/**
* Copyright OPS4J
*
* 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 org.ops4j.pax.wicket.util.serialization;
import java.io.Externalizable;
import java.io.IOException;
import java.io.NotSerializableException;
import java.io.ObjectOutput;
import java.io.ObjectOutputStream;
import java.io.ObjectStreamClass;
import java.io.ObjectStreamField;
import java.io.OutputStream;
import java.io.Serializable;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.Date;
import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.Map;
import java.util.Stack;
import org.apache.wicket.Component;
import org.apache.wicket.WicketRuntimeException;
import org.apache.wicket.util.lang.Generics;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* Utility class that analyzes objects for non-serializable nodes. Construct, then call {@link #check(Object)} with the
* object you want to check. When a non-serializable object is found, a {@link org.ops4j.pax.wicket.util.serialization.PaxWicketSerializableChecker.WicketNotSerializableException} is thrown
* with a message that shows the trace up to the not-serializable object. The exception is thrown for the first
* non-serializable instance it encounters, so multiple problems will not be shown.
* <p>
* As this class depends heavily on JDK's serialization internals using introspection, analyzing may not be possible,
* for instance when the runtime environment does not have sufficient rights to set fields accessible that would
* otherwise be hidden. You should call {@link org.ops4j.pax.wicket.util.serialization.PaxWicketSerializableChecker#isAvailable()} to see whether this class can
* operate properly. If it doesn't, you should fall back to e.g. re-throwing/ printing the
* {@link java.io.NotSerializableException} you probably got before using this class.
* </p>
*
* @author eelcohillenius
* @author Al Maw
* @version $Id: $Id
*/
public class PaxWicketSerializableChecker extends ObjectOutputStream
{
private static final Logger logger = LoggerFactory.getLogger(PaxWicketSerializableChecker.class);
/**
* Exception that is thrown when a non-serializable object was found.
*/
public static final class WicketNotSerializableException extends WicketRuntimeException
{
private static final long serialVersionUID = 1L;
WicketNotSerializableException(String message, Throwable cause)
{
super(message, cause);
}
}
/**
* Does absolutely nothing.
*/
private static class NoopOutputStream extends OutputStream
{
@Override
public void close()
{
}
@Override
public void flush()
{
}
@Override
public void write(byte[] b)
{
}
@Override
public void write(byte[] b, int i, int l)
{
}
@Override
public void write(int b)
{
}
}
private static abstract class ObjectOutputAdaptor implements ObjectOutput
{
@Override
public void close() throws IOException
{
}
@Override
public void flush() throws IOException
{
}
@Override
public void write(byte[] b) throws IOException
{
}
@Override
public void write(byte[] b, int off, int len) throws IOException
{
}
@Override
public void write(int b) throws IOException
{
}
@Override
public void writeBoolean(boolean v) throws IOException
{
}
@Override
public void writeByte(int v) throws IOException
{
}
@Override
public void writeBytes(String s) throws IOException
{
}
@Override
public void writeChar(int v) throws IOException
{
}
@Override
public void writeChars(String s) throws IOException
{
}
@Override
public void writeDouble(double v) throws IOException
{
}
@Override
public void writeFloat(float v) throws IOException
{
}
@Override
public void writeInt(int v) throws IOException
{
}
@Override
public void writeLong(long v) throws IOException
{
}
@Override
public void writeShort(int v) throws IOException
{
}
@Override
public void writeUTF(String str) throws IOException
{
}
}
/** Holds information about the field and the resulting object being traced. */
private static final class TraceSlot
{
private final String fieldDescription;
private final Object object;
TraceSlot(Object object, String fieldDescription)
{
super();
this.object = object;
this.fieldDescription = fieldDescription;
}
@Override
public String toString()
{
return object.getClass() + " - " + fieldDescription;
}
}
private static final NoopOutputStream DUMMY_OUTPUT_STREAM = new NoopOutputStream();
/** log. */
private static final Logger log = LoggerFactory.getLogger(PaxWicketSerializableChecker.class);
/** Whether we can execute the tests. If false, check will just return. */
private static boolean available = true;
// this hack - accessing the serialization API through introspection - is
// the only way to use Java serialization for our purposes without writing
// the whole thing from scratch (and even then, it would be limited). This
// way of working is of course fragile for internal API changes, but as we
// do an extra check on availability and we report when we can't use this
// introspection fu, we'll find out soon enough and clients on this class
// can fall back on Java's default exception for serialization errors (which
// sucks and is the main reason for this attempt).
