org.springframework.core.LocalVariableTableParameterNameDiscoverer Maven / Gradle / Ivy
/*
* Copyright 2002-2019 the original author or authors.
*
* 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
*
* https://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.springframework.core;
import java.io.IOException;
import java.io.InputStream;
import java.lang.reflect.Constructor;
import java.lang.reflect.Executable;
import java.lang.reflect.Method;
import java.util.Collections;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.springframework.asm.ClassReader;
import org.springframework.asm.ClassVisitor;
import org.springframework.asm.Label;
import org.springframework.asm.MethodVisitor;
import org.springframework.asm.Opcodes;
import org.springframework.asm.SpringAsmInfo;
import org.springframework.asm.Type;
import org.springframework.lang.Nullable;
import org.springframework.util.ClassUtils;
/**
* Implementation of {@link ParameterNameDiscoverer} that uses the LocalVariableTable
* information in the method attributes to discover parameter names. Returns
* {@code null} if the class file was compiled without debug information.
*
* Uses ObjectWeb's ASM library for analyzing class files. Each discoverer instance
* caches the ASM discovered information for each introspected Class, in a thread-safe
* manner. It is recommended to reuse ParameterNameDiscoverer instances as far as possible.
*
* @author Adrian Colyer
* @author Costin Leau
* @author Juergen Hoeller
* @author Chris Beams
* @author Sam Brannen
* @since 2.0
*/
public class LocalVariableTableParameterNameDiscoverer implements ParameterNameDiscoverer {
private static final Log logger = LogFactory.getLog(LocalVariableTableParameterNameDiscoverer.class);
// marker object for classes that do not have any debug info
private static final Map NO_DEBUG_INFO_MAP = Collections.emptyMap();
// the cache uses a nested index (value is a map) to keep the top level cache relatively small in size
private final Map, Map> parameterNamesCache = new ConcurrentHashMap<>(32);
@Override
@Nullable
public String[] getParameterNames(Method method) {
Method originalMethod = BridgeMethodResolver.findBridgedMethod(method);
return doGetParameterNames(originalMethod);
}
@Override
@Nullable
public String[] getParameterNames(Constructor ctor) {
return doGetParameterNames(ctor);
}
@Nullable
private String[] doGetParameterNames(Executable executable) {
Class declaringClass = executable.getDeclaringClass();
Map map = this.parameterNamesCache.computeIfAbsent(declaringClass, this::inspectClass);
return (map != NO_DEBUG_INFO_MAP ? map.get(executable) : null);
}
/**
* Inspects the target class.
* Exceptions will be logged, and a marker map returned to indicate the
* lack of debug information.
*/
private Map inspectClass(Class clazz) {
InputStream is = clazz.getResourceAsStream(ClassUtils.getClassFileName(clazz));
if (is == null) {
// We couldn't load the class file, which is not fatal as it
// simply means this method of discovering parameter names won't work.
if (logger.isDebugEnabled()) {
logger.debug("Cannot find '.class' file for class [" + clazz +
"] - unable to determine constructor/method parameter names");
}
return NO_DEBUG_INFO_MAP;
}
try {
ClassReader classReader = new ClassReader(is);
Map map = new ConcurrentHashMap<>(32);
classReader.accept(new ParameterNameDiscoveringVisitor(clazz, map), 0);
return map;
}
catch (IOException ex) {
if (logger.isDebugEnabled()) {
logger.debug("Exception thrown while reading '.class' file for class [" + clazz +
"] - unable to determine constructor/method parameter names", ex);
}
}
catch (IllegalArgumentException ex) {
if (logger.isDebugEnabled()) {
logger.debug("ASM ClassReader failed to parse class file [" + clazz +
"], probably due to a new Java class file version that isn't supported yet " +
"- unable to determine constructor/method parameter names", ex);
}
}
finally {
try {
is.close();
}
catch (IOException ex) {
// ignore
}
}
return NO_DEBUG_INFO_MAP;
}
/**
* Helper class that inspects all methods and constructors and then
* attempts to find the parameter names for the given {@link Executable}.
