mybatis / freemarker-scripting / #281

/*

 *    Copyright 2015-2022 the original author or authors.

 *

 *    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

 *

 *       https://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.mybatis.scripting.freemarker;

import java.io.CharArrayWriter;

import java.io.IOException;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.Map;

import org.apache.ibatis.builder.SqlSourceBuilder;

import org.apache.ibatis.mapping.BoundSql;

import org.apache.ibatis.mapping.SqlSource;

import org.apache.ibatis.session.Configuration;

import freemarker.template.Template;

import freemarker.template.TemplateException;

import freemarker.template.Version;

/**

 * Applies provided parameter(s) to FreeMarker template. Then passes the result into default MyBatis engine (and it

 * finally replaces #{}-params to '?'-params). So, FreeMarker is used as preprocessor for MyBatis engine.

 *

 * @author elwood

 */

public class FreeMarkerSqlSource implements SqlSource {

  private final Template template;

  private final Configuration configuration;

  private final Version incompatibleImprovementsVersion;

  public static final String GENERATED_PARAMS_KEY = "__GENERATED__";

  public FreeMarkerSqlSource(Template template, Configuration configuration, Version incompatibleImprovementsVersion) {

    this.template = template;

    this.configuration = configuration;

    this.incompatibleImprovementsVersion = incompatibleImprovementsVersion;

  }

  /**

   * Populates additional parameters to data context. Data context can be {@link java.util.Map} or

   * {@link org.mybatis.scripting.freemarker.ParamObjectAdapter} instance.

   */

  protected Object preProcessDataContext(Object dataContext, boolean isMap) {

    if (isMap) {

      ((Map<String, Object>) dataContext).put(MyBatisParamDirective.DEFAULT_KEY, new MyBatisParamDirective());

    } else {

      ((ParamObjectAdapter) dataContext).putAdditionalParam(MyBatisParamDirective.DEFAULT_KEY,

          new MyBatisParamDirective());

    }

    return dataContext;

  }

  @Override

  public BoundSql getBoundSql(Object parameterObject) {

    // Add to passed parameterObject our predefined directive - MyBatisParamDirective

    // It will be available as "p" inside templates

    Object dataContext;

    ArrayList generatedParams = new ArrayList<>();

    if (parameterObject != null) {

      if (parameterObject instanceof Map) {

        HashMap<String, Object> map = new HashMap<>((Map<String, Object>) parameterObject);

        map.put(GENERATED_PARAMS_KEY, generatedParams);

        dataContext = preProcessDataContext(map, true);

      } else {

        ParamObjectAdapter adapter = new ParamObjectAdapter(parameterObject, generatedParams,

            incompatibleImprovementsVersion);

        dataContext = preProcessDataContext(adapter, false);

      }

    } else {

      HashMap<Object, Object> map = new HashMap<>();

      map.put(GENERATED_PARAMS_KEY, generatedParams);

      dataContext = preProcessDataContext(map, true);

    }

    CharArrayWriter writer = new CharArrayWriter();

    try {

      template.process(dataContext, writer);

    } catch (TemplateException | IOException e) {

      throw new RuntimeException(e);

    }

    // We got SQL ready for MyBatis here. This SQL contains

    // params declarations like "#{param}",

    // they will be replaced to '?' by MyBatis engine further

    String sql = writer.toString();

    if (!generatedParams.isEmpty()) {

      if (!(parameterObject instanceof Map)) {

        throw new UnsupportedOperationException("Auto-generated prepared statements parameters"

            + " are not available if using parameters object. Use @Param-annotated parameters" + " instead.");

      }

      Map<String, Object> parametersMap = (Map<String, Object>) parameterObject;

      for (int i = 0; i < generatedParams.size(); i++) {

        parametersMap.put("_p" + i, generatedParams.get(i));

      }

    }

    // Pass retrieved SQL into MyBatis engine, it will substitute prepared-statements parameters

    SqlSourceBuilder sqlSourceParser = new SqlSourceBuilder(configuration);

    Class<?> parameterType1 = parameterObject == null ? Object.class : parameterObject.getClass();

    SqlSource sqlSource = sqlSourceParser.parse(sql, parameterType1, new HashMap<String, Object>());

    return sqlSource.getBoundSql(parameterObject);

  }

}