SpringMVC 入门使用

@Target({ElementType.TYPE}) // 表明只能定义在类上面
@Retention(RetentionPolicy.RUNTIME) //保留策略是RUNTIME，在JVM加载类时，会把注解加载到JVM内存中（它是唯一可以用反射来读取注解的策略）
@Documented //@Documented用于描述其它类型的annotation应该被作为被标注的程序成员的公共API，因此可以被例如javadoc此类的工具文档化。Documented是一个标记注解，没有成员。
@Component //spring框架规定当一个类不好归类（service、dao、controller）的时候可以使用这个注解，由此可见即便好归类内部还是使用的@Component注解
public @interface Controller {
  /**
    * The value may indicate a suggestion for a logical component name,
    * to be turned into a Spring bean in case of an autodetected component.
    * @return the suggested component name, if any
    */
  String value() default "";
}

/**
* 1.@RequestMapping：除了修饰方法,还可以修饰类
* 2.类定义处：提供初步的请求信息映射.相对于WEB应用的根目录(窄化请求)
* 3.方法处：提供进一步的细分映射信息。相对于类定义处的URL。
*      若类定义处为标注@RequestMapping,则方法出的URL相对于WEB应用的根目录
*/
@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
@Mapping
public @interface RequestMapping {
  String[] value() default {};
  RequestMethod[] method() default {}; //限制请求方式
  String[] params() default {}; //要求请求的URL包含指定的参数
}

@Controller
@RequestMapping("/demo")
public class IndexController {
  @RequestMapping(value = "/test", method = RequestMethod.GET)
  public String index(Model model, HttpServletRequest request) {
    // 在游览器访问 http://localhost:8080/demo/test 将进入这里
    model.addAttribute("originURL", "");
    model.addAttribute("controllerName", "index");
    return "index";
  }
}

// http://localhost:8080/demo/sss
@RequestMapping(value = "/{slug:.+}", method = RequestMethod.GET)
public String index2(@PathVariable("slug") String slug, Model model) {
  LOG.info("DemoController index2 slug  " + slug);
  // common
  model.addAttribute("originURL", "demo/");
  model.addAttribute("controllerName", "demo");
  model.addAttribute("controllerMethod", "index2");
  model.addAttribute("slug", slug);
  return "demo";
}

//slug = sss

@Target(ElementType.PARAMETER)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestParam {
  String value() default "";//值即为请求参数的参数名
  boolean required() default true;//该参数是否是必须。默认值为true
  String defaultValue() default ValueConstants.DEFAULT_NONE;//请求参数的默认值
}

// http://localhost:8080/demo/para?slug=google
@RequestMapping(value = "/para", method = RequestMethod.GET)
public String index3(@RequestParam(value = "slug", defaultValue = "") String slug, Model model) {
  model.addAttribute("originURL", "demo/");
  model.addAttribute("controllerName", "demo");
  model.addAttribute("controllerMethod", "index3");
  model.addAttribute("slug", slug);
  return "demo";
}
slug = google

/**
 * Annotation that indicates a method return value should be bound to the web
 * response body. Supported for annotated handler methods in Servlet environments.
 *
 * 这个注解指明一个方法的返回值应该绑定在 web response body 中，在 Servlet 环境中支持注解处理方法
 *
 * <p>As of version 4.0 this annotation can also be added on the type level in
 * which case it is inherited and does not need to be added on the method level.
 */
@Target({ElementType.TYPE, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ResponseBody {
}

// http://localhost:8080/demo/json
@RequestMapping(value = "/json", method = RequestMethod.POST)
public @ResponseBody Domain index7(HttpServletRequest request, Model model) {
  LOG.info("DemoController demo index7");
  model.addAttribute("originURL", "demo/");
  model.addAttribute("controllerName", "demo");
  model.addAttribute("controllerMethod", "index7");

  Domain domain = new Domain();
  domain.setDomain("gggoogle.com");
  domain.setId(100);
  return domain;
}

/* response body
{
  "id": 100,
  "domain": "gggoogle.com"
}
*/

public class Address {
  private String city;
  ...
}

public class Persion {
  private String name;
  private Address address;
  ...
}

@RequestMapping(value = "/pojo", method = RequestMethod.POST)
public String index4(Persion persion, Model model) {
  `model.addAttribute("originURL", "demo/");
  model.addAttribute("controllerName", "demo");
  model.addAttribute("controllerMethod", "index4");
  model.addAttribute("persion", persion);
  return "demo";`
}

// http://localhost:8080/demo/req?slug=facebook
@RequestMapping(value = "/req", method = RequestMethod.GET)
public String index5(HttpServletRequest request, Model model) {
  String slug = request.getParameter("slug");
  model.addAttribute("originURL", "demo/");
  model.addAttribute("controllerName", "demo");
  model.addAttribute("controllerMethod", "index5");
  model.addAttribute("slug", slug);
  return "demo";
}