org.apache.commons.digester

Class CallMethodRule


public class CallMethodRule
extends Rule

Rule implementation that calls a method on an object on the stack (normally the top/parent object), passing arguments collected from subsequent CallParamRule rules or from the body of this element.

By using CallMethodRule(String methodName) a method call can be made to a method which accepts no arguments.

Incompatible method parameter types are converted using org.apache.commons.beanutils.ConvertUtils.

This rule now uses MethodUtils.invokeMethod by default. This increases the kinds of methods successfully and allows primitives to be matched by passing in wrapper classes. There are rare cases when MethodUtils.invokeExactMethod (the old default) is required. This method is much stricter in it's reflection. Setting the UseExactMatch to true reverts to the use of this method.

Note that the target method is invoked when the end of the tag the CallMethodRule fired on is encountered, not when the last parameter becomes available. This implies that rules which fire on tags nested within the one associated with the CallMethodRule will fire before the CallMethodRule invokes the target method. This behaviour is not configurable.

Note also that if a CallMethodRule is expecting exactly one parameter and that parameter is not available (eg CallParamRule is used with an attribute name but the attribute does not exist) then the method will not be invoked. If a CallMethodRule is expecting more than one parameter, then it is always invoked, regardless of whether the parameters were available or not; missing parameters are converted to the appropriate target type by calling ConvertUtils.convert. Note that the default ConvertUtils converters for the String type returns a null when passed a null, meaning that CallMethodRule will passed null for all String parameters for which there is no parameter info available from the XML. However parameters of type Float and Integer will be passed a real object containing a zero value as that is the output of the default ConvertUtils converters for those types when passed a null. You can register custom converters to change this behaviour; see the beautils library documentation for more info.

Note that when a constructor is used with paramCount=0, indicating that the body of the element is to be passed to the target method, an empty element will cause an empty string to be passed to the target method, not null. And if automatic type conversion is being applied (ie if the target function takes something other than a string as a parameter) then the conversion will fail if the converter class does not accept an empty string as valid input.

CallMethodRule has a design flaw which can cause it to fail under certain rule configurations. All CallMethodRule instances share a single parameter stack, and all CallParamRule instances simply store their data into the parameter-info structure that is on the top of the stack. This means that two CallMethodRule instances cannot be associated with the same pattern without getting scrambled parameter data. This same issue also applies when a CallMethodRule matches some element X, a different CallMethodRule matches a child element Y and some of the CallParamRules associated with the first CallMethodRule match element Y or one of its child elements. This issue has been present since the very first release of Digester. Note, however, that this configuration of CallMethodRule instances is not commonly required.

Field Summary

protected String
bodyText
The body text collected from this element.
protected String
methodName
The method name to call on the parent object.
private String[]
paramClassNames
The names of the classes of the parameters to be collected.
protected int
paramCount
The number of parameters to collect from MethodParam rules.
protected Class[]
paramTypes
The parameter types of the parameters to be collected.
private int
targetOffset
location of the target object for the call, relative to the top of the digester object stack.
protected boolean
useExactMatch
Should MethodUtils.invokeExactMethod be used for reflection.

Fields inherited from class org.apache.commons.digester.Rule

digester, namespaceURI

Constructor Summary

CallMethodRule(String methodName)
Construct a "call method" rule with the specified method name.
CallMethodRule(String methodName, int paramCount)
Construct a "call method" rule with the specified method name.
CallMethodRule(String methodName, int paramCount, paramTypes[] )
Construct a "call method" rule with the specified method name and parameter types.
CallMethodRule(String methodName, int paramCount, paramTypes[] )
Construct a "call method" rule with the specified method name and parameter types.
CallMethodRule(int targetOffset, String methodName)
Construct a "call method" rule with the specified method name.
CallMethodRule(int targetOffset, String methodName, int paramCount)
Construct a "call method" rule with the specified method name.
CallMethodRule(int targetOffset, String methodName, int paramCount, paramTypes[] )
Construct a "call method" rule with the specified method name and parameter types.
CallMethodRule(int targetOffset, String methodName, int paramCount, paramTypes[] )
Construct a "call method" rule with the specified method name and parameter types.
CallMethodRule(Digester digester, String methodName, int paramCount)
Deprecated. The digester instance is now set in the Digester.addRule(String,Rule) method.
CallMethodRule(Digester digester, String methodName, int paramCount, paramTypes[] )
Deprecated. The digester instance is now set in the Digester.addRule(String,Rule) method.
CallMethodRule(Digester digester, String methodName, int paramCount, paramTypes[] )
Deprecated. The digester instance is now set in the Digester.addRule(String,Rule) method.

