com.ecyrd.management.SimpleMBean.java Source code

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to you under the Apache License, Version 2.0 (the
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   http://www.apache.org/licenses/LICENSE-2.0
    
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 */
package com.ecyrd.management;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Iterator;

import javax.management.*;

import org.apache.commons.lang.StringUtils;

/**
 *  A simple MBean which does not require an interface class unlike
 *  the StandardMBean class.  The methods are exposed through a method
 *  call, which in turn then calls the methods using the Reflection API.
 *  <p>
 *  This class is similar to the javax.management.StandardMBean, but it does
 *  require the API interface to be declared, so it's simpler.  It's not as
 *  powerful, but it does not require you to declare two classes (and keep
 *  them in sync).
 *
 *  @since  2.6
 */
// FIXME: This class should really use Annotations instead of a method call.
// FIXME: Exception handling is not probably according to spec...
public abstract class SimpleMBean implements DynamicMBean {
    protected MBeanInfo m_beanInfo;

    private static Method findGetterSetter(Class<?> clazz, String name, Class<?> parm) {
        try {
            Class<?>[] params = { parm };
            Class<?>[] emptyparms = {};

            Method m = clazz.getDeclaredMethod(name, parm != null ? params : emptyparms);

            return m;
        } catch (Exception e) {
            // There's nothing to do, really - we just return a null.
        }

        return null;
    }

    /**
     *  Create a new SimpleMBean
     *  
     *  @throws NotCompliantMBeanException {@inheritDoc}
     */
    protected SimpleMBean() throws NotCompliantMBeanException {
        //
        //  Create attributes
        //
        String[] attlist = getAttributeNames();
        MBeanAttributeInfo[] attributes = null;

        if (attlist != null) {
            attributes = new MBeanAttributeInfo[attlist.length];

            for (int i = 0; i < attlist.length; i++) {
                String name = attlist[i];
                name = StringUtils.capitalize(name);
                Method getter = findGetterSetter(getClass(), "get" + name, null);

                if (getter == null)
                    getter = findGetterSetter(getClass(), "is" + name, null);

                Method setter = null;

                if (getter != null) {
                    setter = findGetterSetter(getClass(), "set" + name, getter.getReturnType());
                }

                //
                //  Check, if there's a description available
                //
                Method descriptor = findGetterSetter(getClass(), "get" + name + "Description", null);
                String description = "";

                if (descriptor != null) {
                    try {
                        description = (String) descriptor.invoke(this, (Object[]) null);
                    } catch (Exception e) {
                        description = "Exception: " + e.getMessage();
                    }
                }

                MBeanAttributeInfo info;
                try {
                    info = new MBeanAttributeInfo(attlist[i], description, getter, setter);
                } catch (IntrospectionException e) {
                    throw new NotCompliantMBeanException(e.getMessage());
                }

                attributes[i] = info;
            }
        }

        //
        //  Create operations.
        //
        String[] oplist = getMethodNames();
        MBeanOperationInfo[] operations = new MBeanOperationInfo[oplist.length];

        Method[] methods = getClass().getMethods();

        for (int i = 0; i < oplist.length; i++) {
            Method method = null;

            for (int m = 0; m < methods.length; m++) {
                if (methods[m].getName().equals(oplist[i])) {
                    method = methods[m];
                }
            }

            if (method == null) {
                throw new NotCompliantMBeanException(
                        "Class declares method " + oplist[i] + ", yet does not implement it!");
            }

            MBeanOperationInfo info = new MBeanOperationInfo(method.getName(), method);

            operations[i] = info;
        }

        //
        //  Create the actual BeanInfo instance.
        //
        MBeanConstructorInfo[] constructors = null;
        MBeanNotificationInfo[] notifications = null;

        m_beanInfo = new MBeanInfo(getClass().getName(), getDescription(), attributes, constructors, operations,
                notifications);
    }

    /**
     *  Customization hook: Override this to get a description for your MBean.  By default,
     *  this is an empty string.
     *
     *  @return A description for the MBean.
     */
    protected String getDescription() {
        return "";
    }

