Package freemarker.template

Class SimpleHash

  • All Implemented Interfaces:
    TemplateHashModel, TemplateHashModelEx, TemplateHashModelEx2, TemplateModel, java.io.Serializable
    Direct Known Subclasses:
    AllHttpScopesHashModel, Environment.Namespace
    public class SimpleHash
extends WrappingTemplateModel
implements TemplateHashModelEx2, java.io.Serializable
    A simple implementation of the TemplateHashModelEx interface, using its own underlying Map or SortedMap for storing the hash entries. If you are wrapping an already existing Map, you should certainly use DefaultMapAdapter instead (see comparison below).

    This class is thread-safe if you don't call modifying methods (like put(String, Object), remove(String), etc.) after you have made the object available for multiple threads (assuming you have published it safely to the other threads; see JSR-133 Java Memory Model). These methods aren't called by FreeMarker, so it's usually not a concern.

    SimpleHash VS DefaultMapAdapter - Which to use when?

    For a Map that exists regardless of FreeMarker, only you need to access it from templates, DefaultMapAdapter should be the default choice, as it reflects the exact behavior of the underlying Map (no surprises), can be unwrapped to the originally wrapped object (important when passing it to Java methods from the template), and has more predictable performance (no spikes).

    For a hash that's made specifically to be used from templates, creating an empty SimpleHash then filling it with put(String, Object) is usually the way to go, as the resulting hash is significantly faster to read from templates than a DefaultMapAdapter (though it's somewhat slower to read from a plain Java method to which it had to be passed adapted to a Map).

    It also matters if for how many times will the same Map entry be read from the template(s) later, on average. If, on average, you read each entry for more than 4 times, SimpleHash will be most certainly faster, but if for 2 times or less (and especially if not at all) then DefaultMapAdapter will be faster. Before choosing based on performance though, pay attention to the behavioral differences; SimpleHash will shallow-copy the original Map at construction time, so key order will be lost in some cases, and it won't reflect Map content changes after the SimpleHash construction, also SimpleHash can't be unwrapped to the original Map instance.

    See Also:
    DefaultMapAdapter, TemplateHashModelEx, Serialized Form

    • Constructor Detail

      • SimpleHash

        @Deprecated
public SimpleHash​(java.util.Map map)
        Deprecated.
        Use SimpleHash(Map, ObjectWrapper)
        Creates a new simple hash with the copy of the underlying map and the default wrapper set in WrappingTemplateModel.setDefaultObjectWrapper(ObjectWrapper).
        Parameters:
        map - The Map to use for the key/value pairs. It makes a copy for internal use. If the map implements the SortedMap interface, the internal copy will be a TreeMap, otherwise it will be a HashMap.

      • SimpleHash

        public SimpleHash​(java.util.Map<java.lang.String,​java.lang.Object> directMap,
                  ObjectWrapper wrapper,
                  int overloadDistinction)
        Creates an instance that will use the specified Map directly as its backing store; beware, the Map will be possibly modified by SimpleHash, even if you only read the SimpleHash. That's because when a value is read, it's replaced with the corresponding TemplateModel.

        The goal of this constructor is to allow you to control technical aspects, like the initial capacity, and ordering of the underlying Map implementation. The iteration order of the SimpleHash will be the same as of the underlying Map.

        Parameters:
        directMap - The map that the instance will use directly as backing storage; possibly will be modified, even when you only read the SimpleHash! Must allow any kind of object as value, including null! Supporting null keys is not needed.
        overloadDistinction - To avoid ambiguity with other overloads; the value is unused.
        Since:
        2.3.30

      • SimpleHash

        public SimpleHash​(java.util.Map map,
                  ObjectWrapper wrapper)
        Creates a new hash by shallow-coping (possibly cloning) the underlying map; in many applications you should use DefaultMapAdapter instead.
        Parameters:
        map - The Map to use for the key/value pairs. It makes a copy for internal use. If the map implements the SortedMap interface, the internal copy will be a TreeMap, otherwise it will be a
        wrapper - The object wrapper to use to wrap contained objects into TemplateModel instances. Using null is deprecated but allowed, in which case the deprecated default wrapper set in WrappingTemplateModel.setDefaultObjectWrapper(ObjectWrapper) is used.

    • Method Detail

      • copyMap

        protected java.util.Map copyMap​(java.util.Map map)

      • put

        public void put​(java.lang.String key,
                java.lang.Object value)
        Adds a key-value entry to this hash.
        Parameters:
        key - The name by which the object is identified in the template.
        value - The value to which the name will be associated. This will only be wrapped to TemplateModel lazily when it's first read.

      • put

        public void put​(java.lang.String key,
                boolean b)
        Puts a boolean in the map
        Parameters:
        key - the name by which the resulting TemplateModel is identified in the template.
        b - the boolean to store.

      • containsKey

        public boolean containsKey​(java.lang.String key)
        Tells if the map contains a key or not, regardless if the associated value is null or not.
        Since:
        2.3.20

      • remove

        public void remove​(java.lang.String key)
        Removes the given key from the underlying map.
        Parameters:
        key - the key to be removed

      • putAll

        public void putAll​(java.util.Map m)
        Adds all the key/value entries in the map
        Parameters:
        m - the map with the entries to add, the keys are assumed to be strings.

      • toMap

        public java.util.Map toMap()
                    throws TemplateModelException
        Note that this method creates and returns a deep-copy of the underlying hash used internally. This could be a gotcha for some people at some point who want to alter something in the data model, but we should maintain our immutability semantics (at least using default SimpleXXX wrappers) for the data model. It will recursively unwrap the stuff in the underlying container.
        Throws:
        TemplateModelException

      • toString

        public java.lang.String toString()
        Returns the toString() of the underlying Map.
        Overrides:
        toString in class java.lang.Object

      • size

        public int size()
        Specified by:
        size in interface TemplateHashModelEx
        Returns:
        the number of key/value mappings in the hash.

      • synchronizedWrapper

        public SimpleHash synchronizedWrapper()