java.lang.Object
- java.lang.ClassLoader
- - com.wolfram.jlink.JLinkClassLoader

```
public class JLinkClassLoader
extends java.lang.ClassLoader
```
This class loader does all the loading of classes requested via the Mathematica function LoadJavaClass[]. It also loads native libraries and resources used by classes that it loads. The directories and files it searches for classes and other resources are provided to it via the addLocations() method, which is called from Mathematica during every call to LoadJavaClass[] and also by AddToClassPath[]. The JLink Mathematica code manages the class path locations, including providing a default set of extra dirs. Directories are automatically searched for jar or zip files they contain, so you do not have to name jar files explicitly in addLocations(), although you can if you want to limit the search to a specific jar file in a directory.
Most uses of this class are internal to J/Link, and most programmers will never deal with it directly. One reason to use this class is if you want to load a class in Java code that is found in the special set of extra locations that this class loader knows about (such as Java subdirectories of Mathematica application directories). Each KernelLink has a JLinkClassLoader instance associated with it, which you can retrieve using the link's getClassLoader() method. Here is an example of loading a class from a special J/Link-specific directory.
```
 Class cls = Class.forName("Some.class.that.only.JLink.can.find", ml.getClassLoader());
```
You can add directories and jar files to the search path using the addLocations() method:
```
 // This is equivalent to calling AddToClassPath["/some/dir", "/another/dir"] in Mathematica.
 ml.getClassLoader().addLocations(new String[]{"/some/dir", "/another/dir"}, true);
```
If you using this class from a standalone Java program you should first call the KernelLink method enableObjectReferences() to initialize the class loader with the special Mathematica-specific locations for Java classes.
Another advanced reason to use this class is if you need the class loader to have a specific parent loader, because that parent loader has certain capabilities or can load classes from certain locations that J/Link would otherwise not know about.
```
 KernelLink ml = MathLinkFactory.createKernelLink(...);
 ml.discardAnswer();
 ml.setClassLoader(new JLinkClassLoader(mySpecialParentClassLoader));
 ml.enableObjectReferences();
```
The class has some static methods that are intended to be used from Mathematica code. Here is an example that loads a resource from a Mathematica application's Java subdirectory:
```
 (* Mathematica code *)
 LoadJavaClass["com.wolfram.jlink.JLinkClassLoader"];
 JLinkClassLoader`getInstance[]@getResource["myImage.gif"];
```
When using the class from Java, you will always have a specific link in hand, so instead of calling static methods you should obtain a JLinkClassLoader instance from the link using its getClassLoader() method and then call instance methods.
Since:

3.0

See Also:

KernelLink.getClassLoader(), KernelLink.setClassLoader(JLinkClassLoader)

Field Summary

Fields
Modifier and Type Field Description

protected com.wolfram.jlink.JLinkClassLoaderHelper helper

Constructor Summary

Constructors
Constructor	Description
`JLinkClassLoader()`	Constructs a new JLinkClassLoader instance.
`JLinkClassLoader(java.lang.ClassLoader parent)`	Constructs a new JLinkClassLoader instance that has the given class loader as its parent loader.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`protected void`	`addAll(java.util.List<java.net.URL> urlsToAdd, boolean prepend)`
`void`	`addLocations(java.lang.String[] locations, boolean searchForJars)`	Adds URLs, directories, and jar files in which this classloader will look for classes.
`void`	`addLocations(java.lang.String[] locations, boolean searchForJars, boolean prepend)`
`java.lang.Class<?>`	`classFromBytes(java.lang.String className, byte[] bytes)`	Converts an array of bytes into an instance of class Class.
`static java.lang.Class<?>`	`classFromName(java.lang.String name)`	Loads the class with the given name using the JLinkClassLoader instance of the currently-active link.
`void`	`clearAssertionStatus()`
`static JLinkClassLoader`	`createClassLoader()`	This factory method is the proper way to create a JLinkClassLoader instance, rather than directly calling the constructor.
`java.lang.String[]`	`getClassPath()`	Gives the set of locations in which this class loader will search for classes.
`static JLinkClassLoader`	`getInstance()`	Retrieves the JLinkClassLoader instance being used by the currently-active link.
`java.net.URL`	`getResource(java.lang.String name)`
`java.io.InputStream`	`getResourceAsStream(java.lang.String name)`
`java.util.Enumeration<java.net.URL>`	`getResources(java.lang.String name)`
`java.lang.Class<?>`	`loadClass(java.lang.String name)`
`void`	`setClassAssertionStatus(java.lang.String className, boolean enabled)`
`void`	`setDefaultAssertionStatus(boolean enabled)`
`void`	`setPackageAssertionStatus(java.lang.String packageName, boolean enabled)`

Methods inherited from class java.lang.ClassLoader
defineClass, defineClass, defineClass, defineClass, definePackage, findClass, findClass, findLibrary, findLoadedClass, findResource, findResource, findResources, findSystemClass, getClassLoadingLock, getDefinedPackage, getDefinedPackages, getName, getPackage, getPackages, getParent, getPlatformClassLoader, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, getUnnamedModule, isRegisteredAsParallelCapable, loadClass, registerAsParallelCapable, resolveClass, resources, setSigners

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - helper
```
protected volatile com.wolfram.jlink.JLinkClassLoaderHelper helper
```
- Constructor Detail
  - JLinkClassLoader
```
public JLinkClassLoader()
```
    Constructs a new JLinkClassLoader instance. Only advanced programmers will need to use this.
    
