fixed array slizing.

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

@@ -14,6 +14,7 @@
  */
 package com.jayway.jsonpath.internal.filter;
 
+import com.jayway.jsonpath.InvalidPathException;
 import com.jayway.jsonpath.spi.JsonProvider;
 
 import java.util.List;
@@ -27,44 +28,73 @@ public class ArrayIndexFilter extends PathTokenFilter {
     private static final Pattern SINGLE_ARRAY_INDEX_PATTERN = Pattern.compile("\\[\\d+\\]");
     private static final Pattern COMMA = Pattern.compile(",");
     private static final Pattern SPACE = Pattern.compile(" ");
+    private static final String OPERATOR = ":";
 
-    
     private final String trimmedCondition;
-    
+    private boolean usesLenght;
+
     public ArrayIndexFilter(String condition) {
         super(condition);
+
+        // remove '[' and ']'
         String trimmedCondition = trim(condition, 1, 1);
 
-        if(trimmedCondition.contains("@.length")){
+        this.usesLenght = trimmedCondition.contains("@.length");
+
+        // resolve '@.length'
+        if(usesLenght){
             trimmedCondition = trim(trimmedCondition, 1, 1);
             trimmedCondition = trimmedCondition.replace("@.length", "");
-            trimmedCondition = trimmedCondition + ":";
+            trimmedCondition = trimmedCondition + OPERATOR;
         }
         this.trimmedCondition = trimmedCondition;
     }
 
+
     @Override
     public Object filter(Object obj,JsonProvider jsonProvider) {
 
         List<Object> src = jsonProvider.toList(obj);
         List<Object> result = jsonProvider.createList();
 
-        
+        if (trimmedCondition.contains(OPERATOR)) {
+            if (trimmedCondition.startsWith(OPERATOR)) {
+                String trimmedCondition = trim(this.trimmedCondition, 1, 0);
+                int get = Integer.parseInt(trimmedCondition);
+                for (int i = 0; i < get; i++) {
+                    result.add(src.get(i));
+                }
+                return result;
 
+            } else if (trimmedCondition.endsWith(OPERATOR)) {
+                String trimmedCondition = trim(SPACE.matcher(this.trimmedCondition).replaceAll(""), 0, 1);
+                int get = Integer.parseInt(trimmedCondition);
+                if(get > 0 || usesLenght){
+                    if(get > 0){
+                        get = get * -1;
+                    }
+                    return src.get(src.size() + get);
+                } else {
+                    int start = src.size() + get;
+                    int stop = src.size();
+
+                    for (int i = start; i < stop; i ++){
+                        result.add(src.get(i));
+                    }
+                    return result;
+                }
 
-        if (trimmedCondition.startsWith(":")) {
-            String trimmedCondition = trim(this.trimmedCondition, 1, 0);
-            int get = Integer.parseInt(trimmedCondition);
-            for (int i = 0; i < get; i++) {
-                result.add(src.get(i));
-            }
-            return result;
+            } else {
+                String[] indexes = this.trimmedCondition.split(OPERATOR);
 
-        } else if (trimmedCondition.endsWith(":")) {
-            String trimmedCondition = trim(SPACE.matcher(this.trimmedCondition).replaceAll(""), 1, 1);
-            int get = Integer.parseInt(trimmedCondition);
-            return src.get(src.size() - get);
+                int start = Integer.parseInt(indexes[0]);
+                int stop = Integer.parseInt(indexes[1]);
 
+                for (int i = start; i < stop; i ++){
+                    result.add(src.get(i));
+                }
+                return result;
+            }
         } else {
             String[] indexArr = COMMA.split(trimmedCondition);
 

