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11 This code is distributed in the hope that it will be useful, but WITHOUT |
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14 version 2 for more details (a copy is included in the LICENSE file that |
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24 --> |
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25 |
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26 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"> |
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27 <html> |
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28 <body bgcolor="white"> |
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29 |
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30 Provides the management interfaces for monitoring and management of the |
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31 Java virtual machine and other components in the Java runtime. |
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32 It allows both local and remote |
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33 monitoring and management of the running Java virtual machine. |
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34 |
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35 <h3><a id="MXBean">Platform MXBean</a></h3> |
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36 <p> |
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37 A platform MXBean is a <i>managed bean</i> that |
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38 conforms to the {@linkplain javax.management JMX} |
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39 Instrumentation Specification and only uses a set of basic data types. |
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40 Each platform MXBean is a {@link java.lang.management.PlatformManagedObject} |
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41 with a unique |
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42 {@linkplain java.lang.management.PlatformManagedObject#getObjectName name}. |
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43 <h3>ManagementFactory</h3> |
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44 |
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45 <p>The {@link java.lang.management.ManagementFactory} class is the management |
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46 factory class for the Java platform. This class provides a set of |
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47 static factory methods to obtain the MXBeans for the Java platform |
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48 to allow an application to access the MXBeans directly. |
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49 |
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50 <p>A <em>platform MBeanServer</em> can be accessed with the |
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51 {@link java.lang.management.ManagementFactory#getPlatformMBeanServer |
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52 getPlatformMBeanServer} method. On the first call to this method, |
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53 it creates the platform MBeanServer and registers all platform MXBeans |
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54 including {@linkplain java.lang.management.PlatformManagedObject |
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55 platform MXBeans}. |
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56 Each platform MXBean is registered with a unique name defined in |
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57 the specification of the management interface. |
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58 This is a single MBeanServer that can be shared by different managed |
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59 components running within the same Java virtual machine. |
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60 |
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61 <h3>Interoperability</h3> |
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62 |
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63 <p>A management application and a platform MBeanServer of a running |
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64 virtual machine can interoperate |
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65 without requiring classes used by the platform MXBean interfaces. |
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66 The data types being transmitted between the JMX connector |
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67 server and the connector client are JMX |
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68 {@linkplain javax.management.openmbean.OpenType open types} and |
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69 this allows interoperation across versions. |
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70 A data type used by the MXBean interfaces are mapped to an |
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71 open type when being accessed via MBeanServer interface. |
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72 See the <a href="{@docRoot}/javax/management/MXBean.html#MXBean-spec"> |
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73 MXBean</a> specification for details. |
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74 |
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75 <h3><a id="examples">Ways to Access MXBeans</a></h3> |
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76 |
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77 <p>An application can monitor the instrumentation of the |
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78 Java virtual machine and the runtime in the following ways: |
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79 <p> |
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80 <b>1. Direct access to an MXBean interface</b> |
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81 <ul> |
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82 <li>Get an MXBean instance locally in the running Java virtual machine: |
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83 <pre> |
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84 RuntimeMXBean mxbean = ManagementFactory.getRuntimeMXBean(); |
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85 |
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86 // Get the standard attribute "VmVendor" |
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87 String vendor = mxbean.getVmVendor(); |
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88 </pre> |
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89 <p>Or by calling the |
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90 {@link java.lang.management.ManagementFactory#getPlatformMXBean(Class) |
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91 getPlatformMXBean} or |
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92 {@link java.lang.management.ManagementFactory#getPlatformMXBeans(Class) |
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93 getPlatformMXBeans} method: |
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94 <pre> |
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95 RuntimeMXBean mxbean = ManagementFactory.getPlatformMXBean(RuntimeMXBean.class); |
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96 |
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97 // Get the standard attribute "VmVendor" |
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98 String vendor = mxbean.getVmVendor(); |
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99 </pre> |
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100 </li> |
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101 <li>Construct an MXBean proxy instance that forwards the |
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102 method calls to a given MBeanServer: |
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103 <pre> |
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104 MBeanServerConnection mbs; |
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105 |
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106 // Connect to a running JVM (or itself) and get MBeanServerConnection |
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107 // that has the JVM MBeans registered in it |
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108 ... |
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109 |
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110 // Get a MBean proxy for RuntimeMXBean interface |
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111 RuntimeMXBean proxy = |
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112 {@link java.lang.management.ManagementFactory#getPlatformMXBean(MBeanServerConnection, Class) |
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113 ManagementFactory.getPlatformMXBean}(mbs, |
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114 RuntimeMXBean.class); |
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115 // Get standard attribute "VmVendor" |
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116 String vendor = proxy.getVmVendor(); |
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117 </pre> |
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118 <p>A proxy is typically used to access an MXBean |
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119 in a remote Java virtual machine. |
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120 An alternative way to create an MXBean proxy is: |
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121 <pre> |
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122 RuntimeMXBean proxy = |
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123 {@link java.lang.management.ManagementFactory#newPlatformMXBeanProxy |
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124 ManagementFactory.newPlatformMXBeanProxy}(mbs, |
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125 ManagementFactory.RUNTIME_MXBEAN_NAME, |
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126 RuntimeMXBean.class); |
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127 </pre> |
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128 </li> |
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129 </ul> |
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130 <p> |