    Since:
    
    3.0
  - JLinkClassLoader
```
public JLinkClassLoader(java.lang.ClassLoader parent)
```
    Constructs a new JLinkClassLoader instance that has the given class loader as its parent loader. Only advanced programmers will need to use this.
    
    Since:
    
    3.0
- Method Detail
  - clearAssertionStatus
```
public void clearAssertionStatus()
```
    Overrides:
    
    clearAssertionStatus in class java.lang.ClassLoader
  - setClassAssertionStatus
```
public void setClassAssertionStatus(java.lang.String className,
                                    boolean enabled)
```
    Overrides:
    
    setClassAssertionStatus in class java.lang.ClassLoader
  - setDefaultAssertionStatus
```
public void setDefaultAssertionStatus(boolean enabled)
```
    Overrides:
    
    setDefaultAssertionStatus in class java.lang.ClassLoader
  - setPackageAssertionStatus
```
public void setPackageAssertionStatus(java.lang.String packageName,
                                      boolean enabled)
```
    Overrides:
    
    setPackageAssertionStatus in class java.lang.ClassLoader
  - getResource
```
public java.net.URL getResource(java.lang.String name)
```
    Overrides:
    
    getResource in class java.lang.ClassLoader
  - getResources
```
public java.util.Enumeration<java.net.URL> getResources(java.lang.String name)
                                                 throws java.io.IOException
```
    Overrides:
    
    getResources in class java.lang.ClassLoader
    
    Throws:
    
    java.io.IOException
  - getResourceAsStream
```
public java.io.InputStream getResourceAsStream(java.lang.String name)
```
    Overrides:
    
    getResourceAsStream in class java.lang.ClassLoader
  - loadClass
```
public java.lang.Class<?> loadClass(java.lang.String name)
                             throws java.lang.ClassNotFoundException
```
    Overrides:
    
    loadClass in class java.lang.ClassLoader
    
    Throws:
    
    java.lang.ClassNotFoundException
  - createClassLoader
```
public static JLinkClassLoader createClassLoader()
```
    This factory method is the proper way to create a JLinkClassLoader instance, rather than directly calling the constructor. In Java 9 and later, this will return an instance of JLinkClassLoader9, a subclass that has special capabilities to support ExternalEvaluate functionality in WL.
    
    Returns:
    
    the newly-created JLinkClassLoader
  - getInstance
```
public static JLinkClassLoader getInstance()
```
    Retrieves the JLinkClassLoader instance being used by the currently-active link. This method is intended to be called only from Mathematica, where the "active link" is well-defined (it is the link on which the call is coming in on).
    
    Since:
    
    3.0
  - classFromName
```
public static java.lang.Class<?> classFromName(java.lang.String name)
                                        throws java.lang.ClassNotFoundException
```
    Loads the class with the given name using the JLinkClassLoader instance of the currently-active link. This method is intended to be called only from Mathematica, where the "active link" is well-defined (it is the link on which the call is coming in on).
    
    Throws:
    
    java.lang.ClassNotFoundException
    
    Since:
    
    3.0
  - addLocations
```
public void addLocations(java.lang.String[] locations,
                         boolean searchForJars)
```
    Adds URLs, directories, and jar files in which this classloader will look for classes. The elements of the locations array must be full paths to directories or jar or zip files, or http URLs. The searchForJars parameter determines whether directories will be automatically searched for any jar files they contain.
    
    Since:
    
    3.0
  - addLocations
```
public void addLocations(java.lang.String[] locations,
                         boolean searchForJars,
                         boolean prepend)
```
  - getClassPath
```
public java.lang.String[] getClassPath()
```
    Gives the set of locations in which this class loader will search for classes. Only the locations known by this loader, not its parent loader, are returned.
    
    Since:
    
    3.0
  - classFromBytes
```
public java.lang.Class<?> classFromBytes(java.lang.String className,
                                         byte[] bytes)
```
    Converts an array of bytes into an instance of class Class. This method is effectively a public export of the final ClassLoader method defineClass(). It exists mainly for future internal uses within J/Link applications.
    
    Since:
    
    3.0
  - addAll
```
protected void addAll(java.util.List<java.net.URL> urlsToAdd,
                      boolean prepend)
```

Class JLinkClassLoader

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.ClassLoader

Methods inherited from class java.lang.Object

Field Detail

helper

Constructor Detail

JLinkClassLoader

JLinkClassLoader

Method Detail

clearAssertionStatus

setClassAssertionStatus

setDefaultAssertionStatus

setPackageAssertionStatus

getResource

getResources

getResourceAsStream

loadClass

createClassLoader

getInstance

classFromName

addLocations

addLocations

getClassPath

classFromBytes

addAll