@Detailed differences between pathvariable and @requestparam

Preface

Use springboot When the project is , I often see the mixing of these two annotations in projects
about springboot See my previous article for the basic knowledge points of ：
springboot From entry to mastery （ whole ）

Today, let's analyze in detail @pathvariable and @Requestparam（ All belong spring annotation ）

• @PathVariable：/manongyanjiuseng/18
• @RequestParam：/manongyanjiuseng?age=18

The difference is that one is to use ？, A use / To transmit data
This format is similar ：RESTFul From getting started to mastering super full parsing （ whole ）

1. The source code parsing

see @pathvariable Annotated source code ：

@Target({
    ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface PathVariable {
    
    @AliasFor("name")
    String value() default "";

    @AliasFor("value")
    String name() default "";

    boolean required() default true;
}

see @Requestparam Annotated source code ：

@Target({
    ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestParam {
    
    @AliasFor("name")
    String value() default "";

    @AliasFor("value")
    String name() default "";

    boolean required() default true;

    String defaultValue() default "\n\t\t\n\t\t\n\ue000\ue001\ue002\n\t\t\t\t\n";
}

Compare the source code of the two
@Requestparam Than @pathvariable One more parameter String defaultValue()
What do you mean ： If there is no corresponding parameter variable in the request body , Use default Assign a value to this parameter variable , Assign default values to

@pathvariable and @Requestparam These two annotations are generally linked with the following annotations ：
@GetMapping、@PostMapping and @RequestMapping Detailed difference with actual combat code （ whole ）

in general ：
@pathvariable receive url Parameters on the path
@RequestParam Receive parameter request params

Explain other parameters in the source code ：

• @Target Act on parameters
• @Retention The function is to define how long the annotation annotated by it will remain ,RetentionPolicy.RUNTIME Annotations are not only saved to class In file ,jvm load class After the document , There is still
• @Documented, Generate javadoc When you do, you will put @Documented The annotations are shown , But it's useless , Just a logo

2. Practical explanation

The above two annotations should match the parameters of the request body

@PathVariable annotation

@GetMapping ("/manongyanjiuseng/{age}")
@ResponseBody
public String xx( @PathVariable ( "age" ) String age) 

@Requestparam annotation

@RGetMapping ("/manongyanjiuseng")
@ResponseBody
public String xx( @RequestParam ( "age" ) String age)

The specific transmission parameters are as follows ：

• @PathVariable：/manongyanjiuseng/18
• @RequestParam：/manongyanjiuseng?age=18