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131 <b>2. Indirect access to an MXBean interface via MBeanServer</b> |
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132 <ul> |
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133 <li>Go through the |
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134 {@link java.lang.management.ManagementFactory#getPlatformMBeanServer |
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135 platform MBeanServer} to access MXBeans locally or |
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136 a specific {@code MBeanServerConnection} to access |
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137 MXBeans remotely. |
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138 The attributes and operations of an MXBean use only |
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139 <em>JMX open types</em> which include basic data types, |
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140 {@link javax.management.openmbean.CompositeData CompositeData}, |
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141 and {@link javax.management.openmbean.TabularData TabularData} |
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142 defined in {@link javax.management.openmbean.OpenType OpenType}. |
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143 <pre> |
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144 MBeanServerConnection mbs; |
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145 |
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146 // Connect to a running JVM (or itself) and get MBeanServerConnection |
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147 // that has the JVM MXBeans registered in it |
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148 ... |
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149 |
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150 try { |
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151 // Assuming the RuntimeMXBean has been registered in mbs |
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152 ObjectName oname = new ObjectName(ManagementFactory.RUNTIME_MXBEAN_NAME); |
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153 |
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154 // Get standard attribute "VmVendor" |
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155 String vendor = (String) mbs.getAttribute(oname, "VmVendor"); |
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156 } catch (....) { |
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157 // Catch the exceptions thrown by ObjectName constructor |
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158 // and MBeanServer.getAttribute method |
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159 ... |
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160 } |
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161 </pre> |
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162 </li> |
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163 </ul> |
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164 |
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165 |
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166 <h3><a id="extension">Platform Extension</a></h3> |
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167 |
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168 <p>A Java virtual machine implementation may add its platform extension to |
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169 the management interface by defining platform-dependent |
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170 interfaces that extend the standard management interfaces to include |
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171 platform-specific metrics and management operations. |
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172 The static factory methods in the <code>ManagementFactory</code> class will |
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173 return the MXBeans with the platform extension. |
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174 |
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175 <p> |
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176 It is recommended to name the platform-specific attributes with |
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177 a vendor-specific prefix such as the vendor's name to |
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178 avoid collisions of the attribute name between the future extension |
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179 to the standard management interface and the platform extension. |
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180 If the future extension to the standard management interface defines |
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181 a new attribute for a management interface and the attribute name |
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182 is happened to be same as some vendor-specific attribute's name, |
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183 the applications accessing that vendor-specific attribute would have |
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184 to be modified to cope with versioning and compatibility issues. |
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185 |
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186 <p>Below is an example showing how to access an attribute |
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187 from the platform extension: |
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188 |
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189 <p> |
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190 1) Direct access to the Oracle-specific MXBean interface |
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191 <blockquote> |
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192 <pre> |
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193 List<com.sun.management.GarbageCollectorMXBean> mxbeans = |
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194 ManagementFactory.getPlatformMXBeans(com.sun.management.GarbageCollectorMXBean.class); |
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195 |
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196 for (com.sun.management.GarbageCollectorMXBean gc : mxbeans) { |
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197 // Get the standard attribute "CollectionCount" |
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198 String count = mxbean.getCollectionCount(); |
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199 |
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200 // Get the platform-specific attribute "LastGcInfo" |
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201 GcInfo gcinfo = gc.getLastGcInfo(); |
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202 ... |
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203 } |
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204 </pre> |
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205 </blockquote> |
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206 |
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207 <p> |
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208 2) Access the Oracle-specific MXBean interface via <code>MBeanServer</code> |
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209 through proxy |
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210 |
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211 <blockquote><pre> |
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212 MBeanServerConnection mbs; |
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213 |
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214 // Connect to a running JVM (or itself) and get MBeanServerConnection |
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215 // that has the JVM MXBeans registered in it |
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216 ... |
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217 |
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218 List<com.sun.management.GarbageCollectorMXBean> mxbeans = |
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219 ManagementFactory.getPlatformMXBeans(mbs, com.sun.management.GarbageCollectorMXBean.class); |
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220 |
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221 for (com.sun.management.GarbageCollectorMXBean gc : mxbeans) { |
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222 // Get the standard attribute "CollectionCount" |
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223 String count = mxbean.getCollectionCount(); |
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224 |
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225 // Get the platform-specific attribute "LastGcInfo" |
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226 GcInfo gcinfo = gc.getLastGcInfo(); |
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227 ... |
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228 } |
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229 </pre></blockquote> |
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230 |
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231 <p> Unless otherwise noted, passing a <code>null</code> argument to a constructor |
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232 or method in any class or interface in this package will cause a {@link |
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233 java.lang.NullPointerException NullPointerException} to be thrown. |
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234 |
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235 <p> The java.lang.management API is thread-safe. |
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236 |
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237 @see {@linkplain javax.management JMX Specification} |
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238 |
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239 @author Mandy Chung |
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240 @since 1.5 |
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241 |
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242 </body> |
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243 </html> |