java不用jni，也可以获得当前系统性能信息

最近做个项目，就是要取得cpu占有率等等的系统信息，一开始以为要用动态链接库了，但后来发现可以像下面这样做，不去调用jni，这样省去了很多看新技术的时间o(∩_∩)o...

在Java中，可以获得总的物理内存、剩余的物理内存、已使用的物理内存等信息，下面例子可以取得这些信息，并且获得在Windows下的内存使用率。
首先编写一个MonitorInfoBean类，用来装载监控的一些信息，包括物理内存、剩余的物理内存、已使用的物理内存、内存使用率等字段，该类的代码如下：

package com.amgkaka.performance;

/** *//**
* 监视信息的JavaBean类.
* @author  amg
* @version 1.0
* Creation date: 2008-4-25 - 上午10:37:00
*/
public class MonitorInfoBean {
/** *//** 可使用内存. */
private long totalMemory;

/** *//** 剩余内存. */
private long freeMemory;

/** *//** 最大可使用内存. */
private long maxMemory;

/** *//** 操作系统. */
private String osName;

/** *//** 总的物理内存. */
private long totalMemorySize;

/** *//** 剩余的物理内存. */
private long freePhysicalMemorySize;

/** *//** 已使用的物理内存. */
private long usedMemory;

/** *//** 线程总数. */
private int totalThread;

/** *//** cpu使用率. */
private double cpuRatio;

public long getFreeMemory() {
return freeMemory;
}

public void setFreeMemory(long freeMemory) {
this.freeMemory = freeMemory;
}

public long getFreePhysicalMemorySize() {
return freePhysicalMemorySize;
}

public void setFreePhysicalMemorySize(long freePhysicalMemorySize) {
this.freePhysicalMemorySize = freePhysicalMemorySize;
}

public long getMaxMemory() {
return maxMemory;
}

public void setMaxMemory(long maxMemory) {
this.maxMemory = maxMemory;
}

public String getOsName() {
return osName;
}

public void setOsName(String osName) {
this.osName = osName;
}

public long getTotalMemory() {
return totalMemory;
}

public void setTotalMemory(long totalMemory) {
this.totalMemory = totalMemory;
}

public long getTotalMemorySize() {
return totalMemorySize;
}

public void setTotalMemorySize(long totalMemorySize) {
this.totalMemorySize = totalMemorySize;
}

public int getTotalThread() {
return totalThread;
}

public void setTotalThread(int totalThread) {
this.totalThread = totalThread;
}

public long getUsedMemory() {
return usedMemory;
}

public void setUsedMemory(long usedMemory) {
this.usedMemory = usedMemory;
}

public double getCpuRatio() {
return cpuRatio;
}

public void setCpuRatio(double cpuRatio) {
this.cpuRatio = cpuRatio;
}
}

接着编写一个获得当前的监控信息的接口，该类的代码如下所示：

package com.amgkaka.performance;

/** *//**
* 获取系统信息的业务逻辑类接口.
* @author amg * @version 1.0
* Creation date: 2008-3-11 - 上午10:06:06
*/
public interface IMonitorService {
/** *//**
* 获得当前的监控对象.
* @return 返回构造好的监控对象
* @throws Exception
* @author amgkaka
* Creation date: 2008-4-25 - 上午10:45:08
*/
public MonitorInfoBean getMonitorInfoBean() throws Exception;

}

该类的实现类MonitorServiceImpl如下所示：

package com.amgkaka.performance;

import java.io.InputStreamReader;
import java.io.LineNumberReader;

import sun.management.ManagementFactory;

import com.sun.management.OperatingSystemMXBean;

/** *//**
* 获取系统信息的业务逻辑实现类.
* @author amg * @version 1.0 Creation date: 2008-3-11 - 上午10:06:06
*/
public class MonitorServiceImpl implements IMonitorService {
//可以设置长些，防止读到运行此次系统检查时的cpu占用率，就不准了
private static final int CPUTIME = 5000;

private static final int PERCENT = 100;

private static final int FAULTLENGTH = 10;

/** *//**
* 获得当前的监控对象.
* @return 返回构造好的监控对象
* @throws Exception
* @author amg     * Creation date: 2008-4-25 - 上午10:45:08
*/
public MonitorInfoBean getMonitorInfoBean() throws Exception {
int kb = 1024;

// 可使用内存
long totalMemory = Runtime.getRuntime().totalMemory() / kb;
// 剩余内存
long freeMemory = Runtime.getRuntime().freeMemory() / kb;
// 最大可使用内存
long maxMemory = Runtime.getRuntime().maxMemory() / kb;

OperatingSystemMXBean osmxb = (OperatingSystemMXBean) ManagementFactory
.getOperatingSystemMXBean();

// 操作系统
String osName = System.getProperty("os.name");
// 总的物理内存
long totalMemorySize = osmxb.getTotalPhysicalMemorySize() / kb;
// 剩余的物理内存
long freePhysicalMemorySize = osmxb.getFreePhysicalMemorySize() / kb;
// 已使用的物理内存
long usedMemory = (osmxb.getTotalPhysicalMemorySize() - osmxb
.getFreePhysicalMemorySize())
/ kb;

// 获得线程总数
ThreadGroup parentThread;
for (parentThread = Thread.currentThread().getThreadGroup(); parentThread
.getParent() != null; parentThread = parentThread.getParent())
;
int totalThread = parentThread.activeCount();

double cpuRatio = 0;
if (osName.toLowerCase().startsWith("windows")) {
cpuRatio = this.getCpuRatioForWindows();
}

