org.jdbi.v3.stringtemplate3.StringTemplateSqlLocator Maven / Gradle / Ivy

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jdbi-string-template locates SQL statements in StringTemplate files on the classpath
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/*
 * Licensed 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 org.jdbi.v3.stringtemplate3;

import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.nio.charset.Charset;
import java.util.Map;
import java.util.concurrent.TimeUnit;

import net.jodah.expiringmap.ExpirationPolicy;
import net.jodah.expiringmap.ExpiringMap;

import org.antlr.stringtemplate.StringTemplateGroup;

/**
 * Locates SQL in .sql.stg StringTemplate group files on the classpath.
 */
public class StringTemplateSqlLocator {
    private static final Map, StringTemplateGroup> CACHE = ExpiringMap.builder()
            .expiration(10, TimeUnit.MINUTES)
            .expirationPolicy(ExpirationPolicy.ACCESSED)
            .entryLoader(o -> readStringTemplateGroup((Class) o))
            .build();

    private static final Charset UTF_8 = Charset.forName("UTF-8");
    private static final String TEMPLATE_GROUP_EXTENSION = ".sql.stg";

    private StringTemplateSqlLocator() {
    }

    /**
     * Locates SQL for the given type and name. Example: Given a type com.foo.Bar and a name of
     * baz, loads a StringTemplate group file from the resource named com/foo/Bar.sql.stg on
     * the classpath, and returns the template with the given name from the group.
     *
     * @param type the type that "owns" the given StringTemplate group file. Dictates the filename of the
     *             StringTemplate group file on the classpath.
     * @param name the template name in the StringTemplate group.
     * @return the located SQL.
     */
    public static String findStringTemplateSql(Class type, String name) {
        StringTemplateGroup group = findStringTemplateGroup(type);

        if (!group.isDefined(name)) {
            throw new IllegalStateException("No StringTemplate group " + name + " for class " + type);
        }

        return group.getInstanceOf(name).getTemplate();
    }

    /**
     * Loads the StringTemplateGroup for the given type. Example: Given a type com.foo.Bar, returns a
     * StringTemplateGroup loaded from the resource named com/foo/Bar.sql.stg on the classpath.
     *
     * @param type the type that "owns" the given StringTemplate group file. Dictates the filename of the
     *             StringTemplate group file on the classpath.
     * @return the loaded StringTemplateGroup.
     */
    public static StringTemplateGroup findStringTemplateGroup(Class type) {
        return CACHE.get(type);
    }

    private static StringTemplateGroup readStringTemplateGroup(Class type) {
        String path = resourcePathFor(type);

        try (InputStream is = openStream(type.getClassLoader(), path)) {
            InputStreamReader reader = new InputStreamReader(is, UTF_8);
            return new StringTemplateGroup(reader);
        }
        catch (IOException e) {
            throw new RuntimeException("Unable to read StringTemplate group file at " + path + " on classpath", e);
        }
    }

    private static InputStream openStream(ClassLoader classLoader, String path) {
        InputStream is = classLoader.getResourceAsStream(path);

        if (is == null) {
            throw new IllegalStateException("Unable to find StringTemplate group file at " + path + " on classpath");
        }

        return is;
    }

    private static String resourcePathFor(Class clazz) {
        return clazz.getName().replace('.', '/') + TEMPLATE_GROUP_EXTENSION;
    }
}