一、前言

关于alibaba的dubbo源码包com.alibaba.dubbo.common.compiler.support.ClassUtils类工具类，实现对基本类型/对象类的实例化、基本类型boxed转换包装类及包装类unboxed转基本类型、获取getGenericClass指定接口泛型类型、获取getMethodName指定方法、查找指定方法类型searchMethod等方法处理，详情参见源码说明。

二、源码说明

package com.alibaba.dubbo.common.compiler.support;@b@@b@import java.io.PrintWriter;@b@import java.io.StringWriter;@b@import java.lang.reflect.Array;@b@import java.lang.reflect.GenericArrayType;@b@import java.lang.reflect.Method;@b@import java.lang.reflect.Modifier;@b@import java.lang.reflect.ParameterizedType;@b@import java.net.URI;@b@import java.net.URISyntaxException;@b@import java.util.Collection;@b@import java.util.HashMap;@b@import java.util.Map;@b@@b@/**@b@ * ClassUtils. (Tool, Static, ThreadSafe)@b@ */@b@public class ClassUtils {@b@@b@    public static final String CLASS_EXTENSION = ".class";@b@@b@    public static final String JAVA_EXTENSION = ".java";@b@    private static final int JIT_LIMIT = 5 * 1024;@b@@b@    private ClassUtils() {@b@    }@b@@b@    public static Object newInstance(String name) {@b@        try {@b@            return forName(name).newInstance();@b@        } catch (InstantiationException e) {@b@            throw new IllegalStateException(e.getMessage(), e);@b@        } catch (IllegalAccessException e) {@b@            throw new IllegalStateException(e.getMessage(), e);@b@        }@b@    }@b@@b@    public static Class<?> forName(String[] packages, String className) {@b@        try {@b@            return _forName(className);@b@        } catch (ClassNotFoundException e) {@b@            if (packages != null && packages.length > 0) {@b@                for (String pkg : packages) {@b@                    try {@b@                        return _forName(pkg + "." + className);@b@                    } catch (ClassNotFoundException e2) {@b@                    }@b@                }@b@            }@b@            throw new IllegalStateException(e.getMessage(), e);@b@        }@b@    }@b@@b@    public static Class<?> forName(String className) {@b@        try {@b@            return _forName(className);@b@        } catch (ClassNotFoundException e) {@b@            throw new IllegalStateException(e.getMessage(), e);@b@        }@b@    }@b@@b@    public static Class<?> _forName(String className) throws ClassNotFoundException {@b@        if ("boolean".equals(className))@b@            return boolean.class;@b@        if ("byte".equals(className))@b@            return byte.class;@b@        if ("char".equals(className))@b@            return char.class;@b@        if ("short".equals(className))@b@            return short.class;@b@        if ("int".equals(className))@b@            return int.class;@b@        if ("long".equals(className))@b@            return long.class;@b@        if ("float".equals(className))@b@            return float.class;@b@        if ("double".equals(className))@b@            return double.class;@b@        if ("boolean[]".equals(className))@b@            return boolean[].class;@b@        if ("byte[]".equals(className))@b@            return byte[].class;@b@        if ("char[]".equals(className))@b@            return char[].class;@b@        if ("short[]".equals(className))@b@            return short[].class;@b@        if ("int[]".equals(className))@b@            return int[].class;@b@        if ("long[]".equals(className))@b@            return long[].class;@b@        if ("float[]".equals(className))@b@            return float[].class;@b@        if ("double[]".equals(className))@b@            return double[].class;@b@        try {@b@            return arrayForName(className);@b@        } catch (ClassNotFoundException e) {@b@            // try to load from java.lang package@b@            if (className.indexOf('.') == -1) {@b@                try {@b@                    return arrayForName("java.lang." + className);@b@                } catch (ClassNotFoundException e2) {@b@                    // ignore, let the original exception be thrown@b@                }@b@            }@b@            throw e;@b@        }@b@    }@b@@b@    private static Class<?> arrayForName(String className) throws ClassNotFoundException {@b@        return Class.forName(className.endsWith("[]")@b@                ? "[L" + className.substring(0, className.length() - 2) + ";"@b@                : className, true, Thread.currentThread().getContextClassLoader());@b@    }@b@@b@    public static Class<?> getBoxedClass(Class<?