// 构造返回对象
MonitorInfoBean infoBean = new MonitorInfoBean();
infoBean.setFreeMemory(freeMemory);
infoBean.setFreePhysicalMemorySize(freePhysicalMemorySize);
infoBean.setMaxMemory(maxMemory);
infoBean.setOsName(osName);
infoBean.setTotalMemory(totalMemory);
infoBean.setTotalMemorySize(totalMemorySize);
infoBean.setTotalThread(totalThread);
infoBean.setUsedMemory(usedMemory);
infoBean.setCpuRatio(cpuRatio);
return infoBean;
}

/** *//**
* 获得CPU使用率.
* @return 返回cpu使用率
* @author amg     * Creation date: 2008-4-25 - 下午06:05:11
*/
private double getCpuRatioForWindows() {
try {
String procCmd = System.getenv("windir")
+ "\\system32\\wbem\\wmic.exe process get Caption,CommandLine,"
+ "KernelModeTime,ReadOperationCount,ThreadCount,UserModeTime,WriteOperationCount";
// 取进程信息
long[] c0 = readCpu(Runtime.getRuntime().exec(procCmd));
Thread.sleep(CPUTIME);
long[] c1 = readCpu(Runtime.getRuntime().exec(procCmd));
if (c0 != null && c1 != null) {
long idletime = c1[0] - c0[0];
long busytime = c1[1] - c0[1];
return Double.valueOf(
PERCENT * (busytime) / (busytime + idletime))
.doubleValue();
} else {
return 0.0;
}
} catch (Exception ex) {
ex.printStackTrace();
return 0.0;
}
}

/** *//**
* 读取CPU信息.
* @param proc
* @return
* @author amg     * Creation date: 2008-4-25 - 下午06:10:14
*/
private long[] readCpu(final Process proc) {
long[] retn = new long[2];
try {
proc.getOutputStream().close();
InputStreamReader ir = new InputStreamReader(proc.getInputStream());
LineNumberReader input = new LineNumberReader(ir);
String line = input.readLine();
if (line == null || line.length() < FAULTLENGTH) {
return null;
}
int capidx = line.indexOf("Caption");
int cmdidx = line.indexOf("CommandLine");
int rocidx = line.indexOf("ReadOperationCount");
int umtidx = line.indexOf("UserModeTime");
int kmtidx = line.indexOf("KernelModeTime");
int wocidx = line.indexOf("WriteOperationCount");
long idletime = 0;
long kneltime = 0;
long usertime = 0;
while ((line = input.readLine()) != null) {
if (line.length() < wocidx) {
continue;
}
// 字段出现顺序：Caption,CommandLine,KernelModeTime,ReadOperationCount,
// ThreadCount,UserModeTime,WriteOperation
String caption = Bytes.substring(line, capidx, cmdidx - 1)
.trim();
String cmd = Bytes.substring(line, cmdidx, kmtidx - 1).trim();
if (cmd.indexOf("wmic.exe") >= 0) {
continue;
}
// log.info("line="+line);
if (caption.equals("System Idle Process")
|| caption.equals("System")) {
idletime += Long.valueOf(
Bytes.substring(line, kmtidx, rocidx - 1).trim())
.longValue();
idletime += Long.valueOf(
Bytes.substring(line, umtidx, wocidx - 1).trim())
.longValue();
continue;
}

kneltime += Long.valueOf(
Bytes.substring(line, kmtidx, rocidx - 1).trim())
.longValue();
usertime += Long.valueOf(
Bytes.substring(line, umtidx, wocidx - 1).trim())
.longValue();
}
retn[0] = idletime;
retn[1] = kneltime + usertime;
return retn;
} catch (Exception ex) {
ex.printStackTrace();
} finally {
try {
proc.getInputStream().close();
} catch (Exception e) {
e.printStackTrace();
}
}
return null;
}

/** *//**
* 测试方法.
* @param args
* @throws Exception
* @author amg     * Creation date: 2008-4-30 - 下午04:47:29
*/
public static void main(String[] args) throws Exception {
IMonitorService service = new MonitorServiceImpl();
MonitorInfoBean monitorInfo = service.getMonitorInfoBean();
System.out.println("cpu占有率=" + monitorInfo.getCpuRatio());

System.out.println("可使用内存=" + monitorInfo.getTotalMemory());
System.out.println("剩余内存=" + monitorInfo.getFreeMemory());
System.out.println("最大可使用内存=" + monitorInfo.getMaxMemory());

System.out.println("操作系统=" + monitorInfo.getOsName());
System.out.println("总的物理内存=" + monitorInfo.getTotalMemorySize() + "kb");
System.out.println("剩余的物理内存=" + monitorInfo.getFreeMemory() + "kb");
System.out.println("已使用的物理内存=" + monitorInfo.getUsedMemory() + "kb");
System.out.println("线程总数=" + monitorInfo.getTotalThread() + "kb");
}
}

该实现类中需要用到一个自己编写byte的工具类，该类的代码如下所示：

package com.amgkaka.performance;

/** *//**
* byte操作类.
* @author amg * @version 1.0
* Creation date: 2008-4-30 - 下午04:57:23
*/
public class Bytes {
/** *//**
* 由于String.subString对汉字处理存在问题（把一个汉字视为一个字节)，因此在
* 包含汉字的字符串时存在隐患，现调整如下：
* @param src 要截取的字符串
* @param start_idx 开始坐标（包括该坐标)
* @param end_idx   截止坐标（包括该坐标）
* @return
*/
public static String substring(String src, int start_idx, int end_idx){
byte[] b = src.getBytes();
String tgt = "";
for(int i=start_idx; i<=end_idx; i++){
tgt +=(char)b[i];
}
return tgt;
}
}

运行下MonitorBeanImpl类，读者将会看到当前的内存、cpu利用率等信息。

（转自：http://kakaluyi.iteye.com/blog/211492）