Class CallMethodRule

java.lang.Object
org.apache.commons.digester.Rule
org.apache.commons.digester.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(java.lang.Object, java.lang.String, java.lang.Object) 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(java.lang.Object, java.lang.String, java.lang.Object) (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 Details

    • bodyText

      protected String bodyText
      The body text collected from this element.
    • targetOffset

      protected 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.
    • methodName

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

      protected boolean useExactMatch
      Should MethodUtils.invokeExactMethod be used for reflection.
  • Constructor Details

    • CallMethodRule

      @Deprecated public CallMethodRule(Digester digester, 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:
      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

      @Deprecated public CallMethodRule(Digester digester, String methodName, int paramCount, String[] paramTypes)
      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
      paramTypes - The Java class names of the arguments (if you wish to use a primitive type, specify the corresonding Java wrapper class instead, such as java.lang.Boolean for a boolean parameter)
    • CallMethodRule

      @Deprecated public CallMethodRule(Digester digester, String methodName, int paramCount, Class<?>[] paramTypes)
      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
      paramTypes - The Java classes that represent the parameter types of the method arguments (if you wish to use a primitive type, specify the corresonding Java wrapper class instead, such as java.lang.Boolean.TYPE for a boolean parameter)
    • 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(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(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(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(String methodName, int paramCount, String[] 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
      paramTypes - The Java class names of the arguments (if you wish to use a primitive type, specify the corresonding Java wrapper class instead, such as java.lang.Boolean for a boolean parameter)
    • CallMethodRule

      public CallMethodRule(int targetOffset, String methodName, int paramCount, String[] 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
      paramTypes - The Java class names of the arguments (if you wish to use a primitive type, specify the corresonding Java wrapper class instead, such as java.lang.Boolean for a boolean parameter)
    • CallMethodRule

      public CallMethodRule(String methodName, int paramCount, Class<?>[] 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
      paramTypes - The Java classes that represent the parameter types of the method arguments (if you wish to use a primitive type, specify the corresonding Java wrapper class instead, such as java.lang.Boolean.TYPE for a boolean parameter)
    • CallMethodRule

      public CallMethodRule(int targetOffset, String methodName, int paramCount, Class<?>[] 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
      paramTypes - The Java classes that represent the parameter types of the method arguments (if you wish to use a primitive type, specify the corresonding Java wrapper class instead, such as java.lang.Boolean.TYPE for a boolean parameter)
  • Method Details

    • getUseExactMatch

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

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

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

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

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

      public void end() throws Exception
      Process the end of this element.
      Overrides:
      end in class Rule
      Throws:
      Exception
    • finish

      public void finish() throws Exception
      Clean up after parsing is complete.
      Overrides:
      finish in class Rule
      Throws:
      Exception
    • 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
    • toString

      public String toString()
      Render a printable version of this Rule.
      Overrides:
      toString in class Object