Expose a way to add custom path functions with minimal impact

README.md

@@ -506,8 +506,45 @@ CacheProvider.setCache(new Cache() {
 });
 ```
 
+### Custom PAth Functions
 
+If you want to implement you own path functions, create your PathFunction implementation.
+Initializing PathFunctionFactory should only be done when your application is being initialized.
 
+```java
+
+class MyPathFunction implements PathFunction {
+
+	public static final String NAME = "mypathfunc";
+
+	@Override
+	public Object invoke(
+		String currentPath,
+		PathRef parent,
+		Object model,
+		EvaluationContext ctx,
+		List<Parameter> parameters
+	) {
+		// Do something here
+
+		return model;
+	}
+}
+
+// Example application initialization
+class ApplicationBoot {
+	public static void main(String[] args) {
+
+		PathFunctionFactory.add(
+			MyPathFunction.NAME,
+			MyPathFunction.class
+		);
+
+		PathFunctionFactory.init();
+	}
+}
+
+```
 
 
 

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

@@ -29,6 +29,20 @@ public class PathFunctionFactory {
 
     static {
         // New functions should be added here and ensure the name is not overridden
+        Map<String, Class> map = getFunctions();
+
+        FUNCTIONS = Collections.unmodifiableMap(map);
+    }
+
+    /**
+     * Returns the common/core functions.
+     *
+     * @see #FUNCTIONS
+     * @see PathFunction
+     *
+     * @return Map of path functions keyed by name
+     */
+    public static Map<String, Class> getFunctions() {
         Map<String, Class> map = new HashMap<String, Class>();
 
         // Math Functions
@@ -47,11 +61,11 @@ public class PathFunctionFactory {
         map.put("append", Append.class);
         map.put("keys", KeySetFunction.class);
 
-
-        FUNCTIONS = Collections.unmodifiableMap(map);
+        return map;
     }
 
     /**
+     * @deprecated
      * Returns the function by name or throws InvalidPathException if function not found.
      *
      * @see #FUNCTIONS

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

@@ -3,7 +3,7 @@ package com.jayway.jsonpath.internal.path;
 import com.jayway.jsonpath.internal.PathRef;
 import com.jayway.jsonpath.internal.function.Parameter;
 import com.jayway.jsonpath.internal.function.PathFunction;
-import com.jayway.jsonpath.internal.function.PathFunctionFactory;
+import com.jayway.jsonpath.PathFunctionFactory;
 import com.jayway.jsonpath.internal.function.latebinding.JsonLateBindingValue;
 import com.jayway.jsonpath.internal.function.latebinding.PathLateBindingValue;