freemarker.template.TemplateDirectiveModel Maven / Gradle / Ivy
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* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package freemarker.template;
import java.io.IOException;
import java.util.Map;
import freemarker.core.Environment;
import freemarker.template.utility.DeepUnwrap;
/**
* "directive" template language data type: used as user-defined directives
* (much like macros) in templates. They can do arbitrary actions, write arbitrary
* text to the template output, and trigger rendering of their nested content for
* any number of times.
*
* They are used in templates like {@code <@myDirective foo=1 bar="wombat">...} (or as
* {@code <@myDirective foo=1 bar="wombat" />} - the nested content is optional).
*
* @since 2.3.11
*/
public interface TemplateDirectiveModel extends TemplateModel {
/**
* Executes this user-defined directive; called by FreeMarker when the user-defined
* directive is called in the template.
*
*
This method should not throw {@link RuntimeException}, nor {@link IOException} that wasn't caused by writing
* to the output. Such exceptions should be catched inside the method and wrapped inside a
* {@link TemplateException}. (Note that setting {@link Configuration#setWrapUncheckedExceptions(boolean)} to
* {@code true} can mitigate the negative effects of implementations that throw {@link RuntimeException}-s.)
*
* @param env the current processing environment. Note that you can access
* the output {@link java.io.Writer Writer} by {@link Environment#getOut()}.
* @param params the parameters (if any) passed to the directive as a
* map of key/value pairs where the keys are {@link String}-s and the
* values are {@link TemplateModel} instances. This is never
* null. If you need to convert the template models to POJOs,
* you can use the utility methods in the {@link DeepUnwrap} class.
* @param loopVars an array that corresponds to the "loop variables", in
* the order as they appear in the directive call. ("Loop variables" are out-parameters
* that are available to the nested body of the directive; see in the Manual.)
* You set the loop variables by writing this array. The length of the array gives the
* number of loop-variables that the caller has specified.
* Never null, but can be a zero-length array.
* @param body an object that can be used to render the nested content (body) of
* the directive call. If the directive call has no nested content (i.e., it's like
* <@myDirective /> or <@myDirective></@myDirective>), then this will be
* null.
*
* @throws TemplateException If any problem occurs that's not an {@link IOException} during writing the template
* output.
* @throws IOException When writing the template output fails. Other {@link IOException}-s should be catched in this
* method and wrapped into {@link TemplateException}.
*/
void execute(Environment env, Map params, TemplateModel[] loopVars,
TemplateDirectiveBody body) throws TemplateException, IOException;
}