json-path/src/test/java/com/jayway/jsonpath/ArraySlicingTest.java

@@ -0,0 +1,92 @@
+package com.jayway.jsonpath;
+
+import org.hamcrest.Matchers;
+import org.junit.Test;
+
+import java.util.List;
+
+import static junit.framework.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+
+/**
+ * User: kalle
+ * Date: 8/20/13
+ * Time: 9:22 AM
+ *
+ * If you have a list
+ * nums = [1, 3, 5, 7, 8, 13, 20]
+ * then it is possible to slice by using a notation similar to element retrieval:
+ *
+ * nums[3]   #equals 7, no slicing
+ * nums[:3]  #equals [1, 3, 5], from index 0 (inclusive) until index 3 (exclusive)
+ * nums[1:5] #equals [3, 5, 7, 8]
+ * nums[-3:] #equals [8, 13, 20]
+ * nums[3:] #equals [8, 13, 20]
+ *
+ * Note that Python allows negative list indices. The index -1 represents the last element, -2 the penultimate element, etc.
+ * Python also allows a step property by appending an extra colon and a value. For example:
+ *
+ * nums[3::]  #equals [7, 8, 13, 20], same as nums[3:]
+ * nums[::3]  #equals [1, 7, 20] (starting at index 0 and getting every third element)
+ * nums[1:5:2] #equals [3, 7] (from index 1 until index 5 and getting every second element)
+
+ *
+ */
+public class ArraySlicingTest {
+
+    public static final String JSON_ARRAY = "[1, 3, 5, 7, 8, 13, 20]";
+
+    @Test
+    public void get_by_position(){
+        int result = JsonPath.read(JSON_ARRAY, "$[3]");
+        assertEquals(7, result);
+    }
+
+    @Test
+    public void get_from_index(){
+        List<Integer> result = JsonPath.read(JSON_ARRAY, "$[:3]");
+        assertThat(result, Matchers.contains(1,3,5));
+    }
+
+    @Test
+    public void get_between_index(){
+        List<Integer> result = JsonPath.read(JSON_ARRAY, "$[1:5]");
+        assertThat(result, Matchers.contains(3, 5, 7, 8));
+    }
+
+    @Test
+    public void get_between_index_2(){
+        List<Integer> result = JsonPath.read(JSON_ARRAY, "$[0:1]");
+        assertThat(result, Matchers.contains(1));
+    }
+
+    @Test(expected = IndexOutOfBoundsException.class)
+    public void get_between_index_out_of_bounds(){
+        List<Integer> result = JsonPath.read(JSON_ARRAY, "$[1:15]");
+    }
+
+    @Test
+    public void get_from_tail_index(){
+        List<Integer> result = JsonPath.read(JSON_ARRAY, "$[-3:]");
+        assertThat(result, Matchers.contains(8, 13, 20));
+    }
+
+    @Test
+    public void get_from_tail(){
+        int result = JsonPath.read(JSON_ARRAY, "$[3:]");
+        assertEquals(8, result);
+    }
+
+    @Test
+    public void get_from_tail_length(){
+        int result = JsonPath.read(JSON_ARRAY, "$[(@.length -3)]");
+        assertEquals(8, result);
+    }
+
+    @Test
+    public void get_indexes(){
+        List<Integer> result = JsonPath.read(JSON_ARRAY, "$[0,1,2]");
+        assertThat(result, Matchers.contains(1,3,5));
+    }
+
+}

json-path/src/test/java/com/jayway/jsonpath/ComplianceTest.java

@@ -8,6 +8,7 @@ import java.util.Map;
 
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.assertThat;
+import static org.junit.Assert.assertTrue;
 
 /**
  * test defined in http://jsonpath.googlecode.com/svn/trunk/tests/jsonpath-test-js.html
@@ -44,7 +45,10 @@ public class ComplianceTest {
                 new Double(3.14),
                 new Boolean(true),
                 (Comparable)null));
-        assertThat(JsonPath.<Boolean>read(json, "$[-1:]"), is(equalTo(null)));
+
+        List<Object> res = JsonPath.read(json, "$[-1:]");
+
+        assertTrue(res.get(0) == null);
     }
 
     @Test

json-path/src/test/java/com/jayway/jsonpath/JsonPathTest.java

@@ -190,7 +190,7 @@ public class JsonPathTest {
     public void access_array_by_index_from_tail() throws Exception {
 
         assertThat(JsonPath.<String>read(DOCUMENT, "$..book[(@.length-1)].author"), equalTo("J. R. R. Tolkien"));
-        assertThat(JsonPath.<String>read(DOCUMENT, "$..book[-1:].author"), equalTo("J. R. R. Tolkien"));
+        assertThat(JsonPath.<String>read(DOCUMENT, "$..book[1:].author"), equalTo("J. R. R. Tolkien"));
     }
 
     @Test