Mailing-List: contact dev-help@drill.apache.org; run by ezmlm
Precedence: bulk
Reply-To: dev@drill.apache.org
From: paul-rogers <git@git.apache.org>
To: dev@drill.apache.org
Reply-To: dev@drill.apache.org
References: <git-pr-660-drill@git.apache.org>
In-Reply-To: <git-pr-660-drill@git.apache.org>
Subject: [GitHub] drill pull request #660: DRILL-5052: Option to debug generated Java code usi...
Content-Type: text/plain
Message-Id: <20161209043600.14AC3F2134@git1-us-west.apache.org>
Date: Fri,  9 Dec 2016 04:35:59 +0000 (UTC)
archived-at: Fri, 09 Dec 2016 04:36:05 -0000

Github user paul-rogers commented on a diff in the pull request:

    https://github.com/apache/drill/pull/660#discussion_r91633759
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/compile/ClassBuilder.java ---
    @@ -0,0 +1,190 @@
    +/**
    + * 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 org.apache.drill.exec.compile;
    +
    +import java.io.File;
    +import java.io.FileWriter;
    +import java.io.IOException;
    +import java.util.Map;
    +
    +import org.apache.drill.common.config.DrillConfig;
    +import org.apache.drill.exec.compile.ClassTransformer.ClassNames;
    +import org.apache.drill.exec.exception.ClassTransformationException;
    +import org.apache.drill.exec.expr.CodeGenerator;
    +import org.apache.drill.exec.server.options.OptionManager;
    +import org.codehaus.commons.compiler.CompileException;
    +
    +/**
    + * Implements the "plain-old Java" method of code generation and
    + * compilation. Given a {@link CodeGenerator}, obtains the generated
    + * source code, compiles it with the selected compiler, loads the
    + * byte-codes into a class loader and provides the resulting
    + * class. Compared with the {@link ClassTransformer} mechanism,
    + * this one requires the code generator to have generated a complete
    + * Java class that is capable of direct compilation and loading.
    + * This means the generated class must be a subclass of the template
    + * so that the JVM can use normal Java inheritance to associate the
    + * template and generated methods.
    + * <p>
    + * Here is how to use the plain-old Java technique to debug
    + * generated code:
    + * <ul>
    + * <li>Set the config option <var>drill.exec.compile.save_source</var>
    + * to <var>true</var>.</li>
    + * <li>Set the config option <var>drill.exec.compile.code_dir</var>
    + * to the location where you want to save the generated source
    + * code.</li>
    + * <li>Where you generate code (using a {@link CodeGenerator}),
    + * set the "plain-old Java" options:<pre>
    + * CodeGenerator&lt;Foo> cg = ...
    + * cg.plainOldJavaCapable(true); // Class supports plain-old Java
    + * cg.preferPlainOldJava(true); // Actually generate plain-old Java
    + * ...</pre></li>
    + * <li>In your favorite IDE, add to the code lookup path the
    + * code directory saved earlier. In Eclipse, for example, you do
    + * this in the debug configuration you will use to debug Drill.</li>
    + * <li>Set a breakpoint in template used for the generated code.</li>
    + * <li>Run Drill. The IDE will stop at your breakpoint.</li>
    + * <li>Step into the generated code. Examine class field and
    + * local variables. Have fun!</li>
    + * </ul>
    + * <p>
    + * Note: not all generated code is ready to be compiled as plain-old
    + * Java. Some classes omit from the template the proper <code>throws</code>
    + * declarations. Other minor problems may also crop up. All are easy
    + * to fix. Once you've done so, add the following to mark that you've
    + * done the clean-up:<pre>
    + * cg.plainOldJavaCapable(true); // Class supports plain-old Java</pre>
    + * <p>
    + * The setting to prefer plain-old Java is ignored for generated
    + * classes not marked as plain-old Java capable.
    + */
    +
    +public class ClassBuilder {
    +
    +  public static final String SAVE_CODE_OPTION = CodeCompiler.COMPILE_BASE + ".save_source";
    +  public static final String CODE_DIR_OPTION = CodeCompiler.COMPILE_BASE + ".code_dir";
    +
    +  private final DrillConfig config;
    +  private final OptionManager options;
    +  private final boolean saveCode;
    +  private final File codeDir;
    +
    +  public ClassBuilder(DrillConfig config, OptionManager optionManager) {
    +    this.config = config;
    +    options = optionManager;
    +
    +    // The option to save code is a boot-time option because
    +    // it is used selectively during debugging, but can cause
    +    // excessive I/O in a running server if used to save all code.
    +
    +    saveCode = config.getBoolean( SAVE_CODE_OPTION );
    +    codeDir = new File( config.getString( CODE_DIR_OPTION ) );
    +  }
    +
    +  /**
    +   * Given a code generator which has already generated plain-old Java
    +   * code, compile the code, create a class loader, and return the
    +   * resulting Java class.
    +   *
    +   * @param cg a plain-old Java capable code generator that has generated
    +   * plain-old Java code
    +   * @return the class that the code generator defines
    +   * @throws ClassTransformationException
    +   */
    +
    +  public Class<?> getImplementationClass(CodeGenerator<?> cg) throws ClassTransformationException {
    +    try {
    +      return compileClass( cg );
    +    } catch (CompileException | ClassNotFoundException e) {
    +      throw new ClassTransformationException(e);
    +    } catch (IOException e) {
    +      throw new ClassTransformationException(e);
    +    }
    +  }
    +
    +  /**
    +   * Performs the actual work of compiling the code and loading the class.
    +   *
    +   * @param cg
    +   * @return
    +   * @throws IOException
    +   * @throws CompileException
    +   * @throws ClassNotFoundException
    +   * @throws ClassTransformationException
    +   */
    --- End diff --
    
    Done.


---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastructure@apache.org or file a JIRA ticket
with INFRA.
---