private static Method LOOKUP_METHOD;
private static Method GET_CLASS_DATA_LAYOUT_METHOD;
private static Method GET_NUM_OBJ_FIELDS_METHOD;
private static Method GET_OBJ_FIELD_VALUES_METHOD;
private static Method GET_FIELD_METHOD;
private static Method HAS_WRITE_REPLACE_METHOD_METHOD;
private static Method INVOKE_WRITE_REPLACE_METHOD;
static
{
try
{
LOOKUP_METHOD = ObjectStreamClass.class.getDeclaredMethod("lookup", new Class[]{
Class.class, Boolean.TYPE });
LOOKUP_METHOD.setAccessible(true);
GET_CLASS_DATA_LAYOUT_METHOD = ObjectStreamClass.class.getDeclaredMethod(
"getClassDataLayout", (Class[]) null);
GET_CLASS_DATA_LAYOUT_METHOD.setAccessible(true);
GET_NUM_OBJ_FIELDS_METHOD = ObjectStreamClass.class.getDeclaredMethod(
"getNumObjFields", (Class[]) null);
GET_NUM_OBJ_FIELDS_METHOD.setAccessible(true);
GET_OBJ_FIELD_VALUES_METHOD = ObjectStreamClass.class.getDeclaredMethod(
"getObjFieldValues", new Class[]{ Object.class, Object[].class });
GET_OBJ_FIELD_VALUES_METHOD.setAccessible(true);
GET_FIELD_METHOD = ObjectStreamField.class.getDeclaredMethod("getField", (Class[]) null);
GET_FIELD_METHOD.setAccessible(true);
HAS_WRITE_REPLACE_METHOD_METHOD = ObjectStreamClass.class.getDeclaredMethod(
"hasWriteReplaceMethod", (Class[]) null);
HAS_WRITE_REPLACE_METHOD_METHOD.setAccessible(true);
INVOKE_WRITE_REPLACE_METHOD = ObjectStreamClass.class.getDeclaredMethod(
"invokeWriteReplace", new Class[]{ Object.class });
INVOKE_WRITE_REPLACE_METHOD.setAccessible(true);
} catch (Exception e)
{
logger.warn("SerializableChecker not available", e);
available = false;
}
}
/**
* Gets whether we can execute the tests. If false, calling {@link #check(Object)} will just return and you are
* advised to rely on the {@link java.io.NotSerializableException}. Clients are advised to call this method prior to calling
* the check method.
*
* @return whether security settings and underlying API etc allow for accessing the serialization API using
* introspection
*/
public static boolean isAvailable()
{
return available;
}
/** object stack that with the trace path. */
private final LinkedList<TraceSlot> traceStack = new LinkedList<TraceSlot>();
/** set for checking circular references. */
private final Map<Object, Object> checked = new IdentityHashMap<Object, Object>();
/** string stack with current names pushed. */
private final LinkedList<String> nameStack = new LinkedList<String>();
/** root object being analyzed. */
private Object root;
/** cache for classes - writeObject methods. */
private final Map<Class<?>, Object> writeObjectMethodCache = Generics.newHashMap();
/** current simple field name. */
private String simpleName = "";
/** current full field description. */
private String fieldDescription;
/** Exception that should be set as the cause when throwing a new exception. */
private final NotSerializableException exception;
private final Stack<Object> stack = new Stack<Object>();
/**
* Construct.
