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java.lang.Object | +--java.lang.Package
Package
objects contain version information
about the implementation and specification of a Java package.
This versioning information is retrieved and made available
by the classloader that loaded the class(es). Typically, it is
stored in the manifest that is distributed with the classes.
The set of classes that make up the package may implement a
particular specification and if
so the specification title, version number, and vendor strings
identify that specification.
An application can ask if the package is
compatible with a particular version, see the isCompatibleWith
method for details.
Specification version numbers use a "Dewey Decimal" syntax that consists of positive decimal integers separated by periods ".", for example, "2.0" or "1.2.3.4.5.6.7". This allows an extensible number to be used to represent major, minor, micro, etc versions. The version number must begin with a number.
The implementation title, version, and vendor strings identify an implementation and are made available conveniently to enable accurate reporting of the packages involved when a problem occurs. The contents all three implementation strings are vendor specific. The implementation version strings have no specified syntax and should only be compared for equality with desired version identifers. Within each classloader all classes from the same java package have the same Package object. The static methods allow a package to be found by name or the set of all packages known to the current class loader to be found.
ClassLoader.definePackage(java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.lang.String, java.net.URL)
Field Summary | |
private String |
implTitle
|
private String |
implVendor
|
private String |
implVersion
|
private static Map |
mans
|
private String |
pkgName
|
private static Map |
pkgs
|
private java.net.URL |
sealBase
|
private String |
specTitle
|
private String |
specVendor
|
private String |
specVersion
|
private static Map |
urls
|
Constructor Summary | |
private |
Package(String name,
java.util.jar.Manifest man,
java.net.URL url)
|
(package private) |
Package(String name,
String spectitle,
String specversion,
String specvendor,
String impltitle,
String implversion,
String implvendor,
java.net.URL sealbase)
Construct a package instance with the specified version information. |
Method Summary | |
private static Package |
defineSystemPackage(String iname,
String fn)
|
String |
getImplementationTitle()
Return the title of this package. |
String |
getImplementationVendor()
Returns the name of the organization, vendor or company that provided this implementation. |
String |
getImplementationVersion()
Return the version of this implementation. |
String |
getName()
Return the name of this package. |
(package private) static Package |
getPackage(Class c)
Get the package for the specified class. |
static Package |
getPackage(String name)
Find a package by name in the callers classloader. |
static Package[] |
getPackages()
Get all the packages currently known for the caller's class loader. |
String |
getSpecificationTitle()
Return the title of the specification that this package implements. |
String |
getSpecificationVendor()
Return the name of the organization, vendor, or company that owns and maintains the specification of the classes that implement this package. |
String |
getSpecificationVersion()
Returns the version number of the specification that this package implements. |
(package private) static Package |
getSystemPackage(String name)
|
private static String |
getSystemPackage0(String name)
|
(package private) static Package[] |
getSystemPackages()
|
private static String[] |
getSystemPackages0()
|
int |
hashCode()
Return the hashcode computed from the package name. |
boolean |
isCompatibleWith(String desired)
Compare this package's specification version with a desired version. |
boolean |
isSealed()
Returns true if this package is sealed. |
boolean |
isSealed(java.net.URL url)
Returns true if this package is sealed with respect to the specified code source url. |
private static java.util.jar.Manifest |
loadManifest(String fn)
|
String |
toString()
Returns the string representation of this Package. |
Methods inherited from class java.lang.Object |
|
Field Detail |
private static Map pkgs
private static Map urls
private static Map mans
private String pkgName
private String specTitle
private String specVersion
private String specVendor
private String implTitle
private String implVersion
private String implVendor
private java.net.URL sealBase
Constructor Detail |
Package(String name, String spectitle, String specversion, String specvendor, String impltitle, String implversion, String implvendor, java.net.URL sealbase)
pkgName
- the name of the packagespectitle
- the title of the specificationspecversion
- the version of the specificationspecvendor
- the organization that maintains the specificationimpltitle
- the title of the implementationimplversion
- the version of the implementationimplvendor
- the organization that maintains the implementationprivate Package(String name, java.util.jar.Manifest man, java.net.URL url)
Method Detail |
public String getName()
public String getSpecificationTitle()
public String getSpecificationVersion()
public String getSpecificationVendor()
public String getImplementationTitle()
public String getImplementationVersion()
public String getImplementationVendor()
public boolean isSealed()
public boolean isSealed(java.net.URL url)
url
- the code source urlpublic boolean isCompatibleWith(String desired) throws NumberFormatException
Version numbers are compared by sequentially comparing corresponding components of the desired and specification strings. Each component is converted as a decimal integer and the values compared. If the specification value is greater than the desired value true is returned. If the value is less false is returned. If the values are equal the period is skipped and the next pair of components is compared.
desired
- the version string of the desired version.public static Package getPackage(String name)
Packages have attributes for versions and specifications only if the class loader created the package instance with the appropriate attributes. Typically, those attributes are defined in the manifests that accompany the classes.
packageName
- a package name, for example, java.lang.public static Package[] getPackages()
null
in some implementations, only packages corresponding
to classes loaded by the bootstrap class loader will be returned.static Package getPackage(Class c)
null
in some implementations, then the set of packages
loaded by the bootstrap class loader is searched to find the package.
Packages have attributes for versions and specifications only if the class loader created the package instance with the appropriate attributes. Typically those attributes are defined in the manifests that accompany the classes.
class
- the class to get the package of.public int hashCode()
public String toString()
static Package getSystemPackage(String name)
static Package[] getSystemPackages()
private static Package defineSystemPackage(String iname, String fn)
private static java.util.jar.Manifest loadManifest(String fn)
private static String getSystemPackage0(String name)
private static String[] getSystemPackages0()
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