Support for running functions over a result set.

json-path/src/main/java/com/jayway/jsonpath/internal/path/CompiledPath.java

@@ -50,7 +50,25 @@ public class CompiledPath implements Path {
         EvaluationContextImpl ctx = new EvaluationContextImpl(this, rootDocument, configuration, forUpdate);
         try {
             PathRef op = ctx.forUpdate() ?  PathRef.createRoot(rootDocument) : PathRef.NO_OP;
+
+            if (root.isFunctionPath()) {
+                // Remove the functionPath and evaluate the resulting path.
+                PathToken funcToken = root.chop();
+                root.evaluate("", op, document, ctx);
+                // Get the value of the evaluation to use as model when evaluating the function.
+                Object arrayModel = ctx.getValue(false);
+
+                // Evaluate the function on the model from the first evaluation.
+                RootPathToken newRoot = new RootPathToken('x');
+                newRoot.append(funcToken);
+                CompiledPath newCPath = new CompiledPath(newRoot, true);
+                EvaluationContextImpl newCtx = new EvaluationContextImpl(newCPath, arrayModel, configuration, false);
+                funcToken.evaluate("", op, arrayModel, newCtx);
+                return newCtx;
+            } else {
                 root.evaluate("", op, document, ctx);
+                return ctx;
+            }
         } catch (EvaluationAbortException abort){};
 
         return ctx;

json-path/src/main/java/com/jayway/jsonpath/internal/path/PathToken.java

@@ -36,6 +36,15 @@ public abstract class PathToken {
         return next;
     }
 
+    PathToken remove() {
+        prev.next = next;
+        if (next == null) {
+            return prev;
+        }
+        next.prev = prev;
+        return next;
+    }
+
     void handleObjectProperty(String currentPath, Object model, EvaluationContextImpl ctx, List<String> properties) {
 
         if(properties.size() == 1) {

json-path/src/main/java/com/jayway/jsonpath/internal/path/RootPathToken.java

@@ -43,6 +43,13 @@ public class RootPathToken extends PathToken {
         return this;
     }
 
+    public PathToken chop() {
+        // Remove tail.
+        PathToken oldTail = tail;
+        tail = tail.remove();
+        return oldTail;
+    }
+
     public PathTokenAppender getPathTokenAppender(){
         return new PathTokenAppender(){
             @Override

json-path/src/test/java/com/jayway/jsonpath/internal/function/BaseFunctionTest.java

@@ -14,6 +14,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 public class BaseFunctionTest {
     protected static final String NUMBER_SERIES = "{\"empty\": [], \"numbers\" : [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]}";
     protected static final String TEXT_SERIES = "{\"urls\": [\"http://api.worldbank.org/countries/all/?format=json\", \"http://api.worldbank.org/countries/all/?format=json\"], \"text\" : [ \"a\", \"b\", \"c\", \"d\", \"e\", \"f\" ]}";
+    protected static final String EXAMPLE_SERIES = "{\"store\":{\"book\":[{\"category\":\"reference\",\"author\":\"Nigel Rees\",\"title\":\"Sayings of the Century\",\"price\":8.95},{\"category\":\"fiction\",\"author\":\"Evelyn Waugh\",\"title\":\"Sword of Honour\",\"price\":12.99},{\"category\":\"fiction\",\"author\":\"Herman Melville\",\"title\":\"Moby Dick\",\"isbn\":\"0-553-21311-3\",\"price\":8.99},{\"category\":\"fiction\",\"author\":\"J. R. R. Tolkien\",\"title\":\"The Lord of the Rings\",\"isbn\":\"0-395-19395-8\",\"price\":22.99}],\"bicycle\":{\"color\":\"red\",\"price\":19.95}},\"expensive\":10}";
 
     /**
      * Verify the function returns the correct result based on the input expectedValue
@@ -40,6 +41,10 @@ public class BaseFunctionTest {
         verifyFunction(conf, pathExpr, TEXT_SERIES, expectedValue);
     }
 
+    protected void verifyExampleFunction(Configuration conf, String pathExpr, Object expectedValue) {
+        verifyFunction(conf, pathExpr, EXAMPLE_SERIES, expectedValue);
+    }
+
     protected String getResourceAsText(String resourceName) throws IOException {
         return new Scanner(BaseFunctionTest.class.getResourceAsStream(resourceName), "UTF-8").useDelimiter("\\A").next();
     }

json-path/src/test/java/com/jayway/jsonpath/internal/function/ResultSetFunctionTest.java

@@ -0,0 +1,45 @@
+package com.jayway.jsonpath.internal.function;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.runners.Parameterized.Parameters;
+
+import com.jayway.jsonpath.Configuration;
+import com.jayway.jsonpath.Configurations;
+import com.jayway.jsonpath.JsonPathException;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Defines functional tests around executing functions on result sets.
+ */
+@RunWith(Parameterized.class)
+public class ResultSetFunctionTest extends BaseFunctionTest {
+
+    private static final Logger logger = LoggerFactory.getLogger(ResultSetFunctionTest.class);
+
+    private Configuration conf = Configurations.GSON_CONFIGURATION;
+
+    public ResultSetFunctionTest(Configuration conf) {
+        logger.debug("Testing with configuration {}", conf.getClass().getName());
+        this.conf = conf;
+    }
+
+    @Parameters
+    public static Iterable<Configuration> configurations() {
+        return Configurations.configurations();
+    }
+
+    @Test
+    public void testMaxOfDoublesResultSet() {
+        verifyExampleFunction(conf, "$.store.book[*].price.max()", 22.99);
+    }
+
+    @Test
+    public void testSumOfDoublesResultSet() {
+        verifyExampleFunction(conf, "$.store.book[*].price.sum()", 53.92);
+    }
+
+}