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| 25 | |||
| 26 | <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> | ||
| 27 | <html> | ||
| 28 | <body bgcolor="white"> | ||
| 29 | |||
| 30 | Provides the management interfaces for monitoring and management of the | ||
| 31 | Java virtual machine and other components in the Java runtime. | ||
| 32 | It allows both local and remote | ||
| 33 | monitoring and management of the running Java virtual machine. | ||
| 34 | <p> | ||
| 35 | |||
| 36 | <h4><a name="MXBean">Platform MXBean</a></h4> | ||
| 37 | <p> | ||
| 38 | A platform MXBean is a <i>managed bean</i> that | ||
| 39 | conforms to the <a href="../../../javax/management/package-summary.html">JMX</a> | ||
| 40 | Instrumentation Specification and only uses a set of basic data types. | ||
| 41 | Each platform MXBean is a {@link java.lang.management.PlatformManagedObject} | ||
| 42 | with a unique | ||
| 43 | {@linkplain java.lang.management.PlatformManagedObject#getObjectName name}. | ||
| 44 | <p> | ||
| 45 | <h4>ManagementFactory</h4> | ||
| 46 | |||
| 47 | <p>The {@link java.lang.management.ManagementFactory} class is the management | ||
| 48 | factory class for the Java platform. This class provides a set of | ||
| 49 | static factory methods to obtain the MXBeans for the Java platform | ||
| 50 | to allow an application to access the MXBeans directly. | ||
| 51 | |||
| 52 | <p>A <em>platform MBeanServer</em> can be accessed with the | ||
| 53 | {@link java.lang.management.ManagementFactory#getPlatformMBeanServer | ||
| 54 | getPlatformMBeanServer} method. On the first call to this method, | ||
| 55 | it creates the platform MBeanServer and registers all platform MXBeans | ||
| 56 | including {@linkplain java.lang.management.PlatformManagedObject | ||
| 57 | platform MXBeans}. | ||
| 58 | Each platform MXBean is registered with a unique name defined in | ||
| 59 | the specification of the management interface. | ||
| 60 | This is a single MBeanServer that can be shared by different managed | ||
| 61 | components running within the same Java virtual machine. | ||
| 62 | |||
| 63 | <h4>Interoperability</h4> | ||
| 64 | |||
| 65 | <p>A management application and a platform MBeanServer of a running | ||
| 66 | virtual machine can interoperate | ||
| 67 | without requiring classes used by the platform MXBean interfaces. | ||
| 68 | The data types being transmitted between the JMX connector | ||
| 69 | server and the connector client are JMX | ||
| 70 | {@linkplain javax.management.openmbean.OpenType open types} and | ||
| 71 | this allows interoperation across versions. | ||
| 72 | A data type used by the MXBean interfaces are mapped to an | ||
| 73 | open type when being accessed via MBeanServer interface. | ||
| 74 | See the <a href="../../../javax/management/MXBean.html#MXBean-spec"> | ||
| 75 | MXBean</a> specification for details. | ||
| 76 | |||
| 77 | <h4><a name="examples">Ways to Access MXBeans</a></h4> | ||
| 78 | |||
| 79 | <p>An application can monitor the instrumentation of the | ||
| 80 | Java virtual machine and the runtime in the following ways: | ||
| 81 | <p> | ||
| 82 | <b>1. Direct access to an MXBean interface</b> | ||
| 83 | <p> | ||
| 84 | <ul> | ||
| 85 | <li>Get an MXBean instance locally in the running Java virtual machine:<p> | ||
| 86 | <pre> | ||
| 87 | RuntimeMXBean mxbean = ManagementFactory.getRuntimeMXBean(); | ||
| 88 | |||
| 89 | // Get the standard attribute "VmVendor" | ||
| 90 | String vendor = mxbean.getVmVendor(); | ||
| 91 | </pre> | ||
