Springboot (b) handlermethodargumentresolver

As follows: During the development process, you may use Requestparam annotations, set required = True, tell the front-end that this parameter is mandatory,
But the basic understanding used, usually because the front-end passed an empty string, resulting in a validation pass, poor practicality,
Native annotations are basically not enough to meet actual development needs, so you need to write one yourself.

@ResponseBody @requestmapping ("/data")  Public map<string, object> data (        true) String b) {    returnnew Hashmap<>();}

Handlermethodargumentresolver

At this point you need to write a section, Handlermethodargumentresolver, literal translation is, the decomposition of the function parameters, the implementation of this interface is also very simple,

Supportsparameter (Support parameters): You can set some flags, indicating that you can handle these parameters, return ture to execute the resolveargument () function
Resolveargument (Decomposition arguments): The specific method of handling the arguments

ImportOrg.springframework.core.MethodParameter;Importorg.springframework.web.bind.support.WebDataBinderFactory;Importorg.springframework.web.context.request.NativeWebRequest;ImportOrg.springframework.web.method.support.HandlerMethodArgumentResolver;ImportOrg.springframework.web.method.support.ModelAndViewContainer;/*** Created by 12614 on 2018/5/11.*/ Public classTestargumentresolverImplementsHandlermethodargumentresolver {@Override Public BooleanSupportsparameter (Methodparameter methodparameter) {return true; } @Override PublicObject resolveargument (methodparameter methodparameter, Modelandviewcontainer Modela Ndviewcontainer, Nativewebrequest nativewebrequest, WebD Atabinderfactory webdatabinderfactory)throwsException {System.out.println ("Testargumentresolver:resolveargument"); return NULL; }}

Spring Configuration

< Mvc:annotation-driven >      < mvc:argument-resolvers >        <  class= "xxxxx Full class name"/>      </MVC: Argument-resolvers></mvc:annotation-driven>

Springboot Configuration

Since the 0 configuration, do not violate the original design deliberately to enable the XML configuration, add Handlermethodargumentresolver in the Webmvcconfigureradapter is good ,

Importorg.springframework.context.annotation.Configuration;ImportOrg.springframework.web.method.support.HandlerMethodArgumentResolver;ImportOrg.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;Importjava.util.List;/*** Created by 12614 on 2018/5/11.*/@Configuration Public classApplicationconfigurerextendsWebmvcconfigureradapter {@Override Public voidAddargumentresolvers (listargumentresolvers) {        Super. Addargumentresolvers (argumentresolvers); Argumentresolvers.add (Newtestargumentresolver ()); }}

Simple Case-Custom annotations

Importjava.lang.annotation.*;/*** Created by 12614 on 2018/5/11.*/@Documented @target (elementtype.parameter) @Retention (retentionpolicy.runtime) Public@InterfaceParams {@AliasFor ("Name") String value ()default""; @AliasFor ("Value") String name ()default""; BooleanRequired ()default true; BooleanNotempty ()default true; intMaxLength ()defaultInteger.max_value; String DefaultValue ()default"\n\t\t\n\t\t\n\ue000\ue001\ue002\n\t\t\t\t\n";}

Parametric decomposition device

ImportOrg.springframework.core.MethodParameter;Importorg.springframework.web.bind.support.WebDataBinderFactory;Importorg.springframework.web.context.request.NativeWebRequest;ImportOrg.springframework.web.method.support.HandlerMethodArgumentResolver;ImportOrg.springframework.web.method.support.ModelAndViewContainer;Importjavax.servlet.http.HttpServletRequest;/*** Created by 12614 on 2018/5/11.*/ Public classTestargumentresolverImplementsHandlermethodargumentresolver {@Override Public BooleanSupportsparameter (Methodparameter methodparameter) {//If the function contains our custom annotations, go to the resolveargument () function        returnMethodparameter.hasparameterannotation (Params.class); } @Override PublicObject resolveargument (methodparameter methodparameter, Modelandviewcontainer Modela Ndviewcontainer, Nativewebrequest nativewebrequest, WebD Atabinderfactory webdatabinderfactory)throwsException {System.out.println ("Testargumentresolver:resolveargument"); params params= Methodparameter.getparameterannotation (Params.class); String paramname=Params.name (); if(ParamName = =NULL) {paramname=Methodparameter.getparametername (); }        //Simple case: If the client does not pass the value, set the default valueObject res = nativewebrequest.getnativerequest (httpservletrequest.class). GetParameter (paramname); returnres = =NULL?params.defaultvalue (): res; }}

Usage Scenarios

    @ResponseBody    @RequestMapping ("/data")    public map<string, object> data (            true, maxLength = DefaultValue = "AAA") String a) {        System.out.println (a);         returnnull;    }

Springboot (b) handlermethodargumentresolver