aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorManuel Carrasco Moñino <manuel.carrasco.m@gmail.com>2013-02-07 12:45:43 +0100
committerManuel Carrasco Moñino <manuel.carrasco.m@gmail.com>2013-02-07 12:45:43 +0100
commit9276a33e0c9c9444050c1958012c989cc933bacf (patch)
treecc71bcad707872eeb7abc49b98946635d5aedaf9
parentf390606d5c942bd338cc348b84e9da6803cb8026 (diff)
downloadgwtquery-9276a33e0c9c9444050c1958012c989cc933bacf.tar.gz
gwtquery-9276a33e0c9c9444050c1958012c989cc933bacf.zip
Preparing archetype to deploy the release 1.3.1 to central repos
Diffstat
-rw-r--r--archetype/pom.xml8
1 files changed, 4 insertions, 4 deletions
diff --git a/archetype/pom.xml b/archetype/pom.xml
index 32443b7a..914179a5 100644
--- a/archetype/pom.xml
+++ b/archetype/pom.xml
@@ -4,7 +4,7 @@
<modelVersion>4.0.0</modelVersion>
<groupId>com.googlecode.gwtquery</groupId>
<artifactId>gquery-archetype</artifactId>
- <version>1.3.1</version>
+ <version>1.3.1-SNAPSHOT</version>
<packaging>maven-archetype</packaging>
<name>GwtQuery Archetype</name>
@@ -17,9 +17,9 @@
<description>This archetype generates a Gwt-2.5.0-rc1 project with all set to use GwtQuery and its plugins.</description>
<scm>
- <connection>scm:svn:http://gwtquery.googlecode.com/svn/trunk/archetype</connection>
- <developerConnection>scm:svn:https://gwtquery.googlecode.com/svn/trunk/archetype</developerConnection>
- <url>http://code.google.com/p/gwtquery/source/browse/trunk/archetype</url>
+ <connection>scm:git:https://code.google.com/p/gwtquery/</connection>
+ <developerConnection>scm:git:git@github.com:gwtquery/gwtquery.git</developerConnection>
+ <url>http://code.google.com/p/gwtquery/source/browse/</url>
</scm>
<developers>
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-22 16:49:03 +0000
='n162' href='#n162'>162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 
<html>
<head>
   <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
   <title>Javassist Tutorial</title>
   <link rel="stylesheet" type="text/css" href="brown.css">
</head>

<body>

<div align="right">Getting Started with Javassist</div>

<div align="left"><a href="tutorial2.html">Previous page</a></div>

<p>
<a href="#intro">5. Bytecode level API</a>
<ul>
<li><a href="#classfile">Obtaining a <code>ClassFile</code> object</a>
<br><li><a href="#member">Adding and removing a member</a>
<br><li><a href="#traverse">Traversing a method body</a>
<br><li><a href="#bytecode">Producing a bytecode sequence</a>
<br><li><a href="#annotation">Annotations (Meta tags)</a>

</ul>

<p><a href="#generics">6. Generics</a>

<p><a href="#j2me">7. J2ME</a>

<p><br>

<a name="intro">
<h2>5. Bytecode level API</h2>

<p>
Javassist also provides lower-level API for directly editing
a class file.  To use this level of API, you need detailed
knowledge of the Java bytecode and the class file format
while this level of API allows you any kind of modification
of class files.

<p>
If you want to just produce a simple class file,
<code>javassist.bytecode.ClassFileWriter</code> might provide
the best API for you.  It is much faster than
<code>javassist.bytecode.ClassFile</code> although its API
is minimum.

<a name="classfile">
<h3>5.1 Obtaining a <code>ClassFile</code> object</h3>

<p>A <code>javassist.bytecode.ClassFile</code> object represents
a class file.  To obtian this object, <code>getClassFile()</code>
in <code>CtClass</code> should be called.

<p>Otherwise, you can construct a
<code>javassist.bytecode.ClassFile</code> directly from a class file.
For example,

<ul><pre>
BufferedInputStream fin
    = new BufferedInputStream(new FileInputStream("Point.class"));
ClassFile cf = new ClassFile(new DataInputStream(fin));
</pre></ul>

<p>
This code snippet creats a <code>ClassFile</code> object from
<code>Point.class</code>.

