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package com.sap.it.commons.jmx;

import java.lang.reflect.Method;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

import javax.management.MBeanAttributeInfo;
import javax.management.MBeanOperationInfo;
import javax.management.MBeanParameterInfo;

class MBeanInfoCache {
    private static final Map> PRIMITIVE_CLASSES = new HashMap>(16);

    static {
        Class[] prims = { boolean.class, byte.class, short.class, int.class, long.class, float.class, double.class, char.class };
        for (Class c : prims) {
            PRIMITIVE_CLASSES.put(c.getName(), c);
        }
    }

    private final Class mbeanInterface;

    private final Map attributes = new ConcurrentHashMap();

    private final Map operations = new ConcurrentHashMap();

    public MBeanInfoCache(Class mbeanInterface) {
        this.mbeanInterface = mbeanInterface;
    }

    public Method methodFor(MBeanOperationInfo op) {
        Method result = operations.get(op);
        if (result == null) {
            final MBeanParameterInfo[] params = op.getSignature();
            final String[] paramTypes = new String[params.length];
            for (int i = 0; i < params.length; i++) {
                paramTypes[i] = params[i].getType();
            }
            result = findMethod(op.getName(), paramTypes);
            if (result != null) {
                operations.put(op, result);
            }
        }
        return result;
    }

    public Method methodFor(MBeanAttributeInfo attr) {
        Method result = attributes.get(attr);
        if (result == null) {
            String methodWithAnnotation;
            if (attr.isIs()) {
                methodWithAnnotation = "is" + attr.getName(); //$NON-NLS-1$
            } else {
                methodWithAnnotation = "get" + attr.getName(); //$NON-NLS-1$
            }
            // Open issue: is it possible to have a writeble non-readable
            // attribute?
            result = findMethod(methodWithAnnotation, new String[0]);
            if (result != null) {
                attributes.put(attr, result);
            }
        }
        return result;
    }

    public Class getMbeanInterface() {
        return mbeanInterface;
    }

    private final Method findMethod(String name, String... paramTypes) {

        try {
            final ClassLoader loader = mbeanInterface.getClassLoader();
            final Class[] paramClasses = new Class[paramTypes.length];
            for (int i = 0; i < paramTypes.length; i++) {
                paramClasses[i] = classForName(paramTypes[i], loader);
            }
            return mbeanInterface.getMethod(name, paramClasses);
        } catch (RuntimeException e) {
            // avoid accidentally catching unexpected runtime exceptions
            throw e;
        } catch (Exception e) {
            return null;
        }
    }

    private static Class classForName(String name, ClassLoader loader) throws ClassNotFoundException {

        Class c = PRIMITIVE_CLASSES.get(name);
        if (c == null) {
            c = Class.forName(name, false, loader);
        }
        return c;
    }

}