> type) {@b@        if (type == boolean.class) {@b@            return Boolean.class;@b@        } else if (type == char.class) {@b@            return Character.class;@b@        } else if (type == byte.class) {@b@            return Byte.class;@b@        } else if (type == short.class) {@b@            return Short.class;@b@        } else if (type == int.class) {@b@            return Integer.class;@b@        } else if (type == long.class) {@b@            return Long.class;@b@        } else if (type == float.class) {@b@            return Float.class;@b@        } else if (type == double.class) {@b@            return Double.class;@b@        } else {@b@            return type;@b@        }@b@    }@b@@b@    public static Boolean boxed(boolean v) {@b@        return Boolean.valueOf(v);@b@    }@b@@b@    public static Character boxed(char v) {@b@        return Character.valueOf(v);@b@    }@b@@b@    public static Byte boxed(byte v) {@b@        return Byte.valueOf(v);@b@    }@b@@b@    public static Short boxed(short v) {@b@        return Short.valueOf(v);@b@    }@b@@b@    public static Integer boxed(int v) {@b@        return Integer.valueOf(v);@b@    }@b@@b@    public static Long boxed(long v) {@b@        return Long.valueOf(v);@b@    }@b@@b@    public static Float boxed(float v) {@b@        return Float.valueOf(v);@b@    }@b@@b@    public static Double boxed(double v) {@b@        return Double.valueOf(v);@b@    }@b@@b@    public static Object boxed(Object v) {@b@        return v;@b@    }@b@@b@    public static boolean unboxed(Boolean v) {@b@        return v == null ? false : v.booleanValue();@b@    }@b@@b@    public static char unboxed(Character v) {@b@        return v == null ? '\0' : v.charValue();@b@    }@b@@b@    public static byte unboxed(Byte v) {@b@        return v == null ? 0 : v.byteValue();@b@    }@b@@b@    public static short unboxed(Short v) {@b@        return v == null ? 0 : v.shortValue();@b@    }@b@@b@    public static int unboxed(Integer v) {@b@        return v == null ? 0 : v.intValue();@b@    }@b@@b@    public static long unboxed(Long v) {@b@        return v == null ? 0 : v.longValue();@b@    }@b@@b@    public static float unboxed(Float v) {@b@        return v == null ? 0 : v.floatValue();@b@    }@b@@b@    public static double unboxed(Double v) {@b@        return v == null ? 0 : v.doubleValue();@b@    }@b@@b@    public static Object unboxed(Object v) {@b@        return v;@b@    }@b@@b@    public static boolean isNotEmpty(Object object) {@b@        return getSize(object) > 0;@b@    }@b@@b@    public static int getSize(Object object) {@b@        if (object == null) {@b@            return 0;@b@        }@b@        if (object instanceof Collection<?>) {@b@            return ((Collection<?>) object).size();@b@        } else if (object instanceof Map<?, ?>) {@b@            return ((Map<?, ?>) object).size();@b@        } else if (object.getClass().isArray()) {@b@            return Array.getLength(object);@b@        } else {@b@            return -1;@b@        }@b@    }@b@@b@    public static URI toURI(String name) {@b@        try {@b@            return new URI(name);@b@        } catch (URISyntaxException e) {@b@            throw new RuntimeException(e);@b@        }@b@    }@b@@b@    public static Class<?> getGenericClass(Class<?> cls) {@b@        return getGenericClass(cls, 0);@b@    }@b@@b@    public static Class<?> getGenericClass(Class<?> cls, int i) {@b@        try {@b@            ParameterizedType parameterizedType = ((ParameterizedType) cls.getGenericInterfaces()[0]);@b@            Object genericClass = parameterizedType.getActualTypeArguments()[i];@b@            if (genericClass instanceof ParameterizedType) {@b@                return (Class<?>) ((ParameterizedType) genericClass).getRawType();@b@            } else if (genericClass instanceof GenericArrayType) {@b@                return (Class<?>) ((GenericArrayType) genericClass).getGenericComponentType();@b@            } else if (genericClass != null) {@b@                return (Class<?>) genericClass;@b@            }@b@        } catch (Throwable e) {@b@        }@b@        if (cls.getSuperclass() != null) {@b@            return getGenericClass(cls.getSuperclass(), i);@b@        } else {@b@            throw new IllegalArgumentException(cls.getName() + " generic type undefined!");@b@        }@b@    }@b@@b@    public static boolean isBeforeJava5(String javaVersion) {@b@        return (javaVersion == null || javaVersion.length() == 0 || "1.0".equals(javaVersion)@b@                || "1.1".equals(javaVersion) || "1.2".equals(javaVersion)@b@                || "1.3".equals(javaVersion) || "1.4".equals(javaVersion));@b@    }@b@@b@    public static boolean isBeforeJava6(String javaVersion) {@b@        return isBeforeJava5(javaVersion) || "1.5".equals(javaVersion);@b@    }@b@@b@    public static String toString(Throwable e) {@b@        StringWriter w = new StringWriter();@b@        PrintWriter p = new PrintWriter(w);@b@        p.print(e.getClass().getName() + ": ");@b@        if (e.getMessage() != null) {@b@            p.print(e.getMessage() + "\n");@b@        }@b@        p.println();@b@        try {@b@            e.printStackTrace(p);@b@            return w.toString();@b@        } finally {@b@            p.close();@b@        }@b@    }@b@@b@    public static void checkBytecode(String name, byte[] bytecode) {@b@        if (bytecode.length > JIT_LIMIT) {@b@            System.err.println("The template bytecode too long, may be affect the JIT compiler. template class: " + name);@b@        }@b@    }@b@@b@    public static String getSizeMethod(Class<?