@RequestParam vs @PathVariable

• @PathVariable is to obtain some placeholder from the URI (Spring call it an URI Template)— see Spring Reference Chapter 16.3.2.2 URI Template Patterns
• @RequestParam is to obtain a parameter from the URI as well — see Spring Reference Chapter 16.3.3.3 Binding request parameters to method parameters with @RequestParam

If the URL http://localhost:8080/MyApp/user/1234/invoices?date=12-05-2013 gets the invoices for user 1234 on December 5th, 2013, the controller method would look like:

@RequestMapping(value="/user/{userId}/invoices", method = RequestMethod.GET)public List<Invoice> listUsersInvoices(            @PathVariable("userId") int user,            @RequestParam(value = "date", required = false) Date dateOrNull) {  ...}

Also, request parameters can be optional, and as of Spring 4.3.3 path variables can be optional as well. Beware though, this might change the URL path hierarchy and introduce request mapping conflicts. For example, would /user/invoices provide the invoices for user null or details about a user with ID "invoices"?

@RequestParam annotation used for accessing the query parameter values from the request. Look at the following request URL:

http://localhost:8080/springmvc/hello/101?param1=10&param2=20

In the above URL request, the values for param1 and param2 can be accessed as below:

public String getDetails(    @RequestParam(value="param1", required=true) String param1,        @RequestParam(value="param2", required=false) String param2){...}

The following are the list of parameters supported by the @RequestParam annotation:

• defaultValue – This is the default value as a fallback mechanism if request is not having the value or it is empty.
• name – Name of the parameter to bind
• required – Whether the parameter is mandatory or not. If it is true, failing to send that parameter will fail.
• value – This is an alias for the name attribute

@PathVariable

@PathVariable identifies the pattern that is used in the URI for the incoming request. Let’s look at the below request URL:

http://localhost:8080/springmvc/hello/101?param1=10&param2=20

The above URL request can be written in your Spring MVC as below:

@RequestMapping("/hello/{id}")    public String getDetails(@PathVariable(value="id") String id,    @RequestParam(value="param1", required=true) String param1,    @RequestParam(value="param2", required=false) String param2){.......}

The @PathVariable annotation has only one attribute value for binding the request URI template. It is allowed to use the multiple @PathVariable annotation in the single method. But, ensure that no more than one method has the same pattern.

Also there is one more interesting annotation:@MatrixVariable

http://localhost:8080/spring_3_2/matrixvars/stocks;BT.A=276.70,+10.40,+3.91;AZN=236.00,+103.00,+3.29;SBRY=375.50,+7.60,+2.07

And the Controller method for it

 @RequestMapping(value = "/{stocks}", method = RequestMethod.GET)  public String showPortfolioValues(@MatrixVariable Map<String, List<String>> matrixVars, Model model) {    logger.info("Storing {} Values which are: {}", new Object[] { matrixVars.size(), matrixVars });    List<List<String>> outlist = map2List(matrixVars);    model.addAttribute("stocks", outlist);    return "stocks";  }

But you must enable:

<mvc:annotation-driven enableMatrixVariables="true" >

@RequestParam is use for query parameter(static values) like: http://localhost:8080/calculation/pow?base=2&ext=4

@PathVariable is use for dynamic values like : http://localhost:8080/calculation/sqrt/8

@RequestMapping(value="/pow", method=RequestMethod.GET)public int pow(@RequestParam(value="base") int base1, @RequestParam(value="ext") int ext1){    int pow = (int) Math.pow(base1, ext1);    return pow;}@RequestMapping("/sqrt/{num}")public double sqrt(@PathVariable(value="num") int num1){    double sqrtnum=Math.sqrt(num1);    return sqrtnum;}