io.permazen.util

Class ImplementationsReader

java.lang.Object

io.permazen.util.AbstractXMLStreaming

io.permazen.util.ImplementationsReader

public class ImplementationsReader
extends AbstractXMLStreaming

Scans the classpath and parses XML descriptor files describing implementation classes.

The XML files that this class parses look like this, for some value of foobar:

Example:

  <foobar-implementations>
      <foobar-implementation class="com.example.MyFoobarImplementation"/>
  </foobar-implementations>
 

Field Summary

Fields

Modifier and Type	Field and Description
protected Logger	log

Constructor Summary

Constructors

Constructor and Description
ImplementationsReader(String name) Constructor.

Method Summary

Modifier and Type	Method and Description
<T> List<T>	findImplementations(Class<T> type, String resource) Find all available implementations based on reading all XML files on the classpath at the specified resource name.
List<String>	parse(InputStream input) Parse the XML input and return the list of class names.
void	setConstructorParameterLists(List<Object[]> list) Configure constructor parameter lists.

Methods inherited from class io.permazen.util.AbstractXMLStreaming

expect, expectClose, getAttr, getAttr, getBooleanAttr, getBooleanAttr, getIntAttr, getIntAttr, getLongAttr, newInvalidAttributeException, next, skip, writeElement

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

log

protected final Logger log

Constructor Detail

ImplementationsReader

public ImplementationsReader(String name)

Constructor.

Parameters:

name - base name for XML tags (e.g., "foobar")

Throws:

IllegalArgumentException - if name is null

Method Detail

setConstructorParameterLists

public void setConstructorParameterLists(List<Object[]> list)

Configure constructor parameter lists.

By default, only default constructors are tried. This method allows configuring a list of possible constructors to try, by supplying corresponding parameter lists. The parameter lists will be tried in order.

If multiple constructors are compatible with a given parameter list, which one gets chosen is indeterminate.

Parameters:

list - list of constructor parameter lists to try

Throws:

IllegalArgumentException - if list is null

IllegalArgumentException - if list is empty

IllegalArgumentException - if list contains a null entry

parse

public List<String> parse(InputStream input)
                   throws XMLStreamException

Parse the XML input and return the list of class names.

Parameters:

input - XML input

Returns:

list of class names

Throws:

IllegalArgumentException - if input is null

XMLStreamException - if XML parse fails

findImplementations

public <T> List<T> findImplementations(Class<T> type,
                                       String resource)

Find all available implementations based on reading all XML files on the classpath at the specified resource name.

If any errors occur, they are logged but otherwise ignored.

Type Parameters:

T - implementation type

Parameters:

type - required implementation type

resource - XML file classpath resource

Returns:

list of instantiated implementations

Throws:

IllegalArgumentException - if either parameter is null