Archive for the ‘Development’ Category

Using Oracle’s SYS_GUID()

Friday, April 29th, 2011

Background

For years I’ve bemoaned Oracle’s lack of an auto-number/identity type column (think MySQL AUTO_INCREMENT). Obviously you can create sequences and triggers to produce the same effect but it always seemed like a bit of a palaver to me.

So, I had a smile on my when I discovered the delight that is SYS_GUID().

Taken from the Oracle documentation:

SYS_GUID generates and returns a globally unique identifier (RAW value) made up of 16 bytes. On most platforms, the generated identifier consists of a host identifier, a process or thread identifier of the process or thread invoking the function, and a nonrepeating value (sequence of bytes) for that process or thread.

Example

select SYS_GUID() from dual

  SYS_GUID()
= ================================
1 A20D42BA1F165DB5E04400144FB99F0A

SYS_GUID() as a default

Because SYS_GUID() “returns a globally unique identifier” we can use it as a default value in a Primary Key column of a table.

create table products(
    product_id raw(32) default sys_guid() not null primary key
    ............
);

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Unit Testing Validation in Annotation Based Validating Spring Beans

Friday, April 22nd, 2011

Motivation

I added validation, via annotations, to a Spring “Model” bean. I needed someway to Unit Test this validation, without running the container and without initialising the Spring context.

The bean (simplified)

package foo.bar;

import javax.validation.constraints.NotNull;
import javax.validation.constraints.Pattern;
import javax.validation.constraints.Size;

public final class ProductModel {

    @NotNull
    @Size(max=100)
    @Pattern(regexp="[^\n^\t^\r]+", message="Long Name must not contain New Lines, Carriage Returns or Tabs")
    private String longName;

    @Size(max=20)
    private String shortName;

    // rest snipped for brevity
}

The Unit Test

package foo.bar;

import java.util.Set;

import javax.validation.ConstraintViolation;

import junit.framework.Assert;

import org.hibernate.validator.HibernateValidator;
import org.junit.Before;
import org.junit.Test;
import org.springframework.validation.beanvalidation.LocalValidatorFactoryBean;

public class Temp {
    private LocalValidatorFactoryBean localValidatorFactory;

    @Before
    public void setup() {
        localValidatorFactory = new LocalValidatorFactoryBean();
        localValidatorFactory.setProviderClass(HibernateValidator.class);
        localValidatorFactory.afterPropertiesSet();
    }
    @Test
    public void testLongNameWithInvalidCharCausesValidationError() {
        final ProductModel productModel = new ProductModel();
        productModel.setLongName("A long name with\t a Tab character");
    	Set<ConstraintViolation<ProductModel>> constraintViolations = localValidatorFactory.validate(productModel);
    	Assert.assertTrue("Expected validation error not found", constraintViolations.size() == 1);
    }
}

More

It actually took me a few hours to work the above test out (simple as it is). If I hadn’t stumbled upon these Spring Unit Tests, I might never have got it.

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Posted in Spring | No Comments »

Spring MVC URI Template Example

Monday, April 18th, 2011

Background

So, I’m working on an existing Spring 3.x web project. This project heavily favours the use of annotations over XML configuration. As I was trawling through the source code I noticed “some wierd” syntax: “/{xxxx}” (which of course I had to look up!).

Most of the following is based upon the excellent Spring Documentation. I’ve lifted and rewritten the parts I require to serve as a condensed “aide-mémoire”.

Description

A URI Template is a URI-like string, containing one or more variable names. When you substitute values for these variables, the template becomes a URI.
(more...)

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Spring MVC 3 @ModelAttribute Annotation Example

Monday, April 18th, 2011

Background

So, I’m working on an existing Spring 3.x web project. This project heavily favours the use of annotations over XML configuration files. As I was trawling through the source code I noticed the “@ModelAttribute” annotation (which of course I had to look up!).

If the above background seems familiar that’s because it’s the same as for a previous Spring Annotation post I made (ed: this is in danger of turning into a mini-series)

Description

Most of the following is based upon the excellent Spring Documentation. I’ve simply lifted and rewritten the parts I require to serve as an “aide-mémoire”.

The @ModelAttribute annotation serves two purposes depending on how it is used:

(more...)

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Posted in Spring | 3 Comments »

Spring MVC 3.x @PathVariable Annotation Example

Friday, April 15th, 2011

Background

So, I’m working on an existing Spring 3.x web project. This project heavily favours the use of annotations over XML configuration files. As I was trawling through the source code I noticed the “@PathVariable” annotation (which of course I had to look up!).

Example

Imagine you’d like to create a controller that would allow users to see view products by using a URL such as http://foo.bar.com/productDetails/someProduct

e.g.

http://foo.bar.com/productDetails/widgetA - display details for widgetA
http://foo.bar.com/productDetails/widgetB - display details for widgetB

The @PathVariable annotation makes this easy…

package foo.bar;

import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;

@Controller
public class ShowProductController {

    @RequestMapping("/productDetails/{productName}") // Handle any request of the form "/productDetails/XXXXX"
    public String showProduct(Model model, @PathVariable("productName") String productName) {
        model.addAttribute("productName", productName);
        return "showProduct"; // viewname
    }
}

What just happened?

Note the {productName} in the @RequestMapping – this is the path variable. The @PathVariable annotation on the next line captures the value and binds it to the method argument

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Posted in Development, Examples | No Comments »