*
* @param exception exception that should be set as the cause when throwing a new exception
* @throws java.io.IOException cause
*/
public PaxWicketSerializableChecker(NotSerializableException exception) throws IOException
{
this.exception = exception;
}
/** {@inheritDoc} */
@Override
public void reset() throws IOException
{
root = null;
checked.clear();
fieldDescription = null;
simpleName = null;
traceStack.clear();
nameStack.clear();
writeObjectMethodCache.clear();
}
private void check(Object obj)
{
if (obj == null)
{
return;
}
try
{
if (stack.contains(obj))
{
return;
}
} catch (RuntimeException e)
{
log.warn("Wasn't possible to check the object " + obj.getClass() +
" possible due an problematic implementation of equals method");
/*
* Can't check if this obj were in stack, giving up because we don't want to throw an invaluable exception
* to user. The main goal of this checker is to find non serializable data
*/
return;
}
stack.push(obj);
try
{
internalCheck(obj);
} finally
{
stack.pop();
}
}
private void internalCheck(Object obj)
{
if (obj == null)
{
return;
}
Class<?> cls = obj.getClass();
nameStack.add(simpleName);
traceStack.add(new TraceSlot(obj, fieldDescription));
if (!(obj instanceof Serializable) && !Proxy.isProxyClass(cls) && validateAdditionalSerializableConditions(obj))
{
throw new WicketNotSerializableException(
toPrettyPrintedStack(obj.getClass().getName()), exception);
}
ObjectStreamClass desc;
for (;;)
{
try
{
desc = (ObjectStreamClass) LOOKUP_METHOD.invoke(null, new Object[]{ cls,
Boolean.TRUE });
Class<?> repCl;
if (!((Boolean) HAS_WRITE_REPLACE_METHOD_METHOD.invoke(desc, (Object[]) null)).booleanValue() ||
(obj = INVOKE_WRITE_REPLACE_METHOD.invoke(desc, new Object[]{ obj })) == null ||
(repCl = obj.getClass()) == cls)
{
break;
}
cls = repCl;
} catch (IllegalAccessException e)
{
throw new RuntimeException(e);
} catch (InvocationTargetException e)
{
throw new RuntimeException(e);
}
}
if (cls.isPrimitive())
{
// skip
}
else if (cls.isArray())
{
checked.put(obj, null);
Class<?> ccl = cls.getComponentType();
if (!ccl.isPrimitive())
{
Object[] objs = (Object[]) obj;
for (int i = 0; i < objs.length; i++)
{
String arrayPos = "[" + i + "]";
simpleName = arrayPos;
fieldDescription += arrayPos;
check(objs[i]);
}
}
}
else if (obj instanceof Externalizable && !Proxy.isProxyClass(cls))
{
Externalizable extObj = (Externalizable) obj;
try
{
extObj.writeExternal(new ObjectOutputAdaptor()
{
private int count = 0;
@Override
public void writeObject(Object streamObj) throws IOException
{
// Check for circular reference.
if (checked.containsKey(streamObj))
{
return;
}
checked.put(streamObj, null);
String arrayPos = "[write:" + count++ + "]";
simpleName = arrayPos;
fieldDescription += arrayPos;
check(streamObj);
}
});
} catch (Exception e)
{
if (e instanceof WicketNotSerializableException)
{
throw (WicketNotSerializableException) e;
}
log.warn("error delegating to Externalizable : " + e.getMessage() + ", path: " +
currentPath());
}
}
else
{
Method writeObjectMethod = null;
Object o = writeObjectMethodCache.get(cls);
if (o != null)
{
if (o instanceof Method)
{
writeObjectMethod = (Method) o;
}
}
else
{
try
{
writeObjectMethod = cls.getDeclaredMethod("writeObject",
new Class[]{ java.io.ObjectOutputStream.class });
writeObjectMethodCache.put(cls, writeObjectMethod);
} catch (SecurityException e)
{
// we can't access/ set accessible to true
writeObjectMethodCache.put(cls, Boolean.FALSE);
} catch (NoSuchMethodException e)
{
// cls doesn't have that method
writeObjectMethodCache.put(cls, Boolean.FALSE);
}
}
final Object original = obj;
if (writeObjectMethod != null)
{
class InterceptingObjectOutputStream extends ObjectOutputStream
{
private int counter;
InterceptingObjectOutputStream() throws IOException
{
super(DUMMY_OUTPUT_STREAM);
enableReplaceObject(true);
}
@Override
protected Object replaceObject(Object streamObj) throws IOException
{
if (streamObj == original)
{
return streamObj;
}
counter++;
// Check for circular reference.
