com.github.ibole.microservice.common.utils.ClassHelper Maven / Gradle / Ivy
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package com.github.ibole.microservice.common.utils;
import java.lang.reflect.Array;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import javassist.ClassPool;
import javassist.CtClass;
import javassist.CtMethod;
import javassist.bytecode.CodeAttribute;
import javassist.bytecode.LocalVariableAttribute;
import javassist.bytecode.MethodInfo;
public class ClassHelper {
/**
* Get method variable names for the provided method.
*
* @param classname String
* @param methodname String
* @return the String[] of method variable name.
*/
public static String[] getMethodVariableName(String classname, String methodname) {
try {
ClassPool pool = ClassPool.getDefault();
CtClass cc = pool.get(classname);
CtMethod cm = cc.getDeclaredMethod(methodname);
MethodInfo methodInfo = cm.getMethodInfo();
CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
String[] paramNames = new String[cm.getParameterTypes().length];
LocalVariableAttribute attr =
(LocalVariableAttribute) codeAttribute.getAttribute(LocalVariableAttribute.tag);
if (attr != null) {
int pos = Modifier.isStatic(cm.getModifiers()) ? 0 : 1;
for (int i = 0; i < paramNames.length; i++) {
paramNames[i] = attr.variableName(i + pos);
}
return paramNames;
}
} catch (Exception e) {
throw new RuntimeException(e);
}
return null;
}
public static Class forNameWithThreadContextClassLoader(String name)
throws ClassNotFoundException {
return forName(name, Thread.currentThread().getContextClassLoader());
}
public static Class forNameWithCallerClassLoader(String name, Class caller)
throws ClassNotFoundException {
return forName(name, caller.getClassLoader());
}
public static ClassLoader getCallerClassLoader(Class caller) {
return caller.getClassLoader();
}
/**
* get class loader.
*
* @param cls Class
* @return class loader ClassLoader
*/
public static ClassLoader getClassLoader(Class cls) {
ClassLoader cl = null;
try {
cl = Thread.currentThread().getContextClassLoader();
} catch (Throwable ex) {
// Cannot access thread context ClassLoader - falling back to system class loader...
}
if (cl == null) {
// No thread context class loader -> use class loader of this class.
cl = cls.getClassLoader();
}
return cl;
}
/**
* Return the default ClassLoader to use: typically the thread context ClassLoader, if available;
* the ClassLoader that loaded the ClassUtils class will be used as fallback.
*
* Call this method if you intend to use the thread context ClassLoader in a scenario where you
* absolutely need a non-null ClassLoader reference: for example, for class path resource loading
* (but not necessarily for Class.forName, which accepts a null
* ClassLoader reference as well).
*
* @return the default ClassLoader (never null)
* @see java.lang.Thread#getContextClassLoader()
*/
public static ClassLoader getClassLoader() {
return getClassLoader(ClassHelper.class);
}
/**
* Same as Class.forName(), except that it works for primitive types.
* @param name String
* @return class instance Class
*/
public static Class forName(String name) throws ClassNotFoundException {
return forName(name, getClassLoader());
}
/**
* Replacement for Class.forName() that also returns Class instances for primitives
* (like "int") and array class names (like "String[]").
*
* @param name the name of the Class
* @param classLoader the class loader to use (may be null, which indicates the
* default class loader)
* @return Class instance for the supplied name
* @throws ClassNotFoundException if the class was not found
* @throws LinkageError if the class file could not be loaded
* @see Class#forName(String, boolean, ClassLoader)
*/
public static Class forName(String name, ClassLoader classLoader)
throws ClassNotFoundException, LinkageError {
Class clazz = resolvePrimitiveClassName(name);
if (clazz != null) {
return clazz;
}
// "java.lang.String[]" style arrays
if (name.endsWith(ARRAY_SUFFIX)) {
String elementClassName = name.substring(0, name.length() - ARRAY_SUFFIX.length());
Class elementClass = forName(elementClassName, classLoader);
return Array.newInstance(elementClass, 0).getClass();
}
// "[Ljava.lang.String;" style arrays
int internalArrayMarker = name.indexOf(INTERNAL_ARRAY_PREFIX);
if (internalArrayMarker != -1 && name.endsWith(";")) {
String elementClassName = null;
if (internalArrayMarker == 0) {
elementClassName = name.substring(INTERNAL_ARRAY_PREFIX.length(), name.length() - 1);
} else if (name.startsWith("[")) {
elementClassName = name.substring(1);
}
Class elementClass = forName(elementClassName, classLoader);
return Array.newInstance(elementClass, 0).getClass();
}
ClassLoader classLoaderToUse = classLoader;
if (classLoaderToUse == null) {
classLoaderToUse = getClassLoader();
}
return classLoaderToUse.loadClass(name);
}
/**
* Resolve the given class name as primitive class, if appropriate, according to the JVM's naming
* rules for primitive classes.
*
* Also supports the JVM's internal class names for primitive arrays. Does not support the
* "[]" suffix notation for primitive arrays; this is only supported by {@link #forName}.
*
* @param name the name of the potentially primitive class
* @return the primitive class, or null if the name does not denote a primitive class
* or primitive array class
*/
public static Class resolvePrimitiveClassName(String name) {
Class result = null;
// Most class names will be quite long, considering that they
// SHOULD sit in a package, so a length check is worthwhile.
if (name != null && name.length() <= 8) {
// Could be a primitive - likely.
result = (Class) primitiveTypeNameMap.get(name);
}
return result;
}
/** Suffix for array class names: "[]" */
public static final String ARRAY_SUFFIX = "[]";
/** Prefix for internal array class names: "[L" */
private static final String INTERNAL_ARRAY_PREFIX = "[L";
/**
* Map with primitive type name as key and corresponding primitive type as value, for example:
* "int" -> "int.class".
*/
private static final Map> primitiveTypeNameMap =
new HashMap>(16);
/**
* Map with primitive wrapper type as key and corresponding primitive type as value, for example:
* Integer.class -> int.class.
*/
private static final Map, Class> primitiveWrapperTypeMap =
new HashMap, Class>(8);
static {
primitiveWrapperTypeMap.put(Boolean.class, boolean.class);
primitiveWrapperTypeMap.put(Byte.class, byte.class);
primitiveWrapperTypeMap.put(Character.class, char.class);
primitiveWrapperTypeMap.put(Double.class, double.class);
primitiveWrapperTypeMap.put(Float.class, float.class);
primitiveWrapperTypeMap.put(Integer.class, int.class);
primitiveWrapperTypeMap.put(Long.class, long.class);
primitiveWrapperTypeMap.put(Short.class, short.class);
Set> primitiveTypeNames = new HashSet>(16);
primitiveTypeNames.addAll(primitiveWrapperTypeMap.values());
primitiveTypeNames.addAll(Arrays.asList(new Class[] {boolean[].class, byte[].class,
char[].class, double[].class, float[].class, int[].class, long[].class, short[].class}));
for (Iterator> it = primitiveTypeNames.iterator(); it.hasNext();) {
Class primitiveClass = (Class) it.next();
primitiveTypeNameMap.put(primitiveClass.getName(), primitiveClass);
}
}
public static String toShortString(Object obj) {
if (obj == null) {
return "null";
}
return obj.getClass().getSimpleName() + "@" + System.identityHashCode(obj);
}
}