<p>
A <code>ClassFile</code> object can be written back to a
class file.  <code>write()</code> in <code>ClassFile</code>
writes the contents of the class file to a given
<code>DataOutputStream</code>.

<p><br>

<a name="member">
<h3>5.2 Adding and removing a member</h3>

<p>
<code>ClassFile</code> provides <code>addField()</code> and
<code>addMethod()</code> for adding a field or a method (note that
a constructor is regarded as a method at the bytecode level).
It also provides <code>addAttribute()</code> for adding an attribute
to the class file.

<p>
Note that <code>FieldInfo</code>, <code>MethodInfo</code>, and
<code>AttributeInfo</code> objects include a link to a
<code>ConstPool</code> (constant pool table) object.  The <code>ConstPool</code>
object must be common to the <code>ClassFile</code> object and
a <code>FieldInfo</code> (or <code>MethodInfo</code> etc.) object
that is added to that <code>ClassFile</code> object.
In other words, a <code>FieldInfo</code> (or <code>MethodInfo</code> etc.) object
must not be shared among different <code>ClassFile</code> objects.

<p>
To remove a field or a method from a <code>ClassFile</code> object,
you must first obtain a <code>java.util.List</code>
object containing all the fields of the class.  <code>getFields()</code>
and <code>getMethods()</code> return the lists.  A field or a method can
be removed by calling <code>remove()</code> on the <code>List</code> object.
An attribute can be removed in a similar way.
Call <code>getAttributes()</code> in <code>FieldInfo</code> or
<code>MethodInfo</code> to obtain the list of attributes,
and remove one from the list.


<p><br>

<a name="traverse">
<h3>5.3 Traversing a method body</h3>

<p>
To examine every bytecode instruction in a method body,
<code>CodeIterator</code> is useful.  To otbain this object,
do as follows:

<ul><pre>
ClassFile cf = ... ;
MethodInfo minfo = cf.getMethod("move");    // we assume move is not overloaded.
CodeAttribute ca = minfo.getCodeAttribute();
CodeIterator i = ca.iterator();
</pre></ul>

<p>
A <code>CodeIterator</code> object allows you to visit every
bytecode instruction one by one from the beginning to the end.
The following methods are part of the methods declared in
<code>CodeIterator</code>:

<ul>
<li><code>void begin()</code><br>
Move to the first instruction.<br>
<li><code>void move(int index)</code><br>
Move to the instruction specified by the given index.<br>
<li><code>boolean hasNext()</code><br>
Returns true if there is more instructions.<br>
<li><code>int next()</code><br>
Returns the index of the next instruction.<br>
<em>Note that it does not return the opcode of the next
instruction.</em><br>
<li><code>int byteAt(int index)</code><br>
Returns the unsigned 8bit value at the index.<br>
<li><code>int u16bitAt(int index)</code><br>
Returns the unsigned 16bit value at the index.<br>
<li><code>int write(byte[] code, int index)</code><br>
Writes a byte array at the index.<br>
<li><code>void insert(int index, byte[] code)</code><br>
Inserts a byte array at the index.
Branch offsets etc. are automatically adjusted.<br>
</ul>

<p>The following code snippet displays all the instructions included
in a method body:

<ul><pre>
CodeIterator ci = ... ;
while (ci.hasNext()) {
    int index = ci.next();
    int op = ci.byteAt(index);
    System.out.println(Mnemonic.OPCODE[op]);
}
</pre></ul>

<p><br>

<a name="bytecode">
<h3>5.4 Producing a bytecode sequence</h3>

<p>
A <code>Bytecode</code> object represents a sequence of bytecode
instructions.  It is a growable array of bytecode.
Here is a sample code snippet:

<ul><pre>
ConstPool cp = ...;    // constant pool table
Bytecode b = new Bytecode(cp, 1, 0);
b.addIconst(3);
b.addReturn(CtClass.intType);
CodeAttribute ca = b.toCodeAttribute();
</pre></ul>

<p>
This produces the code attribute representing the following sequence:

<ul><pre>
iconst_3
ireturn
</pre></ul>

<p>
You can also obtain a byte array containing this sequence by
calling <code>get()</code> in <code>Bytecode</code>.  The
obtained array can be inserted in another code attribute.

<p>
While <code>Bytecode</code> provides a number of methods for adding a
specific instruction to the sequence, it provides
<code>addOpcode()</code> for adding an 8bit opcode and
<code>addIndex()</code> for adding an index.
The 8bit value of each opcode is defined in the <code>Opcode</code>
interface.

