难道只能用JNI实现JMX或者JDMK的instrumentation layer？

最近在用JDMK做网上硬件资源和软件资源的监控，目的是得到这些资源的状态信息（例如：CPU利用率，内存利率，操作系统名称等），按照sun官方提供的JDMK的一个例子，是这样的：

利用JDMK所提供的mibgen工具，将一个MIB definition文件转换成多个MIB MBean，其中包含：一个主要的MBean类，它能够代表所有的MIB；代表SNMP groups或者entities的多个MBean和与之对应的metadata类；代表SNMP tables的多个类；代表SNMP enumerated type的多个类。

在产生的类中，该例子提供了一些实现，现在举个实现的SNMP的MIB system group分支上的MBean的例子：

SystemMBean类 部分代码

// Generated by mibgen version 5.1 (05/20/05) when compiling RFC1213-MIB in standard metadata mode.
import com.sun.management.snmp.SnmpStatusException;

/**
 * This interface is used for representing the remote management interface for the "System" MBean.
 */
public interface SystemMBean {

    /**
     * Getter for the "SysLocation" variable.
     */
    public String getSysLocation() throws SnmpStatusException;

    /**
     * Setter for the "SysLocation" variable.
     */
    public void setSysLocation(String x) throws SnmpStatusException;

    /**
     * Checker for the "SysLocation" variable.
     */
    public void checkSysLocation(String x) throws SnmpStatusException;

    /**
     * Getter for the "SysName" variable.
     */
    public String getSysName() throws SnmpStatusException;

    /**
     * Setter for the "SysName" variable.
     */
    public void setSysName(String x) throws SnmpStatusException;

    /**
     * Checker for the "SysName" variable.
     */
    public void checkSysName(String x) throws SnmpStatusException;

   ………………
}

System类 部分代码

// Generated by mibgen version 5.1 (05/20/05) when compiling RFC1213-MIB.
import java.io.Serializable;

/**
 * The class is used for implementing the "System" group.
 * The group is defined with the following oid: 1.3.6.1.2.1.1.
 */
public class System implements SystemMBean, Serializable {

    /**
     * Variable for storing the value of "SysLocation".
     * The variable is identified by: "1.3.6.1.2.1.1.6".
     */
    protected String SysLocation = new String("JDMK 5.1");

    /**
     * Variable for storing the value of "SysName".
     * The variable is identified by: "1.3.6.1.2.1.1.5".
     */
    protected String SysName = new String("JDMK 5.1");

    /**
     * Variable for storing the value of "SysContact".
     * The variable is identified by: "1.3.6.1.2.1.1.4".
     */
    protected String SysContact = new String("JDMK 5.1");

    /**
     * Variable for storing the value of "SysUpTime".
     * The variable is identified by: "1.3.6.1.2.1.1.3".
     */
    protected Long SysUpTime = new Long(1);

    /**
     * Variable for storing the value of "SysObjectID".
     * The variable is identified by: "1.3.6.1.2.1.1.2".
     */
    protected String SysObjectID = new String("1.3.6.1.4.1.42");

    /**
     * Variable for storing the value of "SysDescr".
     * The variable is identified by: "1.3.6.1.2.1.1.1".
     */
    protected String SysDescr = new String("JDMK 5.1");

    /**
     * Variable for storing the value of "SysServices".
     * The variable is identified by: "1.3.6.1.2.1.1.7".
     */
    protected Integer SysServices = new Integer(1);


    /**
     * Constructor for the "System" group.
     * If the group contains a table, the entries created through an SNMP SET will not be registered in Java DMK.
     */
    public System(SnmpMib myMib) {
    }


    /**
     * Constructor for the "System" group.
     * If the group contains a table, the entries created through an SNMP SET will be AUTOMATICALLY REGISTERED in Java DMK.
     */
    public System(SnmpMib myMib, MBeanServer server) {
    }

    /**
     * Getter for the "SysLocation" variable.
     */
    public String getSysLocation() throws SnmpStatusException {
        return SysLocation;
    }

    /**
     * Setter for the "SysLocation" variable.
     */
    public void setSysLocation(String x) throws SnmpStatusException {
        SysLocation = x;
    }

    /**
     * Checker for the "SysLocation" variable.
     */
    public void checkSysLocation(String x) throws SnmpStatusException {
        //
        // Add your own checking policy.
        //
    }

    /**
     * Getter for the "SysName" variable.
     */
    public String getSysName() throws SnmpStatusException {
        return SysName;
    }

    /**
     * Setter for the "SysName" variable.
     */
    public void setSysName(String x) throws SnmpStatusException {
        SysName = x;
    }

    /**
     * Checker for the "SysName" variable.
     */
    public void checkSysName(String x) throws SnmpStatusException {
        //
        // Add your own checking policy.
        //
    }
………………
}

在该例子中，给出了继承System的类SystemImpl

SystemImpl 代码

 * @(#)file      SystemImpl.java
import java.net.InetAddress;


/**
 * The SystemImpl class provides an simple implementation of the "System" group.
 */

public class SystemImpl extends System {

    // MBean properties.
    //

    // Start up time of the agent.
    //
    private long startUpTime = 0;

    /**
     * Constructors.
     */
    public SystemImpl(SnmpMib myMib) {

        super(myMib);
        init();
    }

    public SystemImpl(SnmpMib myMib, MBeanServer server) {

        super(myMib, server);
      //  java.lang.System.out.println(((SnmpAdaptorServer)myMib.getSnmpAdaptor()).getSnmpInGetNexts()+"adffds");

        init();
    }

    private void init() {

        // Initialize the system description using some system properties.
        //
        try {
            SysDescr = java.lang.System.getProperty("os.name") + " " +
                java.lang.System.getProperty("os.arch") + " " +
                java.lang.System.getProperty("os.version");
        } catch(SecurityException e) {
            // Do not process the exception
        }

        // Initialize the system name using the hostname.
        //
        try {
            SysName = (InetAddress.getLocalHost()).getHostName();
        } catch(UnknownHostException e) {
            // Do not process the exception
        }

        // Initialize the system contact using some system properties.
        //
        try {
            SysContact = java.lang.System.getProperty("user.name");
        } catch(SecurityException e) {
            // Do not process the exception
        }

        // Initialize the set of services. Assume the agent only deals
        // with application layer.
        //
        SysServices = new Integer(72);

        // Initialize the location with a dummy string.
        //
        SysLocation = "Sample implementation of system group.";

        // For the sysUpTime, use the time the agent started...
        //
        startUpTime = java.lang.System.currentTimeMillis();
    }

    public Long getSysUpTime() throws SnmpStatusException {

        long diff = java.lang.System.currentTimeMillis() - startUpTime;
        return new Long(diff);
    }
}

在SystemImpl中，是具体的实现instrumentation layer层中的MBean的例子，但是如果不是获得System group上的信息，而是获得CPU利用率，一般情况下，通过在客户端装snmp agent(net-snmp)，然后用snmpget命令根据OID可以获得CPU利用率。但是在JDMK中，用java实现的话，是不是只能够通过JNI的方式来建立MBean，能否在JDMK下，利用SNMP的OID获得资源的状态信息呢？有没有其他可行的方法呢？