Spring 实战-第五章-构建Spring Web应用程序

SpringWeb应用程序，这里指的的是Spring MVC框架，包括了控制器，对象，视图解析，渲染等功能。



ref:http://blog.csdn.net/zuoluoboy/article/details/19766131　

MVC结构图如上，其中DispacherServlet是整个系统的核心，用于分配、调用各个模块。



流程上，请求到服务器，DispatcherServlet查询处理映射器（handler mapping)，确定需要使用哪个Controller，当Controller接收到请求后，会将数据打包和需要使用的视图名称，

返回到DispatcherServlet，DispatcherServlet会根据视图名称，找到对应的机图解析器（view resolver），视图解析器会根据数据和视图进行渲染，然后返回。

按照传统方式，需要增加很多xml配置，java based配置方式相对更简单明了。

配置DispatcherServlet

package spittr.config;

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
import spittr.web.WebConfig;

/**
* Created by jwlv on 2017/10/27.
*/
public class SpittrWebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

//for "root" application context (non-web infrastructure) configuration.
//返回的带有@Configuration注解的类将会用来配置ContextLoaderListener创建的应用上下文中的Bean
@Override
protected Class<?>[] getRootConfigClasses() {
return new Class<?>[]{RootConfig.class};
}

// for DispatcherServlet application context (Spring MVC infrastructure) configuration.
//返回的带有@Configuration注解的类将会用来定义DispatcherServlet应用上下文中的Bean
@Override
protected Class<?>[] getServletConfigClasses() {
return new Class<?>[]{WebConfig.class};
}

//将一个或多个路径映射到DispatcherServlet上
@Override
protected String[] getServletMappings() {
return new String[]{"/"};
}
}

当DispatcherServlet启动的时候，会创建Spring应用上下文，并加载配置文件或配置类中所声明的bean。

配置WebConfig

package spittr.web;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.servlet.ViewResolver;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

/**
* Created by jwlv on 2017/10/27.
*/
@Configuration
@EnableWebMvc
@ComponentScan("spittr.web")
public class WebConfig extends WebMvcConfigurerAdapter{

@Bean
public ViewResolver viewResolver(){
InternalResourceViewResolver resolver= new InternalResourceViewResolver();
resolver.setPrefix("/WEB-INF/views/");
resolver.setSuffix(".jsp");
resolver.setExposeContextBeansAsAttributes(true);
return resolver;
}

@Override
public void configureDefaultServletHandling(
DefaultServletHandlerConfigurer configurer){
configurer.enable();
}

//    @Autowired
//    private AnnotationConfigWebApplicationContext applicationContext;
}

@EnableWebMvc用来启用注解驱动的SpringMVC，如果是通过xml配置，需要xml中增加<mvc:annotation-driven>，这两个是等效的

于此同时，这还启用了其他特性，包括

Spring 3 style type conversion through a ConversionService instance in addition to the JavaBeans PropertyEditors used for Data Binding.

Support for formatting Number fields using the

@NumberFormat

annotation through the

ConversionService

.

Support for formatting Date, Calendar, Long, and Joda Time fields using the

@DateTimeFormat

annotation.

Support for validating @Controller inputs with

@Valid

, if a JSR-303 Provider is present on the classpath.

HttpMessageConverter support for

@RequestBody

method parameters and

@ResponseBody

method return values from

@RequestMapping

or

@ExceptionHandler

methods.

ref:https://docs.spring.io/spring/docs/3.2.x/spring-framework-reference/html/mvc.html#mvc-config-enable

viewResolver()方法会用来解析视图地址，根据controller返回的视图名称，和这里配置的前缀后缀，会找到对应的视图。

比如controller返回了“homepage”,根据这里的配置，找到的地址是~/WEB-INF/views/homepage.jsp。

定义控制器

package spittr.web;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

import static org.springframework.web.bind.annotation.RequestMethod.GET;

/**
* Created by jwlv on 2017/10/27.
*/
@Controller
@RequestMapping({"/home","/testhome"})
public class HomeController {
@RequestMapping(method=GET)
public  String home(){
return "home";
}

@RequestMapping(value="/homepage", method=GET)
public  String home2(){
return "home";
}

}

Controller的Mapping

handler mapping会根据请求的地址，结合controller上的RequestMapping，找到合适的controller，RequestMapping注解可以用于类和方法，可以灵活组合，method参数表示了请求的类型

