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Java example source code file (LineNumbers.java)

This example Java source code file (LineNumbers.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

annotationvisitor, class, constructor, integer, ioexception, label, linenumberannotationvisitor, linenumbermethodvisitor, linenumberreader, linenumbers, member, object, reflection, string, stringbuilder, util

The LineNumbers.java Java example source code

/**
 * Copyright (C) 2006 Google Inc.
 *
 * 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 com.google.inject.internal.util;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.base.Preconditions;
import com.google.common.collect.Maps;

import org.objectweb.asm.AnnotationVisitor;
import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.FieldVisitor;
import org.objectweb.asm.Label;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;

import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.util.Map;

/**
 * Looks up line numbers for classes and their members.
 *
 * @author Chris Nokleberg
 */
final class LineNumbers {

  private final Class type;
  private final Map<String, Integer> lines = Maps.newHashMap();
  private String source;
  private int firstLine = Integer.MAX_VALUE;

  /**
   * Reads line number information from the given class, if available.
   *
   * @param type the class to read line number information from
   * @throws IllegalArgumentException if the bytecode for the class cannot be found
   * @throws java.io.IOException if an error occurs while reading bytecode
   */
  public LineNumbers(Class type) throws IOException {
    this.type = type;

    if (!type.isArray()) {
      InputStream in = type.getResourceAsStream("/" + type.getName().replace('.', '/') + ".class");
      if (in != null) {
        try {
          new ClassReader(in).accept(new LineNumberReader(), ClassReader.SKIP_FRAMES);
        } finally {
          try {
            in.close();
          } catch (IOException ignored) {}
        }
      }
    }
  }

  /**
   * Get the source file name as read from the bytecode.
   *
   * @return the source file name if available, or null
   */
  public String getSource() {
    return source;
  }

  /**
   * Get the line number associated with the given member.
   *
   * @param member a field, constructor, or method belonging to the class used during construction
   * @return the wrapped line number, or null if not available
   * @throws IllegalArgumentException if the member does not belong to the class used during
   * construction
   */
  public Integer getLineNumber(Member member) {
    Preconditions.checkArgument(type == member.getDeclaringClass(),
        "Member %s belongs to %s, not %s", member, member.getDeclaringClass(), type);
    return lines.get(memberKey(member));
  }

  /** Gets the first line number. */
  public int getFirstLine() {
    return firstLine == Integer.MAX_VALUE ? 1 : firstLine;
  }

  private String memberKey(Member member) {
    checkNotNull(member, "member");

    /*if[AOP]*/
    if (member instanceof Field) {
      return member.getName();

    } else if (member instanceof Method) {
      return member.getName() + org.objectweb.asm.Type.getMethodDescriptor((Method) member);

    } else if (member instanceof Constructor) {
      StringBuilder sb = new StringBuilder().append("<init>(");
      for (Class param : ((Constructor) member).getParameterTypes()) {
          sb.append(org.objectweb.asm.Type.getDescriptor(param));
      }
      return sb.append(")V").toString();

    } else {
      throw new IllegalArgumentException(
          "Unsupported implementation class for Member, " + member.getClass());
    }
    /*end[AOP]*/
    /*if[NO_AOP]
    return "<NO_MEMBER_KEY>";
    end[NO_AOP]*/
  }  

  private class LineNumberReader extends ClassVisitor {

    private int line = -1;
    private String pendingMethod;
    private String name;

    LineNumberReader() {
      super(Opcodes.ASM5);
    }

    public void visit(int version, int access, String name, String signature,
        String superName, String[] interfaces) {
      this.name = name;
    }

    public MethodVisitor visitMethod(int access, String name, String desc,
        String signature, String[] exceptions) {
      if ((access & Opcodes.ACC_PRIVATE) != 0) {
        return null;
      }
      pendingMethod = name + desc;
      line = -1;
      return new LineNumberMethodVisitor();
    }

    public void visitSource(String source, String debug) {
      LineNumbers.this.source = source;
    }

    public void visitLineNumber(int line, Label start) {
      if (line < firstLine) {
        firstLine = line;
      }

      this.line = line;
      if (pendingMethod != null) {
        lines.put(pendingMethod, line);
        pendingMethod = null;
      }
    }

    public FieldVisitor visitField(int access, String name, String desc,
        String signature, Object value) {
      return null;
    }

    public AnnotationVisitor visitAnnotation(String desc, boolean visible) {
      return new LineNumberAnnotationVisitor();
    }

    public AnnotationVisitor visitParameterAnnotation(int parameter,
        String desc, boolean visible) {
      return new LineNumberAnnotationVisitor();
    }

    class LineNumberMethodVisitor extends MethodVisitor {
      LineNumberMethodVisitor() {
        super(Opcodes.ASM5);
      }

      public AnnotationVisitor visitAnnotation(String desc, boolean visible) {
        return new LineNumberAnnotationVisitor();
      }

      public AnnotationVisitor visitAnnotationDefault() {
        return new LineNumberAnnotationVisitor();
      }

      public void visitFieldInsn(int opcode, String owner, String name,
          String desc) {
        if (opcode == Opcodes.PUTFIELD && LineNumberReader.this.name.equals(owner)
            && !lines.containsKey(name) && line != -1) {
          lines.put(name, line);
        }
      }

      public void visitLineNumber(int line, Label start) {
        LineNumberReader.this.visitLineNumber(line, start);
      }
    }

    class LineNumberAnnotationVisitor extends AnnotationVisitor {
      LineNumberAnnotationVisitor() {
        super(Opcodes.ASM5);
      }
      public AnnotationVisitor visitAnnotation(String name, String desc) {
        return this;
      }
      public AnnotationVisitor visitArray(String name) {
        return this;
      }
      public void visitLocalVariable(String name, String desc, String signature,
          Label start, Label end, int index) {
      }

    }

  }
}

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