    /**
     *  Gets an attribute using reflection from the MBean.
     *  
     *  @param name Name of the attribute to find.
     *  @return The value returned by the corresponding getXXX() call
     *  @throws AttributeNotFoundException If there is not such attribute
     *  @throws MBeanException 
     *  @throws ReflectionException
     */
    public Object getAttribute(String name) throws AttributeNotFoundException, MBeanException, ReflectionException {
        Method m;
        Object res = null;
        try {
            String mname = "get" + StringUtils.capitalize(name);
            m = findGetterSetter(getClass(), mname, null);

            if (m == null)
                throw new AttributeNotFoundException(name);
            res = m.invoke(this, (Object[]) null);
        } catch (SecurityException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalArgumentException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IllegalAccessException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

        return res;
    }

    /**
     *  Gets multiple attributes at the same time.
     *  
     *  @param arg0 The attribute names to get
     *  @return A list of attributes 
     */
    public AttributeList getAttributes(String[] arg0) {
        AttributeList list = new AttributeList();

        for (int i = 0; i < arg0.length; i++) {
            try {
                list.add(new Attribute(arg0[i], getAttribute(arg0[i])));
            } catch (AttributeNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (MBeanException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (ReflectionException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        return list;
    }

    /**
     *  Return the MBeanInfo structure.
     *  
     *  @return the MBeanInfo
     */
    public MBeanInfo getMBeanInfo() {
        return m_beanInfo;
    }

    /**
     *  Invokes a particular method.
     *  
     *  @param arg0 Method name
     *  @param arg1 A list of arguments for the invocation
     */
    public Object invoke(String arg0, Object[] arg1, String[] arg2) throws MBeanException, ReflectionException {
        Method[] methods = getClass().getMethods();

        for (int i = 0; i < methods.length; i++) {
            if (methods[i].getName().equals(arg0)) {
                try {
                    return methods[i].invoke(this, arg1);
                } catch (IllegalArgumentException e) {
                    throw new ReflectionException(e, "Wrong arguments");
                } catch (IllegalAccessException e) {
                    throw new ReflectionException(e, "No access");
                } catch (InvocationTargetException e) {
                    throw new ReflectionException(e, "Wrong target");
                }
            }
        }

        throw new ReflectionException(null, "There is no such method " + arg0); // TODO: Can you put a null exception?
    }

    public void setAttribute(Attribute attr)
            throws AttributeNotFoundException, InvalidAttributeValueException, MBeanException, ReflectionException {
        Method m;

        String mname = "set" + StringUtils.capitalize(attr.getName());
        m = findGetterSetter(getClass(), mname, attr.getValue().getClass());

        if (m == null)
            throw new AttributeNotFoundException(attr.getName());

        Object[] args = { attr.getValue() };

        try {
            m.invoke(this, args);
        } catch (IllegalArgumentException e) {
            throw new InvalidAttributeValueException("Faulty argument: " + e.getMessage());
        } catch (IllegalAccessException e) {
            throw new ReflectionException(e, "Cannot access attribute " + e.getMessage());
        } catch (InvocationTargetException e) {
            throw new ReflectionException(e, "Cannot invoke attribute " + e.getMessage());
        }
    }

    public AttributeList setAttributes(AttributeList arg0) {
        AttributeList result = new AttributeList();
        for (Iterator i = arg0.iterator(); i.hasNext();) {
            Attribute attr = (Attribute) i.next();

            //
            //  Attempt to set the attribute.  If it succeeds (no exception),
            //  then we just add it to the list of successfull sets.
            //
            try {
                setAttribute(attr);
                result.add(attr);
            } catch (AttributeNotFoundException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (InvalidAttributeValueException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (MBeanException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            } catch (ReflectionException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }

        return result;
    }

    /**
     *  This method must return a list of attributes which are
     *  exposed by the SimpleMBean.  If there's a getXXX() method
     *  available, it'll be exposed as a getter, and if there's a
     *  setXXX() method available, it'll be exposed as a setter.
     *  For example:
     *  <pre>
     *     public void setFoo( String foo ) ...
     *     public String getFoo() ...
     *
     *     public String[] getAttributeNames()
     *     {
     *         String[] attrs = { "foo" };
     *
     *         return attrs;
     *     }
     *  </pre>
     *  Also, methods starting with "is" are also recognized as getters
     *  (e.g. <code>public boolean isFoo()</code>.)
     *
     *  @return An array of attribute names that can be get and optionally set.
     */
    public abstract String[] getAttributeNames();

    /**
     *  This method must return a list of operations which
     *  are to be exposed by the SimpleMBean.  Note that using overloaded
     *  method names is not supported - only one will be exposed as a JMX method
     *  at random.
     *
     *  @return An array of method names that should be exposed as
     *          JMX operations.
     */
    public abstract String[] getMethodNames();
}