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      1 /*
      2  * Copyright (C) 2012 The Android Open Source Project
      3  *
      4  * Licensed under the Eclipse Public License, Version 1.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.eclipse.org/org/documents/epl-v10.php
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 package com.android.ide.eclipse.adt.internal.wizards.templates;
     18 
     19 import static com.android.tools.lint.detector.api.LintUtils.assertionsEnabled;
     20 
     21 import com.android.annotations.NonNull;
     22 import com.android.annotations.Nullable;
     23 import com.android.ide.eclipse.adt.AdtPlugin;
     24 
     25 import freemarker.cache.TemplateLoader;
     26 import freemarker.template.Configuration;
     27 import freemarker.template.DefaultObjectWrapper;
     28 import freemarker.template.Template;
     29 
     30 import java.io.IOException;
     31 import java.io.Reader;
     32 import java.io.StringReader;
     33 import java.io.StringWriter;
     34 import java.util.List;
     35 import java.util.Map;
     36 
     37 /**
     38  * A template handler which can evaluate simple strings. Used to evaluate
     39  * parameter constraints during UI wizard value editing.
     40  * <p>
     41  * Unlike the more general {@link TemplateHandler} which is used to instantiate
     42  * full template files (from resources, merging into existing files etc) this
     43  * evaluator supports only simple strings, referencing only values from the
     44  * provided map (and builtin functions).
     45  */
     46 class StringEvaluator implements TemplateLoader {
     47     private Map<String, Object> mParameters;
     48     private Configuration mFreemarker;
     49     private String mCurrentExpression;
     50 
     51     StringEvaluator() {
     52         mParameters = TemplateHandler.createBuiltinMap();
     53 
     54         mFreemarker = new Configuration();
     55         mFreemarker.setObjectWrapper(new DefaultObjectWrapper());
     56         mFreemarker.setTemplateLoader(this);
     57     }
     58 
     59     /** Evaluates the given expression, with the given set of parameters */
     60     @Nullable
     61     String evaluate(@NonNull String expression, @NonNull List<Parameter> parameters) {
     62         // Render the instruction list template.
     63         for (Parameter parameter : parameters) {
     64             mParameters.put(parameter.id, parameter.value);
     65         }
     66         try {
     67             mCurrentExpression = expression;
     68             Template inputsTemplate = mFreemarker.getTemplate(expression);
     69             StringWriter out = new StringWriter();
     70             inputsTemplate.process(mParameters, out);
     71             out.flush();
     72             return out.toString();
     73         } catch (Exception e) {
     74             if (assertionsEnabled()) {
     75                 AdtPlugin.log(e, null);
     76             }
     77             return null;
     78         }
     79     }
     80 
     81     // ---- Implements TemplateLoader ----
     82 
     83     @Override
     84     public Object findTemplateSource(String name) throws IOException {
     85         return mCurrentExpression;
     86     }
     87 
     88     @Override
     89     public long getLastModified(Object templateSource) {
     90         return 0;
     91     }
     92 
     93     @Override
     94     public Reader getReader(Object templateSource, String encoding) throws IOException {
     95         return new StringReader(mCurrentExpression);
     96     }
     97 
     98     @Override
     99     public void closeTemplateSource(Object templateSource) throws IOException {
    100     }
    101 }
    102