ASMUtils.java

package com.alibaba.fastjson.util;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Type;

public class ASMUtils {

    public static boolean isAndroid(String vmName) {
        return "Dalvik".equals(vmName)
                || "Lemur".equals(vmName) // aliyun-vm name
                ;
    }

    public static boolean isAndroid() {
        return isAndroid(System.getProperty("java.vm.name"));
    }

    public static String getDesc(Method method) {
        StringBuffer buf = new StringBuffer();
        buf.append("(");
        java.lang.Class<?>[] types = method.getParameterTypes();
        for (int i = 0; i < types.length; ++i) {
            buf.append(getDesc(types[i]));
        }
        buf.append(")");
        buf.append(getDesc(method.getReturnType()));
        return buf.toString();
    }

    public static String getDesc(Constructor<?> constructor) {
        StringBuffer buf = new StringBuffer();
        buf.append("(");
        java.lang.Class<?>[] types = constructor.getParameterTypes();
        for (int i = 0; i < types.length; ++i) {
            buf.append(getDesc(types[i]));
        }
        buf.append(")V");
        return buf.toString();
    }

    public static String getDesc(Class<?> returnType) {
        if (returnType.isPrimitive()) {
            return getPrimitiveLetter(returnType);
        } else if (returnType.isArray()) {
            return "[" + getDesc(returnType.getComponentType());
        } else {
            return "L" + getType(returnType) + ";";
        }
    }

    public static String getType(Class<?> parameterType) {
        if (parameterType.isArray()) {
            return "[" + getDesc(parameterType.getComponentType());
        } else {
            if (!parameterType.isPrimitive()) {
                String clsName = parameterType.getName();
                return clsName.replaceAll("\\.", "/");
            } else {
                return getPrimitiveLetter(parameterType);
            }
        }
    }

    public static String getPrimitiveLetter(Class<?> type) {
        if (Integer.TYPE.equals(type)) {
            return "I";
        } else if (Void.TYPE.equals(type)) {
            return "V";
        } else if (Boolean.TYPE.equals(type)) {
            return "Z";
        } else if (Character.TYPE.equals(type)) {
            return "C";
        } else if (Byte.TYPE.equals(type)) {
            return "B";
        } else if (Short.TYPE.equals(type)) {
            return "S";
        } else if (Float.TYPE.equals(type)) {
            return "F";
        } else if (Long.TYPE.equals(type)) {
            return "J";
        } else if (Double.TYPE.equals(type)) {
            return "D";
        }

        throw new IllegalStateException("Type: " + type.getCanonicalName() + " is not a primitive type");
    }

    public static Type getMethodType(Class<?> clazz, String methodName) {
        try {
            Method method = clazz.getMethod(methodName);

            return method.getGenericReturnType();
        } catch (Exception ex) {
            return null;
        }
    }

    public static Type getFieldType(Class<?> clazz, String fieldName) {
        try {
            Field field = clazz.getField(fieldName);

            return field.getGenericType();
        } catch (Exception ex) {
            return null;
        }
    }
}