> cls) {@b@        try {@b@            return cls.getMethod("size", new Class<?>[0]).getName() + "()";@b@        } catch (NoSuchMethodException e) {@b@            try {@b@                return cls.getMethod("length", new Class<?>[0]).getName() + "()";@b@            } catch (NoSuchMethodException e2) {@b@                try {@b@                    return cls.getMethod("getSize", new Class<?>[0]).getName() + "()";@b@                } catch (NoSuchMethodException e3) {@b@                    try {@b@                        return cls.getMethod("getLength", new Class<?>[0]).getName() + "()";@b@                    } catch (NoSuchMethodException e4) {@b@                        return null;@b@                    }@b@                }@b@            }@b@        }@b@    }@b@@b@    public static String getMethodName(Method method, Class<?>[] parameterClasses, String rightCode) {@b@        if (method.getParameterTypes().length > parameterClasses.length) {@b@            Class<?>[] types = method.getParameterTypes();@b@            StringBuilder buf = new StringBuilder(rightCode);@b@            for (int i = parameterClasses.length; i < types.length; i++) {@b@                if (buf.length() > 0) {@b@                    buf.append(",");@b@                }@b@                Class<?> type = types[i];@b@                String def;@b@                if (type == boolean.class) {@b@                    def = "false";@b@                } else if (type == char.class) {@b@                    def = "\'\\0\'";@b@                } else if (type == byte.class@b@                        || type == short.class@b@                        || type == int.class@b@                        || type == long.class@b@                        || type == float.class@b@                        || type == double.class) {@b@                    def = "0";@b@                } else {@b@                    def = "null";@b@                }@b@                buf.append(def);@b@            }@b@        }@b@        return method.getName() + "(" + rightCode + ")";@b@    }@b@@b@    public static Method searchMethod(Class<?> currentClass, String name, Class<?>[] parameterTypes) throws NoSuchMethodException {@b@        if (currentClass == null) {@b@            throw new NoSuchMethodException("class == null");@b@        }@b@        try {@b@            return currentClass.getMethod(name, parameterTypes);@b@        } catch (NoSuchMethodException e) {@b@            for (Method method : currentClass.getMethods()) {@b@                if (method.getName().equals(name)@b@                        && parameterTypes.length == method.getParameterTypes().length@b@                        && Modifier.isPublic(method.getModifiers())) {@b@                    if (parameterTypes.length > 0) {@b@                        Class<?>[] types = method.getParameterTypes();@b@                        boolean match = true;@b@                        for (int i = 0; i < parameterTypes.length; i++) {@b@                            if (!types[i].isAssignableFrom(parameterTypes[i])) {@b@                                match = false;@b@                                break;@b@                            }@b@                        }@b@                        if (!match) {@b@                            continue;@b@                        }@b@                    }@b@                    return method;@b@                }@b@            }@b@            throw e;@b@        }@b@    }@b@@b@    public static String getInitCode(Class<?> type) {@b@        if (byte.class.equals(type)@b@                || short.class.equals(type)@b@                || int.class.equals(type)@b@                || long.class.equals(type)@b@                || float.class.equals(type)@b@                || double.class.equals(type)) {@b@            return "0";@b@        } else if (char.class.equals(type)) {@b@            return "'\\0'";@b@        } else if (boolean.class.equals(type)) {@b@            return "false";@b@        } else {@b@            return "null";@b@        }@b@    }@b@@b@    public static <K, V> Map<K, V> toMap(Map.Entry<K, V>[] entries) {@b@        Map<K, V> map = new HashMap<K, V>();@b@        if (entries != null && entries.length > 0) {@b@            for (Map.Entry<K, V> enrty : entries) {@b@                map.put(enrty.getKey(), enrty.getValue());@b@            }@b@        }@b@        return map;@b@    }@b@@b@}