如上controller，可以对应如下地址

类级别：http://localhost:8080/home,http://localhost:8080/testhome

方法级别：http://localhost:8080/homepage

类和方法组合：http://localhost:8080/home/homepage,http://localhost:8080/testhome/homepage

Controller的传值

请求传入到Controller，可以查询参数、路径参数、对象等方式实现

//通过查询参数传入
@RequestMapping(method=RequestMethod.GET)
public List<Spittle> spittles(
@RequestParam(value="max",defaultValue = "9999") long max,
@RequestParam(value="count",defaultValue = "20") int count) {
return spittleRepository.findSpittles(max,count);
}

//通过路径参数传入
@RequestMapping(value="/{spittleId}",method=RequestMethod.GET)
public String findOne(
@PathVariable("spittleId") long spittleId,
Model model){
model.addAttribute("spittle",spittleRepository.findOne(spittleId));
return "spittle";
}

//通过对象Post表单传入
@RequestMapping(value="/register",method = POST)
public String processRegistration(
@Valid Spitter spitter,
Errors errors){
if(errors.hasErrors()){
return "registerForm";
}
spitterRepository.save(spitter);
return "redirect:/spitter/"+ spitterRepository.findByUsername("").getUsername();
}

Controller传入到View，可以通过Model、Map、对象或集合，本质是传KeyValue

//调用addAttribute()方法并且不指定key的时候，key会根据值的对象类型判断,
//此处因为是一个List<Spittle>,故键将会推断为spittleList
@RequestMapping(method = RequestMethod.GET)
public String spittles(Model model){
model.addAttribute(
spittleRepository.findSpittles(Long.MAX_VALUE,20));
return "spittles";
}

//显示指定key
@RequestMapping(method = RequestMethod.GET)
public String spittles(Model model){
model.addAttribute("spittleList",
spittleRepository.findSpittles(Long.MAX_VALUE,20));
return "spittles";
}

//使用Map作为入参
@RequestMapping(method = RequestMethod.GET)
public String spittles(Map model) {
model.put("spittleList",
spittleRepository.findSpittles(Long.MAX_VALUE,20));
return "spittles";
}

//当处理器方法返回对象或集合时，这个值会放到模型中，模型的key会根据其类型推断得出。此处为spittleList
//逻辑视图的名称将会根据请求路径推断得出。因为这个方法处理针对“/spittles”的GET请求，
//因此视图的名称将会是spittles（去掉开头的斜线）
@RequestMapping(method = RequestMethod.GET)
public List<Spittle> spittles(Model model) {
return spittleRepository.findSpittles(Long.MAX_VALUE,20);
}

校验表单

Spring3.0开始，Spring MVC中提供了对Java校验API的支持（Java Validation API，又称JSR-303），当启用注解驱动时，不需要额外的配置，只要保证在类路径下包含这个API的实现即可，比如Hibernate Validator。

package spittr;

import org.apache.commons.lang3.builder.EqualsBuilder;
import javax.validation.constraints.NotNull;
import javax.validation.constraints.Size;

/**
* Created by jwlv on 2017/11/7.
*/
public class Spitter {
private Long id;

@NotNull
@Size(min = 5,max = 16)
private String username;

@NotNull
@Size(min = 5,max = 25)
private String password;

@NotNull
@Size(min = 2,max = 30)
private String firstName;

@NotNull
@Size(min = 2,max = 30)
private String lastName;

...
}

同时在Controller中使用@Valid注解，Errors对象要紧跟在有@Valid注解的参数后面，使用的时候，如果有不符合格式的传入，errors.hasErrors()会返回true。

@RequestMapping(value="/register",method = POST)
public String processRegistration(
@Valid Spitter spitter,
Errors errors){
if(errors.hasErrors()){
return "registerForm";
}
spitterRepository.save(spitter);
//return "redirect:/spitter/"+ spitter.getUsername();
return "redirect:/spitter/"+ spitterRepository.findByUsername("").getUsername();
}

code:https://github.com/ljw8947/SpringInAction/tree/master/Capter5/Spittr

参考：

https://docs.spring.io/spring/docs/3.2.x/spring-framework-reference/html/mvc.html

http://benweizhu.github.io/blog/2014/07/19/spring-validation-by-example/