Struts Double Range Field Validator Example

The double range field validator checks if a float/double field falls within a specified range. We can use this validator in either XML or annotation:

• • XML: specifying type=”double” attribute for <validator> or <field-validator> elements.
  • Annotation: specifying @DoubleRangeFieldValidator annotation type before field’s setter method or action method (plain-validator).

The range can be inclusive or exclusive. For example, if we specify a range of [10, 50] for a number x, then:

• • an inclusive range means: 10 <= x <= 50
  • an exclusive range means: 10 < x < 50

1. Struts Double Range Field Validator XML Syntax:

Usage:

• Field-validator syntax:
  

  <field name="fieldName">
  	<field-validator type="double">
  		<param name="param name">param value</param>
  		<message>validation error message</message>
  	</field-validator>
  </field>

   

• Plain-validator syntax:
  

  <validator type="double">
  		<param name="param name">param value</param>
  		<message>validation error message</message>
  </validator>  

Parameters:

Struts Double Range Field Validator XML Examples:

• Field-validator example using inclusive range check:

  <field name="scale">
  	<field-validator type="double">
  		<param name="minInclusive">0.5</param>
  		<param name="maxInclusive">10.5</param>
  		<message>The scale must bet between ${minInclusive} and ${maxInclusive} (inclusive)</message>
  	</field-validator>
  </field>

• Field-validator example using exclusive range check:

  <field name="scale">
  	<field-validator type="double">
  		<param name="minExclusive">0.5</param>
  		<param name="maxExclusive">10.5</param>
  		<message>The scale must be between ${minExclusive} and ${maxExclusive} (exclusive)</message>
  	</field-validator>
  </field>

• Only checking the minimum value:

  <field name="scale">
  	<field-validator type="double">
  		<param name="minInclusive">5.2</param>
  		<message>The scale must be equal or greater than ${minInclusive}</message>
  	</field-validator>
  </field>

• Using OGNL expressions:

  <field name="scale">
  	<field-validator type="double">
  		<param name="minExclusiveExpression">${minExclusiveValue}</param>
  		<param name="maxExclusiveExpression">${maxExclusiveValue}</param>
  		<message>The scale must be between ${minExclusive} and ${maxExclusive} (exclusive)</message>
  	</field-validator>
  </field> 

  In this case, the action class or the JavaBean class must implement the following methods (for example):

  public double getMinExclusiveValue() {
  	return 11.5;
  }
  
  public double getMaxExclusiveValue() {
  	return 40.3;
  } 

• Plain-validator example:
  

  <validator type="double">
  	<param name="fieldName">scale</param>
  	<param name="minInclusive">0.5</param>
  	<param name="maxInclusive">10.5</param>
  	<message>The scale must bet between ${minInclusive} and ${maxInclusive} (inclusive)</message>
  </validator> 

2. Struts @DoubleRangeFieldValidator Annotation

Usage: Put the @DoubleRangeFieldValidatorannotation before the setter method or action method (in case of using plain-validator) in the following form:

@DoubleRangeFieldValidator(param1 = "param 1 value", param2 = "param 2 value", ...)

Parameters:

Struts @DoubleRangeFieldValidator Examples:

• Basic field-validator:
  

  @DoubleRangeFieldValidator(
  		minInclusive = "23.5", maxInclusive = "57.8",
  		message = "The scale must bet between ${minInclusive} and ${maxInclusive} (inclusive)"
  		)
  public void setScale(double scale) {
  	this.scale = scale;
  }

   

• Specifying i18n key for the message:
  

  @DoubleRangeFieldValidator(
  		minInclusive = "23.5", maxInclusive = "57.8",
  		message = "Default message",
  		key = "form.validation.scale"
  		)
  public void setScale(double scale) {
  	this.scale = scale;
  }

   

• Plain-validator (annotating the action method):
  

  @DoubleRangeFieldValidator(
  		type = ValidatorType.SIMPLE,
  		fieldName = "scale",
  		minExclusive = "20.5",
  		maxExclusive = "78.5",
  		message = "The scale must be between ${minExclusive} and ${maxExclusive} (exclusive)"
  		)
  public String execute() {
  	return SUCCESS;
  } 

Related Struts Form Validation Tutorials:

• Struts Form Handling Tutorial
• Struts Form Validation Tutorial
• Struts Date Range Field Validator Example
• Struts Integer Range Field Validator Example
• Struts Short Range Field Validator Example
• Struts String Length Field Validator Example

Other Struts Tutorials:

• Introduction to Struts 2 framework
• Struts beginner tutorial (Eclipse + Tomcat + XML)
• Struts Beginner Tutorial with Annotations
• Struts beginner tutorial with Convention Plugin (zero-configuration)
• How to handle exceptions in Struts
• Send e-mail with attachments in Struts
• Struts File Upload Tutorial
• Struts - Spring - Hibernate Integration Tutorial

About the Author:

Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He began programming with Java back in the days of Java 1.4 and has been passionate about it ever since. You can connect with him on Facebook and watch his Java videos on YouTube.