if (checked.containsKey(streamObj))
{
return null;
}
streamObj = additionalObjectReplacements(streamObj);
checked.put(original, null);
String arrayPos = "[write:" + counter + "]";
simpleName = arrayPos;
fieldDescription += arrayPos;
check(streamObj);
return streamObj;
}
}
try
{
InterceptingObjectOutputStream ioos = new InterceptingObjectOutputStream();
ioos.writeObject(obj);
} catch (Exception e)
{
if (e instanceof WicketNotSerializableException)
{
throw (WicketNotSerializableException) e;
}
log.warn("error delegating to writeObject : " + e.getMessage() + ", path: " +
currentPath());
}
}
else
{
Object[] slots;
try
{
slots = (Object[]) GET_CLASS_DATA_LAYOUT_METHOD.invoke(desc, (Object[]) null);
} catch (Exception e)
{
throw new RuntimeException(e);
}
for (Object slot : slots) {
ObjectStreamClass slotDesc;
try
{
Field descField = slot.getClass().getDeclaredField("desc");
descField.setAccessible(true);
slotDesc = (ObjectStreamClass) descField.get(slot);
} catch (Exception e)
{
throw new RuntimeException(e);
}
checked.put(obj, null);
checkFields(obj, slotDesc);
}
}
}
traceStack.removeLast();
nameStack.removeLast();
}
private void checkFields(Object obj, ObjectStreamClass desc)
{
int numFields;
try
{
numFields = ((Integer) GET_NUM_OBJ_FIELDS_METHOD.invoke(desc, (Object[]) null)).intValue();
} catch (IllegalAccessException e)
{
throw new RuntimeException(e);
} catch (InvocationTargetException e)
{
throw new RuntimeException(e);
}
if (numFields > 0)
{
int numPrimFields;
ObjectStreamField[] fields = desc.getFields();
Object[] objVals = new Object[numFields];
numPrimFields = fields.length - objVals.length;
try
{
GET_OBJ_FIELD_VALUES_METHOD.invoke(desc, new Object[]{ obj, objVals });
} catch (IllegalAccessException e)
{
throw new RuntimeException(e);
} catch (InvocationTargetException e)
{
throw new RuntimeException(e);
}
for (int i = 0; i < objVals.length; i++)
{
if (objVals[i] instanceof String || objVals[i] instanceof Number ||
objVals[i] instanceof Date || objVals[i] instanceof Boolean ||
objVals[i] instanceof Class)
{
// filter out common cases
continue;
}
// Check for circular reference.
if (checked.containsKey(objVals[i]))
{
continue;
}
ObjectStreamField fieldDesc = fields[numPrimFields + i];
Field field;
try
{
field = (Field) GET_FIELD_METHOD.invoke(fieldDesc, (Object[]) null);
} catch (IllegalAccessException e)
{
throw new RuntimeException(e);
} catch (InvocationTargetException e)
{
throw new RuntimeException(e);
}
field.getName();
simpleName = field.getName();
fieldDescription = field.toString();
check(objVals[i]);
}
}
}
/**
* @return name from root to current node concatenated with slashes
*/
private StringBuffer currentPath()
{
StringBuffer b = new StringBuffer();
for (Iterator<String> it = nameStack.iterator(); it.hasNext();)
{
b.append(it.next());
if (it.hasNext())
{
b.append('/');
}
}
return b;
}
/**
* Dump with indentation.
*
* @param type the type that couldn't be serialized
* @return A very pretty dump
*/
private final String toPrettyPrintedStack(String type)
{
StringBuffer result = new StringBuffer();
StringBuffer spaces = new StringBuffer();
result.append("Unable to serialize class: ");
result.append(type);
result.append("\nField hierarchy is:");
for (Iterator<TraceSlot> i = traceStack.listIterator(); i.hasNext();)
{
spaces.append(" ");
TraceSlot slot = i.next();
result.append("\n").append(spaces).append(slot.fieldDescription);
result.append(" [class=").append(slot.object.getClass().getName());
if (slot.object instanceof Component)
{
Component component = (Component) slot.object;
result.append(", path=").append(component.getPath());
}
result.append("]");
}
result.append(" <----- field that is not serializable");
return result.toString();
}
/** {@inheritDoc} */
@Override
protected final void writeObjectOverride(Object obj) throws IOException
{
if (!available)
{
return;
}
root = obj;
if (fieldDescription == null)
{
fieldDescription = root instanceof Component ? ((Component) root).getPath() : "";
}
check(root);
}
/**
* Validates additional "isSerializable" conditions.
*
* @param obj a {@link java.lang.Object} object.
* @return is okay for serializable
*/
protected boolean validateAdditionalSerializableConditions(Object obj) {
return true;
}
/**
* Execute object replacement if required for a transformation.
*
* @param streamObj a {@link java.lang.Object} object.
* @return additional replacements
*/
protected Object additionalObjectReplacements(Object streamObj) {
return streamObj;
}
}