001/* 002 * Copyright 2002-2019 the original author or authors. 003 * 004 * Licensed under the Apache License, Version 2.0 (the "License"); 005 * you may not use this file except in compliance with the License. 006 * You may obtain a copy of the License at 007 * 008 * https://www.apache.org/licenses/LICENSE-2.0 009 * 010 * Unless required by applicable law or agreed to in writing, software 011 * distributed under the License is distributed on an "AS IS" BASIS, 012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 013 * See the License for the specific language governing permissions and 014 * limitations under the License. 015 */ 016 017package org.springframework.core; 018 019import java.io.IOException; 020import java.io.InputStream; 021import java.lang.reflect.Constructor; 022import java.lang.reflect.Executable; 023import java.lang.reflect.Method; 024import java.util.Collections; 025import java.util.Map; 026import java.util.concurrent.ConcurrentHashMap; 027 028import org.apache.commons.logging.Log; 029import org.apache.commons.logging.LogFactory; 030 031import org.springframework.asm.ClassReader; 032import org.springframework.asm.ClassVisitor; 033import org.springframework.asm.Label; 034import org.springframework.asm.MethodVisitor; 035import org.springframework.asm.Opcodes; 036import org.springframework.asm.SpringAsmInfo; 037import org.springframework.asm.Type; 038import org.springframework.lang.Nullable; 039import org.springframework.util.ClassUtils; 040 041/** 042 * Implementation of {@link ParameterNameDiscoverer} that uses the LocalVariableTable 043 * information in the method attributes to discover parameter names. Returns 044 * {@code null} if the class file was compiled without debug information. 045 * 046 * <p>Uses ObjectWeb's ASM library for analyzing class files. Each discoverer instance 047 * caches the ASM discovered information for each introspected Class, in a thread-safe 048 * manner. It is recommended to reuse ParameterNameDiscoverer instances as far as possible. 049 * 050 * @author Adrian Colyer 051 * @author Costin Leau 052 * @author Juergen Hoeller 053 * @author Chris Beams 054 * @author Sam Brannen 055 * @since 2.0 056 */ 057public class LocalVariableTableParameterNameDiscoverer implements ParameterNameDiscoverer { 058 059 private static final Log logger = LogFactory.getLog(LocalVariableTableParameterNameDiscoverer.class); 060 061 // marker object for classes that do not have any debug info 062 private static final Map<Executable, String[]> NO_DEBUG_INFO_MAP = Collections.emptyMap(); 063 064 // the cache uses a nested index (value is a map) to keep the top level cache relatively small in size 065 private final Map<Class<?>, Map<Executable, String[]>> parameterNamesCache = new ConcurrentHashMap<>(32); 066 067 068 @Override 069 @Nullable 070 public String[] getParameterNames(Method method) { 071 Method originalMethod = BridgeMethodResolver.findBridgedMethod(method); 072 return doGetParameterNames(originalMethod); 073 } 074 075 @Override 076 @Nullable 077 public String[] getParameterNames(Constructor<?> ctor) { 078 return doGetParameterNames(ctor); 079 } 080 081 @Nullable 082 private String[] doGetParameterNames(Executable executable) { 083 Class<?> declaringClass = executable.getDeclaringClass(); 084 Map<Executable, String[]> map = this.parameterNamesCache.computeIfAbsent(declaringClass, this::inspectClass); 085 return (map != NO_DEBUG_INFO_MAP ? map.get(executable) : null); 086 } 087 088 /** 089 * Inspects the target class. 090 * <p>Exceptions will be logged, and a marker map returned to indicate the 091 * lack of debug information. 092 */ 093 private Map<Executable, String[]> inspectClass(Class<?> clazz) { 094 InputStream is = clazz.getResourceAsStream(ClassUtils.getClassFileName(clazz)); 095 if (is == null) { 096 // We couldn't load the class file, which is not fatal as it 097 // simply means this method of discovering parameter names won't work. 098 if (logger.isDebugEnabled()) { 099 logger.debug("Cannot find '.class' file for class [" + clazz + 100 "] - unable to determine constructor/method parameter names"); 101 } 102 return NO_DEBUG_INFO_MAP; 103 } 104 try { 105 ClassReader classReader = new ClassReader(is); 106 Map<Executable, String[]> map = new ConcurrentHashMap<>(32); 107 classReader.accept(new ParameterNameDiscoveringVisitor(clazz, map), 0); 108 return map; 109 } 110 catch (IOException ex) { 111 if (logger.isDebugEnabled()) { 112 logger.debug("Exception thrown while reading '.class' file for class [" + clazz + 113 "] - unable to determine constructor/method parameter names", ex); 114 } 115 } 116 catch (IllegalArgumentException ex) { 117 if (logger.isDebugEnabled()) { 118 logger.debug("ASM ClassReader failed to parse class file [" + clazz + 119 "], probably due to a new Java class file version that isn't supported yet " + 120 "- unable to determine constructor/method parameter names", ex); 121 } 122 } 123 finally { 124 try { 125 is.close(); 126 } 127 catch (IOException ex) { 128 // ignore 129 } 130 } 131 return NO_DEBUG_INFO_MAP; 132 } 133 134 135 /** 136 * Helper class that inspects all methods and constructors and then 137 * attempts to find the parameter names for the given {@link Executable}. 