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<title>javax.management.openmbean package</title>
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<p>Provides the open data types and Open MBean descriptor classes.
An <em>Open MBean</em> is an MBean where the types of attributes
and of operation parameters and return values are built using a
small set of predefined Java classes. Open MBeans facilitate
operation with remote management programs that do not necessarily
have access to application-specific types, including non-Java
programs.</p>
<p>Every MBean has an {@link javax.management.MBeanInfo
MBeanInfo} with information about the MBean itself, and its
attributes, operations, constructors, and notifications. In an
Open MBean, this <code>MBeanInfo</code> implements the {@link
javax.management.openmbean.OpenMBeanInfo OpenMBeanInfo}
interface, usually by being an instance of {@link
javax.management.openmbean.OpenMBeanInfoSupport
OpenMBeanInfoSupport}.</p>
<p>The attribute information returned by {@link
javax.management.MBeanInfo#getAttributes()
MBeanInfo.getAttributes} for an Open MBean is an array of
objects implementing {@link
javax.management.openmbean.OpenMBeanAttributeInfo
OpenMBeanAttributeInfo}, usually instances of {@link
javax.management.openmbean.OpenMBeanAttributeInfoSupport
OpenMBeanAttributeInfoSupport}. In addition to the usual
information about attributes, an
<code>OpenMBeanAttributeInfo</code> specifies the {@link
javax.management.openmbean.OpenType OpenType} of the attribute.
The possible <code>OpenType</code> values are predefined, which
is what ensures that remote managers will understand them.</p>
<p>Similar remarks apply to the parameter types of operations and
constructors, and to the return types of operations.</p>
<p>There is a distinction between an attribute's Java language
type, as returned by {@link
javax.management.MBeanAttributeInfo#getType() getType()}, and
its <code>OpenType</code>, as returned by {@link
javax.management.openmbean.OpenMBeanAttributeInfo#getOpenType()
getOpenType()}. For example, if the Java language type is
<code>java.lang.String</code>, the <code>OpenType</code> will be
{@link javax.management.openmbean.SimpleType#STRING
SimpleType.String}. If the Java language type is {@link
javax.management.openmbean.CompositeData}, the
<code>OpenType</code> will be a {@link
javax.management.openmbean.CompositeType CompositeType} that
describes the items in the <code>CompositeData</code> instances
for the attribute.</p>
<h2><a name="constraints">Default values and constraints</a></h2>
<p>In Open MBeans, attributes and parameters can have default values
and/or constraints associated with them in the {@code
OpenMBeanAttributeInfo} or {@code OpenMBeanParameterInfo}.
There are two ways to specify these constraints. Either the
values are directly specified as parameters to one of the
constructors of {@code OpenMBeanAttributeInfoSupport} or
{@code OpenMBeanParameterInfoSupport}, for example
{@link
javax.management.openmbean.OpenMBeanParameterInfoSupport#OpenMBeanParameterInfoSupport(
String, String, OpenType, Object, Object[])}; or the values are
specified in a {@link javax.management.Descriptor Descriptor} given
as a parameter to one of the constructors.</p>
<p>When a {@code Descriptor} is used, the fields of interest are
these:</p>
<ul>
<li>{@code defaultValue} defines the value returned by
{@link javax.management.openmbean.OpenMBeanParameterInfo#getDefaultValue()
getDefaultValue()};
<li>{@code minValue} defines the value returned by {@link
javax.management.openmbean.OpenMBeanParameterInfo#getMinValue() getMinValue()};
<li>{@code maxValue} defines the value returned by {@link
javax.management.openmbean.OpenMBeanParameterInfo#getMaxValue() getMaxValue()};
<li>{@code legalValues} defines the values returned by {@link
javax.management.openmbean.OpenMBeanParameterInfo#getLegalValues() getLegalValues()}.
</ul>
<p>For {@code defaultValue}, {@code minValue}, and {@code
maxValue}, the associated value must either be of the Java type
corresponding to {@code openType}, or be a string that can be
converted into that type. The conversion uses the static method
{@code valueOf(String)} if it finds one; otherwise a constructor
with a single {@code String} parameter if it finds one; otherwise
it fails.</p>
<p>For {@code legalValues}, the associated value must be either
an array or a {@code Set}, and the elements of the array or set
must be convertible as described for {@code defaultValue} etc.</p>
<p>The following conditions must be met for these fields:</p>
<ul>
<li>the values must be of the appropriate type, or be strings
that can be converted to the appropriate type as explained
above;
<li>if {@code legalValues} is present then neither {@code
minValue} nor {@code maxValue} must be present;
<li>if {@code defaultValue} is present then it must satisfy the
constraints defined by {@code legalValues}, {@code minValue}, or
{@code maxValue} when any of these is also present;
<li>if {@code minValue} and {@code maxValue} are both present
then {@code minValue} must not be greater than {@code maxValue}.
</ul>
@see <a href="{@docRoot}/technotes/guides/jmx/">
Java Platform documentation on JMX technology</a>,
in particular the
<a href="{@docRoot}/technotes/guides/jmx/JMX_1_4_specification.pdf">
JMX Specification, version 1.4</a>
@since 1.5
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