
             new FunctionDef(ExclusiveLockFunction.signature, ExclusiveLockFunction.class),
             new FunctionDef(SharedLockFunction.signature, SharedLockFunction.class),
             new FunctionDef(Collations.signature, Collations.class),
-            new FunctionDef(SystemProperty.signature, SystemProperty.class),
+            new FunctionDef(SystemProperty.FS_AVAILABLE_SYSTEM_PROPERTIES, SystemProperty.class),
+            new FunctionDef(SystemProperty.FS_SYSTEM_PROPERTY, SystemProperty.class),
             new FunctionDef(FunctionFunction.signature, FunctionFunction.class),
             new FunctionDef(CallFunction.signature, CallFunction.class),
             new FunctionDef(NodeId.signature, NodeId.class),