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date Sat, 01 Dec 2007 00:00:00 +0000
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1 <html>
2 <head>
3 <title>javax.management.openmbean package</title>
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30
31 <p>Provides the open data types and Open MBean descriptor classes.
32 An <em>Open MBean</em> is an MBean where the types of attributes
33 and of operation parameters and return values are built using a
34 small set of predefined Java classes. Open MBeans facilitate
35 operation with remote management programs that do not necessarily
36 have access to application-specific types, including non-Java
37 programs.</p>
38
39 <p>Every MBean has an {@link javax.management.MBeanInfo
40 MBeanInfo} with information about the MBean itself, and its
41 attributes, operations, constructors, and notifications. In an
42 Open MBean, this <code>MBeanInfo</code> implements the {@link
43 javax.management.openmbean.OpenMBeanInfo OpenMBeanInfo}
44 interface, usually by being an instance of {@link
45 javax.management.openmbean.OpenMBeanInfoSupport
46 OpenMBeanInfoSupport}.</p>
47
48 <p>The attribute information returned by {@link
49 javax.management.MBeanInfo#getAttributes()
50 MBeanInfo.getAttributes} for an Open MBean is an array of
51 objects implementing {@link
52 javax.management.openmbean.OpenMBeanAttributeInfo
53 OpenMBeanAttributeInfo}, usually instances of {@link
54 javax.management.openmbean.OpenMBeanAttributeInfoSupport
55 OpenMBeanAttributeInfoSupport}. In addition to the usual
56 information about attributes, an
57 <code>OpenMBeanAttributeInfo</code> specifies the {@link
58 javax.management.openmbean.OpenType OpenType} of the attribute.
59 The possible <code>OpenType</code> values are predefined, which
60 is what ensures that remote managers will understand them.</p>
61
62 <p>Similar remarks apply to the parameter types of operations and
63 constructors, and to the return types of operations.</p>
64
65 <p>There is a distinction between an attribute's Java language
66 type, as returned by {@link
67 javax.management.MBeanAttributeInfo#getType() getType()}, and
68 its <code>OpenType</code>, as returned by {@link
69 javax.management.openmbean.OpenMBeanAttributeInfo#getOpenType()
70 getOpenType()}. For example, if the Java language type is
71 <code>java.lang.String</code>, the <code>OpenType</code> will be
72 {@link javax.management.openmbean.SimpleType#STRING
73 SimpleType.String}. If the Java language type is {@link
74 javax.management.openmbean.CompositeData}, the
75 <code>OpenType</code> will be a {@link
76 javax.management.openmbean.CompositeType CompositeType} that
77 describes the items in the <code>CompositeData</code> instances
78 for the attribute.</p>
79
80 <h2><a name="constraints">Default values and constraints</a></h2>
81
82 <p>In Open MBeans, attributes and parameters can have default values
83 and/or constraints associated with them in the {@code
84 OpenMBeanAttributeInfo} or {@code OpenMBeanParameterInfo}.
85 There are two ways to specify these constraints. Either the
86 values are directly specified as parameters to one of the
87 constructors of {@code OpenMBeanAttributeInfoSupport} or
88 {@code OpenMBeanParameterInfoSupport}, for example
89 {@link
90 javax.management.openmbean.OpenMBeanParameterInfoSupport#OpenMBeanParameterInfoSupport(
91 String, String, OpenType, Object, Object[])}; or the values are
92 specified in a {@link javax.management.Descriptor Descriptor} given
93 as a parameter to one of the constructors.</p>
94
95 <p>When a {@code Descriptor} is used, the fields of interest are
96 these:</p>
97
98 <ul>
99
100 <li>{@code defaultValue} defines the value returned by
101 {@link javax.management.openmbean.OpenMBeanParameterInfo#getDefaultValue()
102 getDefaultValue()};
103
104 <li>{@code minValue} defines the value returned by {@link
105 javax.management.openmbean.OpenMBeanParameterInfo#getMinValue() getMinValue()};
106
107 <li>{@code maxValue} defines the value returned by {@link
108 javax.management.openmbean.OpenMBeanParameterInfo#getMaxValue() getMaxValue()};
109
110 <li>{@code legalValues} defines the values returned by {@link
111 javax.management.openmbean.OpenMBeanParameterInfo#getLegalValues() getLegalValues()}.
112
113 </ul>
114
115 <p>For {@code defaultValue}, {@code minValue}, and {@code
116 maxValue}, the associated value must either be of the Java type
117 corresponding to {@code openType}, or be a string that can be
118 converted into that type. The conversion uses the static method
119 {@code valueOf(String)} if it finds one; otherwise a constructor
120 with a single {@code String} parameter if it finds one; otherwise
121 it fails.</p>
122
123 <p>For {@code legalValues}, the associated value must be either
124 an array or a {@code Set}, and the elements of the array or set
125 must be convertible as described for {@code defaultValue} etc.</p>
126
127 <p>The following conditions must be met for these fields:</p>
128
129 <ul>
130 <li>the values must be of the appropriate type, or be strings
131 that can be converted to the appropriate type as explained
132 above;
133
134 <li>if {@code legalValues} is present then neither {@code
135 minValue} nor {@code maxValue} must be present;
136
137 <li>if {@code defaultValue} is present then it must satisfy the
138 constraints defined by {@code legalValues}, {@code minValue}, or
139 {@code maxValue} when any of these is also present;
140
141 <li>if {@code minValue} and {@code maxValue} are both present
142 then {@code minValue} must not be greater than {@code maxValue}.
143 </ul>
144
145 @see <a href="{@docRoot}/../technotes/guides/jmx/">
146 Java SE 6 Platform documentation on JMX technology</a>,
147 in particular the
148 <a href="{@docRoot}/../technotes/guides/jmx/JMX_1_4_specification.pdf">
149 JMX Specification, version 1.4</a>
150
151 @since 1.5
152
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