org.jolokia.service.serializer.json.BeanExtractor Maven / Gradle / Ivy
package org.jolokia.service.serializer.json;
import java.io.OutputStream;
import java.io.Writer;
import java.lang.reflect.*;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.*;
import javax.management.AttributeNotFoundException;
import org.jolokia.service.serializer.object.StringToObjectConverter;
import org.jolokia.server.core.service.serializer.ValueFaultHandler;
import org.jolokia.server.core.util.EscapeUtil;
import org.json.simple.JSONAware;
import org.json.simple.JSONObject;
/*
* Copyright 2009-2013 Roland Huss
*
* 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.
*/
/**
* Extractor for plain Java objects.
*
* @author roland
* @since Apr 19, 2009
*/
public class BeanExtractor implements Extractor {
private static final Set FINAL_CLASSES = new HashSet(Arrays.asList(
String.class,
Number.class,
Byte.class,
Double.class,
Float.class,
Long.class,
Short.class,
Integer.class,
Boolean.class
));
private static final Set IGNORE_METHODS = new HashSet(Arrays.asList(
"getClass",
// Ommit internal stuff
"getStackTrace",
"getClassLoader"
));
private static final Class[] IGNORED_RETURN_TYPES = new Class[]{
OutputStream.class,
Writer.class
};
private static final String[] GETTER_PREFIX = new String[]{"get", "is", "has"};
/** {@inheritDoc} */
public Class getType() {
return Object.class;
}
/** {@inheritDoc} */
@SuppressWarnings("PMD.CompareObjectsWithEquals")
public Object extractObject(ObjectToJsonConverter pConverter, Object pValue,
Stack pPathParts, boolean jsonify)
throws AttributeNotFoundException {
// Wrap fault handler if a wildcard path pattern is present
ValueFaultHandler faultHandler = pConverter.getValueFaultHandler();
String pathPart = pPathParts.isEmpty() ? null : pPathParts.pop();
if (pathPart != null) {
// Still some path elements available, so dive deeper
Object attributeValue = extractBeanPropertyValue(pValue, pathPart, faultHandler);
return pConverter.extractObject(attributeValue, pPathParts, jsonify);
} else {
if (jsonify) {
// We need the jsonfied value from here on.
return exctractJsonifiedValue(pConverter, pValue, pPathParts);
} else {
// No jsonification requested, hence we are returning the object itself
return pValue;
}
}
}
// Using standard set semantics
/** {@inheritDoc} */
public Object setObjectValue(StringToObjectConverter pConverter,Object pInner, String pAttribute, Object pValue)
throws IllegalAccessException, InvocationTargetException {
// Move this to plain object handler
String rest = new StringBuffer(pAttribute.substring(0,1).toUpperCase())
.append(pAttribute.substring(1)).toString();
String setter = new StringBuffer("set").append(rest).toString();
String getter = new StringBuffer("get").append(rest).toString();
Class clazz = pInner.getClass();
Method found = null;
for (Method method : clazz.getMethods()) {
if (method.getName().equals(setter)) {
found = method;
break;
}
}
if (found == null) {
throw new IllegalArgumentException(
"No Method " + setter + " known for object of type " + clazz.getName());
}
Class params[] = found.getParameterTypes();
if (params.length != 1) {
throw new IllegalArgumentException(
"Invalid parameter signature for " + setter + " known for object of type "
+ clazz.getName() + ". Setter must take exactly one parameter.");
}
Object oldValue;
try {
final Method getMethod = clazz.getMethod(getter);
AccessController.doPrivileged(new SetMethodAccessibleAction(getMethod));
oldValue = getMethod.invoke(pInner);
} catch (NoSuchMethodException exp) {
// Ignored, we simply dont return an old value
oldValue = null;
}
AccessController.doPrivileged(new SetMethodAccessibleAction(found));
found.invoke(pInner,pConverter.deserialize(params[0].getName(), pValue));
return oldValue;
}
/** {@inheritDoc} */
public boolean canSetValue() {
return true;
}
// =====================================================================================================
private Object exctractJsonifiedValue(ObjectToJsonConverter pConverter, Object pValue, Stack pPathParts)
throws AttributeNotFoundException {
if (pValue.getClass().isPrimitive() || FINAL_CLASSES.contains(pValue.getClass()) || pValue instanceof JSONAware) {
// No further diving, use these directly
return pValue;
} else {
// For the rest we build up a JSON map with the attributes as keys and the value are
List attributes = extractBeanAttributes(pValue);
if (attributes != null && attributes.size() > 0) {
return extractBeanValues(pConverter, pValue, pPathParts, attributes);
} else {
// No further attributes, return string representation
return pValue.toString();
}
}
}
private Object extractBeanValues(ObjectToJsonConverter pConverter, Object pValue, Stack pPathParts, List pAttributes) throws AttributeNotFoundException {
Map ret = new JSONObject();
for (String attribute : pAttributes) {
Stack path = (Stack) pPathParts.clone();
try {
ret.put(attribute, extractJsonifiedPropertyValue(pConverter, pValue, attribute, path));
} catch (ValueFaultHandler.AttributeFilteredException exp) {
// Skip it since we are doing a path with wildcards, filtering out non-matchin attrs.