*/
private static class ParameterNameDiscoveringVisitor extends ClassVisitor {
private static final String STATIC_CLASS_INIT = "";
private final Class clazz;
private final Map executableMap;
public ParameterNameDiscoveringVisitor(Class clazz, Map executableMap) {
super(SpringAsmInfo.ASM_VERSION);
this.clazz = clazz;
this.executableMap = executableMap;
}
@Override
@Nullable
public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) {
// exclude synthetic + bridged && static class initialization
if (!isSyntheticOrBridged(access) && !STATIC_CLASS_INIT.equals(name)) {
return new LocalVariableTableVisitor(this.clazz, this.executableMap, name, desc, isStatic(access));
}
return null;
}
private static boolean isSyntheticOrBridged(int access) {
return (((access & Opcodes.ACC_SYNTHETIC) | (access & Opcodes.ACC_BRIDGE)) > 0);
}
private static boolean isStatic(int access) {
return ((access & Opcodes.ACC_STATIC) > 0);
}
}
private static class LocalVariableTableVisitor extends MethodVisitor {
private static final String CONSTRUCTOR = "";
private final Class clazz;
private final Map executableMap;
private final String name;
private final Type[] args;
private final String[] parameterNames;
private final boolean isStatic;
private boolean hasLvtInfo = false;
/*
* The nth entry contains the slot index of the LVT table entry holding the
* argument name for the nth parameter.
*/
private final int[] lvtSlotIndex;
public LocalVariableTableVisitor(Class clazz, Map map, String name, String desc, boolean isStatic) {
super(SpringAsmInfo.ASM_VERSION);
this.clazz = clazz;
this.executableMap = map;
this.name = name;
this.args = Type.getArgumentTypes(desc);
this.parameterNames = new String[this.args.length];
this.isStatic = isStatic;
this.lvtSlotIndex = computeLvtSlotIndices(isStatic, this.args);
}
@Override
public void visitLocalVariable(String name, String description, String signature, Label start, Label end, int index) {
this.hasLvtInfo = true;
for (int i = 0; i < this.lvtSlotIndex.length; i++) {
if (this.lvtSlotIndex[i] == index) {
this.parameterNames[i] = name;
}
}
}
@Override
public void visitEnd() {
if (this.hasLvtInfo || (this.isStatic && this.parameterNames.length == 0)) {
// visitLocalVariable will never be called for static no args methods
// which doesn't use any local variables.
// This means that hasLvtInfo could be false for that kind of methods
// even if the class has local variable info.
this.executableMap.put(resolveExecutable(), this.parameterNames);
}
}
private Executable resolveExecutable() {
ClassLoader loader = this.clazz.getClassLoader();
Class[] argTypes = new Class[this.args.length];
for (int i = 0; i < this.args.length; i++) {
argTypes[i] = ClassUtils.resolveClassName(this.args[i].getClassName(), loader);
}
try {
if (CONSTRUCTOR.equals(this.name)) {
return this.clazz.getDeclaredConstructor(argTypes);
}
return this.clazz.getDeclaredMethod(this.name, argTypes);
}
catch (NoSuchMethodException ex) {
throw new IllegalStateException("Method [" + this.name +
"] was discovered in the .class file but cannot be resolved in the class object", ex);
}
}
private static int[] computeLvtSlotIndices(boolean isStatic, Type[] paramTypes) {
int[] lvtIndex = new int[paramTypes.length];
int nextIndex = (isStatic ? 0 : 1);
for (int i = 0; i < paramTypes.length; i++) {
lvtIndex[i] = nextIndex;
if (isWideType(paramTypes[i])) {
nextIndex += 2;
}
else {
nextIndex++;
}
}
return lvtIndex;
}
private static boolean isWideType(Type aType) {
// float is not a wide type
return (aType == Type.LONG_TYPE || aType == Type.DOUBLE_TYPE);
}
}
}