Spring MVC

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One of the neat things you can do in Spring 3 MVC is to map request parameters into specific controller method input arguments. This is done by applying the <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">@RequestParam</tt> annotation to your controller method signature:<a href="https://www.blogger.com/null" name="more" style="background-color: white; color: #757575; font-family: 'Trebuchet MS', Trebuchet, sans-serif; font-size: 13px; line-height: 18.200000762939453px;"></a> 
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<code class="java">  @RequestMapping(value = "/help/detail", method = RequestMethod.GET)   public String displaySomeHelpDetail(@RequestParam("uuid") String uuid, Model model) {     return "view.name";   }</code></div>
 In the above example, the <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">@RequestMapping</tt> annotation routes all GET requests with the URL <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">/help/detail</tt> to your method. Using<tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">@RequestParam(“uuid”)</tt> means that Spring will then grab the <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">uuid</tt> value from the request string and attach it to the <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">String uuid</tt>method argument. Knowing this, you can see that the method above will process all GET requests with the following format:<tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">/help/detail?uuid=SomeValue</tt>, where <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">SomeValue</tt> becomes the <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">uuid</tt> argument. In the above, the <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">uuid</tt> is part of the <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">@RequestParam</tt>’s <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">value</tt> attribute and hence, the method signature could have been written as: 
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<code class="java">  @RequestMapping(value = "/help/detail", method = RequestMethod.GET)   public String displayMyFirstHelpDetail(@RequestParam(value="uuid") String uuid, Model model) {     return "view.name";   }</code></div>
 Indeed, <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">@RequestParam</tt> has two other optional attributes: <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">required</tt> and <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">defaultValue</tt>. <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">required</tt> is a boolean that’s applied to the <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">value</tt> attribute that defaults to <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">true</tt>. When true, then a exception is thrown if the request parameter is missing from the URL request string. When <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">required</tt> is <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">false</tt>, then an exception is not thrown and the input argument is set to <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">null</tt>. An example of how to use <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">required</tt> is: 
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<code class="java">  @RequestMapping(value = "/help/detail", method = RequestMethod.GET)   public String displaySomeOtherHelpDetail(@RequestParam(value="uuid", required=false) String uuid, Model model) {     return "view.name";   }</code></div>
 In the above code, a request URL string of <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">/help/detail?uuid=SomeValue</tt> will ensure that <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">uuid</tt> is set to <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">SomeValue</tt>. When the request param is missing and the URL request string is: <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">/help/detail</tt>, then the <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">uuid</tt> method argument will be set to <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">null</tt>. Using <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">defaultValue</tt> automatically sets <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">required</tt> to false, and inserts a ‘default value’ into your input argument when the request parameter is missing from your URL. An example of how to use <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">defaultValue</tt> is: 
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<code class="java">  @RequestMapping(value = "/help/detail", method = RequestMethod.GET)   public String displayYetOtherHelpDetail(@RequestParam(value="uuid", defaultValue="hello") String uuid, Model model) {     return "view.name";   } </code></div>
 In the above code, a request URL string of <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">/help/detail?uuid=SomeValue</tt> will ensure that <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">uuid</tt> is set to <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">SomeValue</tt>. When the request param is missing and the URL request string is: <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">/help/detail</tt>, then the <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">uuid</tt> method argument will be set to: <tt style="background-color: white; color: #757575; font-size: 13px; line-height: 18.200000762939453px;">hello</tt>. 
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Accessing Request Parameters using Spring 3 MVC

One of the neat things you can do in Spring 3 MVC is to map request parameters into specific controller method input arguments. This is don...

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