| 92 | <p>Or by calling the | ||
| 93 | {@link java.lang.management.ManagementFactory#getPlatformMXBean(Class) | ||
| 94 | getPlatformMXBean} or | ||
| 95 | {@link java.lang.management.ManagementFactory#getPlatformMXBeans(Class) | ||
| 96 | getPlatformMXBeans} method: | ||
| 97 | <pre> | ||
| 98 | RuntimeMXBean mxbean = ManagementFactory.getPlatformMXBean(RuntimeMXBean.class); | ||
| 99 | |||
| 100 | // Get the standard attribute "VmVendor" | ||
| 101 | String vendor = mxbean.getVmVendor(); | ||
| 102 | </pre> | ||
| 103 | <p> | ||
| 104 | </li> | ||
| 105 | <li>Construct an MXBean proxy instance that forwards the | ||
| 106 | method calls to a given MBeanServer:<p> | ||
| 107 | <pre> | ||
| 108 | MBeanServerConnection mbs; | ||
| 109 | |||
| 110 | // Connect to a running JVM (or itself) and get MBeanServerConnection | ||
| 111 | // that has the JVM MBeans registered in it | ||
| 112 | ... | ||
| 113 | |||
| 114 | // Get a MBean proxy for RuntimeMXBean interface | ||
| 115 | RuntimeMXBean proxy = | ||
| 116 | {@link java.lang.management.ManagementFactory#getPlatformMXBean(MBeanServerConnection, Class) | ||
| 117 | ManagementFactory.getPlatformMXBean}(mbs, | ||
| 118 | RuntimeMXBean.class); | ||
| 119 | // Get standard attribute "VmVendor" | ||
| 120 | String vendor = proxy.getVmVendor(); | ||
| 121 | </pre> | ||
| 122 | <p>A proxy is typically used to access an MXBean | ||
| 123 | in a remote Java virtual machine. | ||
| 124 | An alternative way to create an MXBean proxy is: | ||
| 125 | <pre> | ||
| 126 | RuntimeMXBean proxy = | ||
| 127 | {@link java.lang.management.ManagementFactory#newPlatformMXBeanProxy | ||
| 128 | ManagementFactory.newPlatformMXBeanProxy}(mbs, | ||
| 129 | ManagementFactory.RUNTIME_MXBEAN_NAME, | ||
| 130 | RuntimeMXBean.class); | ||
| 131 | </pre> | ||
| 132 | </li> | ||
| 133 | </ul> | ||
| 134 | <p> | ||
| 135 | <b>2. Indirect access to an MXBean interface via MBeanServer</b><p> | ||
| 136 | <ul> | ||
| 137 | <li>Go through the | ||
| 138 | {@link java.lang.management.ManagementFactory#getPlatformMBeanServer | ||
| 139 | platform MBeanServer} to access MXBeans locally or | ||
| 140 | a specific {@code MBeanServerConnection} to access | ||
| 141 | MXBeans remotely. | ||
| 142 | The attributes and operations of an MXBean use only | ||
| 143 | <em>JMX open types</em> which include basic data types, | ||
| 144 | {@link javax.management.openmbean.CompositeData CompositeData}, | ||
| 145 | and {@link javax.management.openmbean.TabularData TabularData} | ||
| 146 | defined in {@link javax.management.openmbean.OpenType OpenType}.<p> | ||
| 147 | <pre> | ||
| 148 | MBeanServerConnection mbs; | ||
| 149 | |||
| 150 | // Connect to a running JVM (or itself) and get MBeanServerConnection | ||
| 151 | // that has the JVM MXBeans registered in it | ||
| 152 | ... | ||
| 153 | |||
| 154 | try { | ||
| 155 | // Assuming the RuntimeMXBean has been registered in mbs | ||
| 156 | ObjectName oname = new ObjectName(ManagementFactory.RUNTIME_MXBEAN_NAME); | ||
| 157 | |||
| 158 | // Get standard attribute "VmVendor" | ||
| 159 | String vendor = (String) mbs.getAttribute(oname, "VmVendor"); | ||
| 160 | } catch (....) { | ||
| 161 | // Catch the exceptions thrown by ObjectName constructor | ||
| 162 | // and MBeanServer.getAttribute method | ||
| 163 | ... | ||
| 164 | } | ||
| 165 | </pre> | ||
| 166 | </li> | ||
| 167 | </ul> | ||
| 168 | |||
| 169 | |||
| 170 | <h4><a name="extension">Platform Extension</a></h4> | ||
| 171 | |||
| 172 | <p>A Java virtual machine implementation may add its platform extension to | ||