Method Summary

void
begin(Attributes attributes)
Process the start of this element.
void
body(String bodyText)
Process the body text of this element.
void
end()
Process the end of this element.
void
finish()
Clean up after parsing is complete.
boolean
getUseExactMatch()
Should MethodUtils.invokeExactMethod be used for the reflection.
protected void
processMethodCallResult(Object result)
Subclasses may override this method to perform additional processing of the invoked method's result.
void
setDigester(Digester digester)
Set the associated digester.
void
setUseExactMatch(boolean useExactMatch)
Set whether MethodUtils.invokeExactMethod should be used for the reflection.
String
toString()
Render a printable version of this Rule.

Methods inherited from class org.apache.commons.digester.Rule

begin, begin, body, body, end, end, finish, getDigester, getNamespaceURI, setDigester, setNamespaceURI

Field Details

bodyText

protected String bodyText
The body text collected from this element.

methodName

protected String methodName
The method name to call on the parent object.

paramClassNames

private String[] paramClassNames
The names of the classes of the parameters to be collected. This attribute allows creation of the classes to be postponed until the digester is set.

paramCount

protected int paramCount
The number of parameters to collect from MethodParam rules. If this value is zero, a single parameter will be collected from the body of this element.

paramTypes

protected Class[] paramTypes
The parameter types of the parameters to be collected.

targetOffset

private int targetOffset
location of the target object for the call, relative to the top of the digester object stack. The default value of zero means the target object is the one on top of the stack.

useExactMatch

protected boolean useExactMatch
Should MethodUtils.invokeExactMethod be used for reflection.

Constructor Details

CallMethodRule

public CallMethodRule(String methodName)
Construct a "call method" rule with the specified method name. The method should accept no parameters.
Parameters:
methodName - Method name of the parent method to call

CallMethodRule

public CallMethodRule(String methodName,
                      int paramCount)
Construct a "call method" rule with the specified method name. The parameter types (if any) default to java.lang.String.
Parameters:
methodName - Method name of the parent method to call
paramCount - The number of parameters to collect, or zero for a single argument from the body of this element.

CallMethodRule

public CallMethodRule(String methodName,
                      int paramCount,
                      paramTypes[] )
Construct a "call method" rule with the specified method name and parameter types. If paramCount is set to zero the rule will use the body of this element as the single argument of the method, unless paramTypes is null or empty, in this case the rule will call the specified method with no arguments.
Parameters:
methodName - Method name of the parent method to call
paramCount - The number of parameters to collect, or zero for a single argument from the body of ths element

CallMethodRule

public CallMethodRule(String methodName,
                      int paramCount,
                      paramTypes[] )
Construct a "call method" rule with the specified method name and parameter types. If paramCount is set to zero the rule will use the body of this element as the single argument of the method, unless paramTypes is null or empty, in this case the rule will call the specified method with no arguments.
Parameters:
methodName - Method name of the parent method to call
paramCount - The number of parameters to collect, or zero for a single argument from the body of ths element

CallMethodRule

public CallMethodRule(int targetOffset,
                      String methodName)
Construct a "call method" rule with the specified method name. The method should accept no parameters.
Parameters:
targetOffset - location of the target object. Positive numbers are relative to the top of the digester object stack. Negative numbers are relative to the bottom of the stack. Zero implies the top object on the stack.
methodName - Method name of the parent method to call

CallMethodRule

public CallMethodRule(int targetOffset,
                      String methodName,
                      int paramCount)
Construct a "call method" rule with the specified method name. The parameter types (if any) default to java.lang.String.
Parameters:
targetOffset - location of the target object. Positive numbers are relative to the top of the digester object stack. Negative numbers are relative to the bottom of the stack. Zero implies the top object on the stack.
methodName - Method name of the parent method to call
paramCount - The number of parameters to collect, or zero for a single argument from the body of this element.

