级别: 中级

package com.sosnoski.dwct;

public enum Primitive
{
    BOOLEAN, BYTE, CHARACTER, DOUBLE, FLOAT, INT, LONG, SHORT;
    
    public static void main(String[] args) {
        for (Primitive p : Primitive.values()) {
            int size = -1;
            switch (p) {
                case BOOLEAN:
                case BYTE:
                    size = 1;
                    break;
                case CHARACTER:
                case SHORT:
                    size = 2;
                    break;
                case FLOAT:
                case INT:
                    size = 4;
                    break;
                case DOUBLE:
                case LONG:
                    size = 8;
                    break;
            }
            System.out.println(p + " is size " + size);
        }
    }
}

[dennis@notebook code]$ java -cp classes com.sosnoski.dwct.Primitive
BOOLEAN is size 1
BYTE is size 1
CHARACTER is size 2
DOUBLE is size 8
FLOAT is size 4
INT is size 4
LONG is size 8
SHORT is size 2

[dennis@notebook code]$ java -cp retro/release/retroweaver.jar:retro/lib/bcel-5.1.jar:retro/lib/
  jace.jar:retro/lib/Regex.jar com.rc.retroweaver.Weaver -source classes
[RetroWeaver] Weaving /home/dennis/writing/articles/devworks/series/may05/code/
  classes/com/sosnoski/dwct/Primitive$1.class
[RetroWeaver] Weaving /home/dennis/writing/articles/devworks/series/may05/code/
  classes/com/sosnoski/dwct/Primitive.class

package com.sosnoski.asm;

import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Method;
import java.net.URL;
import java.net.URLClassLoader;

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassWriter;

public class ToStringLoader extends URLClassLoader
{
    private ToStringLoader(URL[] urls, ClassLoader parent) {
        super(urls, parent);
    }

    // override of ClassLoader method
    protected Class findClass(String name) throws ClassNotFoundException {
        String resname = name.replace('.', '/') + ".class";
        InputStream is = getResourceAsStream(resname);
        if (is == null) {
            System.err.println("Unable to load class " + name +
                " for annotation checking");
            return super.findClass(name);
        } else {
            System.out.println("Processing class " + name);
            try {
                
                // read the entire content into byte array
                ByteArrayOutputStream bos = new ByteArrayOutputStream();
                byte[] buff = new byte[1024];
                int length;
                while ((length = is.read(buff)) >= 0) {
                    bos.write(buff, 0, length);
                }
                byte[] bytes = bos.toByteArray();
                
                // scan class binary format to find fields for toString() method
                ClassReader creader = new ClassReader(bytes);
                FieldCollector visitor = new FieldCollector();
                creader.accept(visitor, true);
                FieldInfo[] fields = visitor.getFields();
                if (fields.length > 0) {
                    
                    // annotated fields present, generate the toString() method
                    System.out.println("Modifying " + name);
                    ClassWriter writer = new ClassWriter(false);
                    ToStringGenerator gen = new ToStringGenerator(writer,
                            name.replace('.', '/'), fields);
                    creader.accept(gen, false);
                    bytes = writer.toByteArray();
                }
                
                // return the (possibly modified) class
                return defineClass(bytes, 0, bytes.length);
                
            } catch (IOException e) {
                throw new ClassNotFoundException("Error reading class " + name);
            }
        }
    }

    public static void main(String[] args) {
        if (args.length >= 1) {
            try {
                
                // get paths to be used for loading
                ClassLoader base = ClassLoader.getSystemClassLoader();
                URL[] urls;
                if (base instanceof URLClassLoader) {
                    urls = ((URLClassLoader)base).getURLs();
                } else {
                    urls = new URL[] { new File(".").toURI().toURL() };
                }
                
                // load the target class using custom class loader
                ToStringLoader loader =
                    new ToStringLoader(urls, base.getParent());
                Class clas = loader.loadClass(args[0]);
                    
                // invoke the "main" method of the application class
                Class[] ptypes = new Class[] { args.getClass() };
                Method main = clas.getDeclaredMethod("main", ptypes);
                String[] pargs = new String[args.length-1];
                System.arraycopy(args, 1, pargs, 0, pargs.length);
                Thread.currentThread().setContextClassLoader(loader);
                main.invoke(null, new Object[] { pargs });
                
            } catch (Exception e) {
                e.printStackTrace();
            }
            
        } else {
            System.out.println("Usage: com.sosnoski.asm.ToStringLoader " +
                "report-class main-class args...");
        }
    }
}

[dennis@notebook code]$ java -cp classes:retro/release/retroweaver-rt.jar:lib/
  asm-2.0.RC1.jar:lib/asm-commons-2.0.RC1.jar
  com.sosnoski.asm.ToStringLoader com.sosnoski.dwct.Run
Processing class com.sosnoski.dwct.Run
Processing class com.sosnoski.dwct.Name
Modifying com.sosnoski.dwct.Name
Processing class com.sosnoski.dwct.Address
Modifying com.sosnoski.dwct.Address
Processing class com.sosnoski.dwct.Customer
Modifying com.sosnoski.dwct.Customer
Customer: #=12345
 Name: Dennis Michael Sosnoski
 Address: street=1234 5th St. city=Redmond state=WA zip=98052
 homePhone=425 555-1212 dayPhone=425 555-1213