138 */ 139 private static class ParameterNameDiscoveringVisitor extends ClassVisitor { 140 141 private static final String STATIC_CLASS_INIT = "<clinit>"; 142 143 private final Class<?> clazz; 144 145 private final Map<Executable, String[]> executableMap; 146 147 public ParameterNameDiscoveringVisitor(Class<?> clazz, Map<Executable, String[]> executableMap) { 148 super(SpringAsmInfo.ASM_VERSION); 149 this.clazz = clazz; 150 this.executableMap = executableMap; 151 } 152 153 @Override 154 @Nullable 155 public MethodVisitor visitMethod(int access, String name, String desc, String signature, String[] exceptions) { 156 // exclude synthetic + bridged && static class initialization 157 if (!isSyntheticOrBridged(access) && !STATIC_CLASS_INIT.equals(name)) { 158 return new LocalVariableTableVisitor(this.clazz, this.executableMap, name, desc, isStatic(access)); 159 } 160 return null; 161 } 162 163 private static boolean isSyntheticOrBridged(int access) { 164 return (((access & Opcodes.ACC_SYNTHETIC) | (access & Opcodes.ACC_BRIDGE)) > 0); 165 } 166 167 private static boolean isStatic(int access) { 168 return ((access & Opcodes.ACC_STATIC) > 0); 169 } 170 } 171 172 173 private static class LocalVariableTableVisitor extends MethodVisitor { 174 175 private static final String CONSTRUCTOR = "<init>"; 176 177 private final Class<?> clazz; 178 179 private final Map<Executable, String[]> executableMap; 180 181 private final String name; 182 183 private final Type[] args; 184 185 private final String[] parameterNames; 186 187 private final boolean isStatic; 188 189 private boolean hasLvtInfo = false; 190 191 /* 192 * The nth entry contains the slot index of the LVT table entry holding the 193 * argument name for the nth parameter. 194 */ 195 private final int[] lvtSlotIndex; 196 197 public LocalVariableTableVisitor(Class<?> clazz, Map<Executable, String[]> map, String name, String desc, boolean isStatic) { 198 super(SpringAsmInfo.ASM_VERSION); 199 this.clazz = clazz; 200 this.executableMap = map; 201 this.name = name; 202 this.args = Type.getArgumentTypes(desc); 203 this.parameterNames = new String[this.args.length]; 204 this.isStatic = isStatic; 205 this.lvtSlotIndex = computeLvtSlotIndices(isStatic, this.args); 206 } 207 208 @Override 209 public void visitLocalVariable(String name, String description, String signature, Label start, Label end, int index) { 210 this.hasLvtInfo = true; 211 for (int i = 0; i < this.lvtSlotIndex.length; i++) { 212 if (this.lvtSlotIndex[i] == index) { 213 this.parameterNames[i] = name; 214 } 215 } 216 } 217 218 @Override 219 public void visitEnd() { 220 if (this.hasLvtInfo || (this.isStatic && this.parameterNames.length == 0)) { 221 // visitLocalVariable will never be called for static no args methods 222 // which doesn't use any local variables. 223 // This means that hasLvtInfo could be false for that kind of methods 224 // even if the class has local variable info. 225 this.executableMap.put(resolveExecutable(), this.parameterNames); 226 } 227 } 228 229 private Executable resolveExecutable() { 230 ClassLoader loader = this.clazz.getClassLoader(); 231 Class<?>[] argTypes = new Class<?>[this.args.length]; 232 for (int i = 0; i < this.args.length; i++) { 233 argTypes[i] = ClassUtils.resolveClassName(this.args[i].getClassName(), loader); 234 } 235 try { 236 if (CONSTRUCTOR.equals(this.name)) { 237 return this.clazz.getDeclaredConstructor(argTypes); 238 } 239 return this.clazz.getDeclaredMethod(this.name, argTypes); 240 } 241 catch (NoSuchMethodException ex) { 242 throw new IllegalStateException("Method [" + this.name + 243 "] was discovered in the .class file but cannot be resolved in the class object", ex); 244 } 245 } 246 247 private static int[] computeLvtSlotIndices(boolean isStatic, Type[] paramTypes) { 248 int[] lvtIndex = new int[paramTypes.length]; 249 int nextIndex = (isStatic ? 0 : 1); 250 for (int i = 0; i < paramTypes.length; i++) { 251 lvtIndex[i] = nextIndex; 252 if (isWideType(paramTypes[i])) { 253 nextIndex += 2; 254 } 255 else { 256 nextIndex++; 257 } 258 } 259 return lvtIndex; 260 } 261 262 private static boolean isWideType(Type aType) { 263 // float is not a wide type 264 return (aType == Type.LONG_TYPE || aType == Type.DOUBLE_TYPE); 265 } 266 } 267 268}