CallMethodRule

public CallMethodRule(int targetOffset,
                      String methodName,
                      int paramCount,
                      paramTypes[] )
Construct a "call method" rule with the specified method name and parameter types. If paramCount is set to zero the rule will use the body of this element as the single argument of the method, unless paramTypes is null or empty, in this case the rule will call the specified method with no arguments.
Parameters:
targetOffset - location of the target object. Positive numbers are relative to the top of the digester object stack. Negative numbers are relative to the bottom of the stack. Zero implies the top object on the stack.
methodName - Method name of the parent method to call
paramCount - The number of parameters to collect, or zero for a single argument from the body of ths element

CallMethodRule

public CallMethodRule(int targetOffset,
                      String methodName,
                      int paramCount,
                      paramTypes[] )
Construct a "call method" rule with the specified method name and parameter types. If paramCount is set to zero the rule will use the body of this element as the single argument of the method, unless paramTypes is null or empty, in this case the rule will call the specified method with no arguments.
Parameters:
targetOffset - location of the target object. Positive numbers are relative to the top of the digester object stack. Negative numbers are relative to the bottom of the stack. Zero implies the top object on the stack.
methodName - Method name of the parent method to call
paramCount - The number of parameters to collect, or zero for a single argument from the body of ths element

CallMethodRule

public CallMethodRule(Digester digester,
                      String methodName,
                      int paramCount)

Deprecated. The digester instance is now set in the Digester.addRule(String,Rule) method. Use CallMethodRule(String methodName,int paramCount) instead.

Construct a "call method" rule with the specified method name. The parameter types (if any) default to java.lang.String.
Parameters:
digester - The associated Digester
methodName - Method name of the parent method to call
paramCount - The number of parameters to collect, or zero for a single argument from the body of this element.

CallMethodRule

public CallMethodRule(Digester digester,
                      String methodName,
                      int paramCount,
                      paramTypes[] )

Deprecated. The digester instance is now set in the Digester.addRule(String,Rule) method. Use CallMethodRule(String methodName,int paramCount, String [] paramTypes) instead.

Construct a "call method" rule with the specified method name.
Parameters:
digester - The associated Digester
methodName - Method name of the parent method to call
paramCount - The number of parameters to collect, or zero for a single argument from the body of ths element

CallMethodRule

public CallMethodRule(Digester digester,
                      String methodName,
                      int paramCount,
                      paramTypes[] )

Deprecated. The digester instance is now set in the Digester.addRule(String,Rule) method. Use CallMethodRule(String methodName,int paramCount, Class [] paramTypes) instead.

Construct a "call method" rule with the specified method name.
Parameters:
digester - The associated Digester
methodName - Method name of the parent method to call
paramCount - The number of parameters to collect, or zero for a single argument from the body of ths element

Method Details

begin

public void begin(Attributes attributes)
            throws Exception
Process the start of this element.
Overrides:
begin in interface Rule
Parameters:
attributes - The attribute list for this element

body

public void body(String bodyText)
            throws Exception
Process the body text of this element.
Overrides:
body in interface Rule
Parameters:
bodyText - The body text of this element

end

public void end()
            throws Exception
Process the end of this element.
Overrides:
end in interface Rule

finish

public void finish()
            throws Exception
Clean up after parsing is complete.
Overrides:
finish in interface Rule

getUseExactMatch

public boolean getUseExactMatch()
Should MethodUtils.invokeExactMethod be used for the reflection.

processMethodCallResult

protected void processMethodCallResult(Object result)
Subclasses may override this method to perform additional processing of the invoked method's result.
Parameters:
result - the Object returned by the method invoked, possibly null

setDigester

public void setDigester(Digester digester)
Set the associated digester. If needed, this class loads the parameter classes from their names.
Overrides:
setDigester in interface Rule

setUseExactMatch

public void setUseExactMatch(boolean useExactMatch)
Set whether MethodUtils.invokeExactMethod should be used for the reflection.

toString

public String toString()
Render a printable version of this Rule.

Copyright 2001-2005 The Apache Software Foundation.