What are the methods for obtaining parameters in Springboot EL?

Springboot EL method of obtaining parameters: 1. Use @RequestParam annotation; 2. Use EL expression to obtain request parameters; 3. Use model attributes. Detailed introduction: 1. Use the @RequestParam annotation. The @RequestParam annotation can be used to bind request parameters to the parameters of the controller method; 2. Use EL expressions to obtain the request parameters. If you do not use the @RequestParam annotation, or you want to dynamically To obtain request parameters, you can use EL expression and so on.

The operating system for this tutorial: Windows 10 system, DELL G3 computer.

Spring Boot is a fast and simple framework for creating Spring applications. In Spring Boot, you can use Expression Language (EL) to get request parameters. EL is a powerful tool in Spring MVC that allows you to access request parameters directly in controller methods. The following are several ways to use EL to obtain request parameters:

1. Use the @RequestParam annotation

@RequestParam annotation can be used to bind request parameters to the controller on the method parameters. For example, assuming you have a request parameter called search, you can bind it to a parameter in a controller method using:

@RequestMapping("/search")  
public String search(@RequestParam("search") String query) {  
    // 处理查询  
    return "searchResult";  
}

In this example, @RequestParam("search") tells Spring MVC binds the value of the request parameter named search to the query parameter.

2. Use EL expressions to obtain request parameters

If you do not use the @RequestParam annotation, or want to obtain request parameters dynamically, you can use EL expressions to access request parameters. For example, if you have a request parameter named id, you can use the following EL expression to get its value:

@RequestMapping("/details/{id}")  
public String details(@PathVariable Long id, Model model) {  
    // 处理详情请求  
    model.addAttribute("id", id);  
    return "details";  
}

In this example, {id} is a path variable, which will be replaced is the actual request parameter value. You can then use the EL expression ${id} to access the value of that path variable. Note that this expression is used in the JSP page, not in the controller method.

3. Use model attributes

If you want to add request parameters to the model for use in JSP pages, you can use the following method:

@RequestMapping("/profile")  
public String profile(Model model) {  
    String username = request.getParameter("username");  
    model.addAttribute("username", username);  
    return "profile";  
}

In this example, we first use the request.getParameter("username") method to get the value of the request parameter named username. We then add that value to the model using the model.addAttribute("username", username) method. Finally, we return a view called profile that has access to a model property called username. Note that the request object in this example is obtained from the Spring MVC context. If you want to use EL expressions to access model properties in a controller method, you need to use the Model object instead of the request object directly. For example, you can use the following EL expression to access a model property named username: ${username}.

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