| 173 | the management interface by defining platform-dependent | ||
| 174 | interfaces that extend the standard management interfaces to include | ||
| 175 | platform-specific metrics and management operations. | ||
| 176 | The static factory methods in the <tt>ManagementFactory</tt> class will | ||
| 177 | return the MXBeans with the platform extension. | ||
| 178 | |||
| 179 | <p> | ||
| 180 | It is recommended to name the platform-specific attributes with | ||
| 181 | a vendor-specific prefix such as the vendor's name to | ||
| 182 | avoid collisions of the attribute name between the future extension | ||
| 183 | to the standard management interface and the platform extension. | ||
| 184 | If the future extension to the standard management interface defines | ||
| 185 | a new attribute for a management interface and the attribute name | ||
| 186 | is happened to be same as some vendor-specific attribute's name, | ||
| 187 | the applications accessing that vendor-specific attribute would have | ||
| 188 | to be modified to cope with versioning and compatibility issues. | ||
| 189 | |||
| 190 | <p>Below is an example showing how to access an attribute | ||
| 191 | from the platform extension: | ||
| 192 | |||
| 193 | <p> | ||
| 194 | 1) Direct access to the Oracle-specific MXBean interface | ||
| 195 | <blockquote> | ||
| 196 | <pre> | ||
| 197 | List<com.sun.management.GarbageCollectorMXBean> mxbeans = | ||
| 198 | ManagementFactory.getPlatformMXBeans(com.sun.management.GarbageCollectorMXBean.class); | ||
| 199 | |||
| 200 | for (com.sun.management.GarbageCollectorMXBean gc : mxbeans) { | ||
| 201 | // Get the standard attribute "CollectionCount" | ||
| 202 | String count = mxbean.getCollectionCount(); | ||
| 203 | |||
| 204 | // Get the platform-specific attribute "LastGcInfo" | ||
| 205 | GcInfo gcinfo = gc.getLastGcInfo(); | ||
| 206 | ... | ||
| 207 | } | ||
| 208 | </pre> | ||
| 209 | </blockquote> | ||
| 210 | |||
| 211 | <p> | ||
| 212 | 2) Access the Oracle-specific MXBean interface via <tt>MBeanServer</tt> | ||
| 213 | through proxy | ||
| 214 | |||
| 215 | <blockquote><pre> | ||
| 216 | MBeanServerConnection mbs; | ||
| 217 | |||
| 218 | // Connect to a running JVM (or itself) and get MBeanServerConnection | ||
| 219 | // that has the JVM MXBeans registered in it | ||
| 220 | ... | ||
| 221 | |||
| 222 | List<com.sun.management.GarbageCollectorMXBean> mxbeans = | ||
| 223 | ManagementFactory.getPlatformMXBeans(mbs, com.sun.management.GarbageCollectorMXBean.class); | ||
| 224 | |||
| 225 | for (com.sun.management.GarbageCollectorMXBean gc : mxbeans) { | ||
| 226 | // Get the standard attribute "CollectionCount" | ||
| 227 | String count = mxbean.getCollectionCount(); | ||
| 228 | |||
| 229 | // Get the platform-specific attribute "LastGcInfo" | ||
| 230 | GcInfo gcinfo = gc.getLastGcInfo(); | ||
| 231 | ... | ||
| 232 | } | ||
| 233 | </pre></blockquote> | ||
| 234 | |||
| 235 | <p> Unless otherwise noted, passing a <tt>null</tt> argument to a constructor | ||
| 236 | or method in any class or interface in this package will cause a {@link | ||
| 237 | java.lang.NullPointerException NullPointerException} to be thrown. | ||
| 238 | |||
| 239 | <p> The java.lang.management API is thread-safe. | ||
| 240 | |||
| 241 | @see <a href="../../../javax/management/package-summary.html"> | ||
| 242 | JMX Specification.</a> | ||
| 243 | |||
| 244 | @author Mandy Chung | ||
| 245 | @since 1.5 | ||
| 246 | |||
| 247 | </body> | ||
| 248 | </html> | ||