<p>
<code>addOpcode()</code> and other methods for adding a specific
instruction are automatically maintain the maximum stack depth
unless the control flow does not include a branch.
This value can be obtained by calling <code>getMaxStack()</code>
on the <code>Bytecode</code> object.
It is also reflected on the <code>CodeAttribute</code> object
constructed from the <code>Bytecode</code> object.
To recompute the maximum stack depth of a method body,
call <code>computeMaxStack()</code> in <code>CodeAttribute</code>.

<p><br>

<a name="annotation">
<h3>5.5 Annotations (Meta tags)</h3>

<p>Annotations are stored in a class file
as runtime invisible (or visible) annotations attribute.
These attributes can be obtained from <code>ClassFile</code>,
<code>MethodInfo</code>, or <code>FieldInfo</code> objects.
Call <code>getAttribute(AnnotationsAttribute.invisibleTag)</code>
on those objects.  For more details, see the javadoc manual
of <code>javassist.bytecode.AnnotationsAttribute</code> class
and the <code>javassist.bytecode.annotation</code> package.

<p>Javassist also let you access annotations by the higher-level
API.
If you want to access annotations through <code>CtClass</code>,
call <code>getAnnotations()</code> in <code>CtClass</code> or
<code>CtBehavior</code>.

<p><br>

<h2><a name="generics">6. Generics</a></h2>

<p>The lower-level API of Javassist fully supports generics
introduced by Java 5.  On the other hand, the higher-level
API such as <code>CtClass</code> does not directly support
generics.  However, this is not a serious problem for bytecode
transformation.

<p>The generics of Java is implemented by the erasure technique.
After compilation, all type parameters are dropped off.  For
example, suppose that your source code declares a parameterized
type <code>Vector&lt;String&gt;</code>:

<ul><pre>
Vector&lt;String&gt; v = new Vector&lt;String&gt();
  :
String s = v.get(0);
</pre></ul>

<p>The compiled bytecode is equivalent to the following code:

<ul><pre>
Vector v = new Vector();
  :
String s = (String)v.get(0);
</pre></ul>

<p>So when you write a bytecode transformer, you can just drop
off all type parameters.  For example, if you have a class:

<ul><pre>
public class Wrapper&lt;T&gt; {
  T value;
  public Wrapper(T t) { value = t; }
}
</pre></ul>

<p>and want to add an interface <code>Getter&lt;T&gt;</code> to the
class <code>Wrapper&lt;T&gt;</code>:

<ul><pre>
public interface Getter&lt;T&gt; {
  T get();
}
</pre></ul>

<p>Then the interface you really have to add is <code>Getter</code>
(the type parameters <code>&lt;T&gt;</code> drops off)
and the method you also have to add to the <code>Wrapper</code>
class is this simple one:

<ul><pre>
public Object get() { return value; }
</pre></ul>

<p>Note that no type parameters are necessary.

<p><br>

<h2><a name="j2me">7. J2ME</a></h2>

<p>If you modify a class file for the J2ME execution environment,
you must perform <it>preverification</it>.  Preverifying is basically
producing stack maps, which is similar to stack map tables introduced
into J2SE at JDK 1.6.  Javassist maintains the stack maps for J2ME only if
<code>javassist.bytecode.MethodInfo.doPreverify</code> is true.

<p>You can also manually
produce a stack map for a modified method.
For a given method represented by a <code>CtMethod</code> object <code>m</code>,
you can produce a stack map by calling the following methods:

<ul><pre>
m.getMethodInfo().rebuildStackMapForME(cpool);
</pre></ul>

<p>Here, <code>cpool</code> is a <code>ClassPool</code> object, which is
available by calling <code>getClassPool()</code> on a <code>CtClass</code>
object.  A <code>ClassPool</code> object is responsible for finding
class files from given class pathes.  To obtain all the <code>CtMethod</code>
objects, call the <code>getDeclaredMethods</code> method on a <code>CtClass</code> object.

<p><br>

<a href="tutorial2.html">Previous page</a>

<hr>
Java(TM) is a trademark of Sun Microsystems, Inc.<br>
Copyright (C) 2000-2007 by Shigeru Chiba, All rights reserved.
</body>
</html>