}
}
if (ret.isEmpty() && pAttributes.size() > 0) {
// Ok, everything was filtered. Bubbling upwards ...
throw new ValueFaultHandler.AttributeFilteredException();
}
return ret;
}
@SuppressWarnings("PMD.CompareObjectsWithEquals")
private Object extractJsonifiedPropertyValue(ObjectToJsonConverter pConverter, Object pValue, String pAttribute, Stack pPathParts)
throws AttributeNotFoundException {
ValueFaultHandler faultHandler = pConverter.getValueFaultHandler();
Object value = extractBeanPropertyValue(pValue, pAttribute, faultHandler);
if (value == null) {
if (!pPathParts.isEmpty()) {
faultHandler.handleException(new AttributeNotFoundException(
"Cannot apply remaining path " + EscapeUtil.combineToPath(pPathParts) + " on value null"));
}
return null;
} else if (value == pValue) {
if (!pPathParts.isEmpty()) {
faultHandler.handleException(new AttributeNotFoundException(
"Cannot apply remaining path " + EscapeUtil.combineToPath(pPathParts) + " on a cycle"));
}
// Break Cycle
return "[this]";
} else {
// Call into the converted recursively for any object known.
return pConverter.extractObject(value, pPathParts, true /* jsonify */);
}
}
// Extract all attributes from a given bean
private List extractBeanAttributes(Object pValue) {
List attrs = new ArrayList();
for (Method method : pValue.getClass().getMethods()) {
if (!Modifier.isStatic(method.getModifiers()) &&
!IGNORE_METHODS.contains(method.getName()) &&
!isIgnoredType(method.getReturnType())) {
addAttributes(attrs, method);
}
}
return attrs;
}
// Add attributes, which are taken from get methods to the given list
@SuppressWarnings("PMD.UnnecessaryCaseChange")
private void addAttributes(List pAttrs, Method pMethod) {
String name = pMethod.getName();
for (String pref : GETTER_PREFIX) {
if (name.startsWith(pref) && name.length() > pref.length()
&& pMethod.getParameterTypes().length == 0) {
int len = pref.length();
String firstLetter = name.substring(len,len+1);
// Only for getter compliant to the beans conventions (first letter after prefix is upper case)
if (firstLetter.toUpperCase().equals(firstLetter)) {
String attribute =
new StringBuffer(firstLetter.toLowerCase()).
append(name.substring(len+1)).toString();
pAttrs.add(attribute);
}
}
}
}
private Object extractBeanPropertyValue(Object pValue, String pAttribute, ValueFaultHandler pFaultHandler)
throws AttributeNotFoundException {
Class clazz = pValue.getClass();
Method method = null;
String suffix = new StringBuilder(pAttribute.substring(0,1).toUpperCase()).append(pAttribute.substring(1)).toString();
for (String pref : GETTER_PREFIX) {
try {
String methodName = new StringBuilder(pref).append(suffix).toString();
method = clazz.getMethod(methodName);
} catch (NoSuchMethodException e) {
// Try next one
continue;
}
// We found a valid method
break;
}
// Finally, try the attribute name directly
if (method == null) {
try {
method = clazz.getMethod(new StringBuilder(pAttribute.substring(0,1).toLowerCase())
.append(pAttribute.substring(1)).toString());
} catch (NoSuchMethodException exp) {
method = null;
}
}
if (method == null) {
return pFaultHandler.handleException(new AttributeNotFoundException(
"No getter known for attribute " + pAttribute + " for class " + pValue.getClass().getName()));
}
try {
method.setAccessible(true);
return method.invoke(pValue);
} catch (IllegalAccessException e) {
return pFaultHandler.handleException(new IllegalStateException("Error while extracting " + pAttribute
+ " from " + pValue,e));
} catch (InvocationTargetException e) {
return pFaultHandler.handleException(new IllegalStateException("Error while extracting " + pAttribute
+ " from " + pValue,e));
}
}
/**
* Privileged action for setting the accesibility mode for a method to true
*/
private static class SetMethodAccessibleAction implements PrivilegedAction {
private final Method getMethod;
/**
* Which method to set accessible
*
* @param pMethod method to set accessible
*/
public SetMethodAccessibleAction(Method pMethod) {
getMethod = pMethod;
}
/** {@inheritDoc} */
public Void run() {
getMethod.setAccessible(true);
return null;
}
}
// Ignore certain return types, since their getter tend to have bad
// side effects like nuking files etc. See Jetty FileResource.getOutputStream() as a bad example
// This method is not necessarily cheap (since it called quite often), however necessary
// as safety net. I messed up my complete local Maven repository only be serializing a Jetty ServletContext
private boolean isIgnoredType(Class pReturnType) {
for (Class type : IGNORED_RETURN_TYPES) {
if (type.isAssignableFrom(pReturnType)) {
return true;
}
}
return false;
}
}
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