Interceptors
Interceptor和Filter的功能一样，都是用于拦截incoming HTTP requests。但是Filter要比interceptor更强大些，因为Filter能够修改incoming request/response。
Interceptor的回调接口
- preHandler： Called before the handler is invoked
- postHandler: 在Handler调用之后，View渲染之前调用。可以用于替换model里的共享对象
- afterCompletion：在request处理完成之后。该方法无论preHandler方法调用成功与否都会被调用。可以用于清除一些资源。
Interceptor接口
- org.springframework.web.servlet.HandlerInterceptor
- org.springframework.web.context.request.WebRequestInterceptor
这两个Interceptor的最大区别在与WebRequestInterceptor跟底层技术独立，可以用于JSF或者Servlet，而HandlerIntercepotr只能用于Servlet。HandlerInterceptor的preHandler方法返回false可以用于阻止handler的调用。
Configuring
配置Interceptor分为两步：
* 配置Interceptor
* 关联Interceptor和Handler：有两个方法来完成关联：
1. 显示的把interceptors添加到handler mapping的配置里去
2. 使用org.springframework.web.servlet .config.annotation.InterceptorRegistry添加（推荐这种方式）
显示关联HandlerMapping和Interceptor
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| package com.apress.prospringmvc.bookstore.web.config;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurationSupport;
import org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping;
@Configuration
@EnableWebMvc
@ComponentScan(basePackages = { "com.apress.prospringmvc.bookstore.web" })
public class WebMvcContextConfiguration extends WebMvcConfigurationSupport {
@Override
public RequestMappingHandlerMapping requestMappingHandlerMapping() {
RequestMappingHandlerMapping handlerMapping;
handlerMapping = super.requestMappingHandlerMapping();
handlerMapping.setInterceptors(getAllInterceptors());
return handlerMapping
}
}
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使用InterceptorRegistry关联HandlerMapping和Interceptor
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| package com.apress.prospringmvc.bookstore.web.config;
//Other imports omitted
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
@Configuration
@EnableWebMvc
@ComponentScan(basePackages = { "com.apress.prospringmvc.bookstore.web" })
public class WebMvcContextConfiguration extends WebMvcConfigurerAdapter {
@Override
public void addInterceptors(InterceptorRegistry registry) {
registry.addInterceptor(localeChangeInterceptor());
}
@Bean
public HandlerInterceptor localeChangeInterceptor() {
LocaleChangeInterceptor localeChangeInterceptor;
localeChangeInterceptor = new LocaleChangeInterceptor();
localeChangeInterceptor.setParamName("lang");
return localeChangeInterceptor;
}
//... Other methods omitted
}
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Limiting an Interceptor to Certain URLs
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| package com.apress.prospringmvc.bookstore.web.config;
//Imports omitted
@Configuration
@EnableWebMvc
@ComponentScan(basePackages = { "com.apress.prospringmvc.bookstore.web" })
public class WebMvcContextConfiguration extends WebMvcConfigurerAdapter {
@Override
public void addInterceptors(InterceptorRegistry registry) {
InterceptorRegistration registration;
registration = registry.addInterceptor(localeChangeInterceptor());
registation.addPathPatterns("/customers/**");
}
//Other methods omitted
}
|