文章目录

• 一、SpringMVC常用注解
• • 1.1 @PathVariable
  • 1.2 @RequestParam
  • 1.3 @CookieValue
  • 1.4 @RequestHeader
  • 1.5 @SessionAttribute
  • 1.6 @SessionAttributes
  • 1.7 @RequestAttribute
  • 1.8 @ModelAttribute

一、SpringMVC常用注解

搭建项目，引入Maven依赖：

org.springframeworkspring-webmvc5.2.9.RELEASEorg.apache.tomcattomcat-api8.5.41org.projectlomboklombok1.18.18

• 实体类：

package com.dfbz.entity;import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;/*** @author lscl* @version 1.0* @intro:*/
@Data
@AllArgsConstructor
@NoArgsConstructor
public class City {private Integer id;         // 城市idprivate String cityName;    // 城市名称private Double GDP;         // 城市GDP,单位亿元private Boolean capital;    // 是否省会城市
}

• web.xml：

characterEncodingFilterorg.springframework.web.filter.CharacterEncodingFiltercharacterEncodingFilter/*dispatcherorg.springframework.web.servlet.DispatcherServletcontextConfigLocationclasspath:springmvc.xmldispatcher/

• springmvc.xml：

1.1 @PathVariable

作用：用于接收Rest风格请求的路径参数；将方法形参和url 的占位符进行绑定；

• 源码：

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

• name/value：当url中的占位符和方法形参名称不一致时，可以使用name/value属性进行绑定；
• required：是否必须提供占位符，默认为true；

• 测试：

package com.dfbz.controller;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/*** @author lscl* @version 1.0* @intro: @PathVariable注解*/
@Controller
@RequestMapping("/demo01")
public class Demo01Controller_PathVariable {@GetMapping("/{id}/{name}")public void test(@PathVariable Integer id,@PathVariable(value = "name") String cityName,                  // 把url上的name值赋值给cityNameHttpServletResponse response) throws IOException {response.setContentType("text/html;charset=utf8");response.getWriter().write("id: "+id+"
");response.getWriter().write("cityName: "+cityName+"
");}@GetMapping("/{id}")public void test2(@PathVariable Integer id,@PathVariable(value = "aaa",required = false) String cityName,                  // 没有aaa占位符也没关系HttpServletResponse response) throws IOException {response.setContentType("text/html;charset=utf8");response.getWriter().write("id: "+id+"
");response.getWriter().write("cityName: "+cityName+"
");}}

1.2 @RequestParam

作用：接收前端提交的参数（POST/GET提价都可以接收）；当接收的参数的变量名与表单的name属性不一样时可以使用@RequestParam来绑定，同时可以封装其他类型的对象，如List、Set、Map

• 源码：

@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";
}

• name/value：当前端传递的参数名称和方法形参名称不一致时，可以使用name/value属性进行绑定；
• required：是否必须提供传递此参数，默认为true；
• defaultValue：如果前端没有传递此参数，默认为defaultValue的值；

• 测试：

package com.dfbz.controller;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;
import java.util.Map;/*** @author lscl* @version 1.0* @intro: @RequestParam注解*/
@Controller
@RequestMapping("/demo02")
public class Demo02Controller_RequestParam {@GetMapping("/demo01")public void demo01(Integer id,@RequestParam("name") String cityName,                  // 将前端传递的name参数与cityName进行绑定(name参数必须传递)HttpServletResponse response) throws IOException {response.setContentType("text/html;charset=utf8");response.getWriter().write("id: " + id + "
");response.getWriter().write("cityName: " + cityName + "
");}@GetMapping("/demo02")public void demo02(@RequestParam(required = false) Integer id,                       // id可以不传递@RequestParam(defaultValue = "guangzhou") String cityName,        // cityName参数如果没有传递默认为guangzhouHttpServletResponse response) throws IOException {response.setContentType("text/html;charset=utf8");response.getWriter().write("id: " + id + "
");response.getWriter().write("cityName: " + cityName + "
");}/*** map类型* @param maps* @param response* @throws IOException*/@GetMapping("/demo03")public void demo03(@RequestParam Map maps,HttpServletResponse response) throws IOException {response.setContentType("text/html;charset=utf8");response.getWriter().write("id: " + maps.get("id") + "
");response.getWriter().write("cityName: " + maps.get("cityName") + "
");}/*** List类型* @param ids* @param response* @throws IOException*/@PostMapping("/demo04")public void demo04(@RequestParam("ids") List ids,HttpServletResponse response) throws IOException {response.setContentType("text/html;charset=utf8");response.getWriter().write("id: " + ids.toString() + "
");}
}

1.3 @CookieValue

作用：获取Cookie中的数据

• 源码：

@Target({ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface CookieValue {@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";
}

• name/value：Cookie中的参数名称和方法形参名称不一致时，可以使用name/value属性进行绑定；
• required：是否必须提供此参数Cookie参数，默认为true；
• defaultValue：如果Cookie中没有此参数，默认为defaultValue的值；

• 测试：

package com.dfbz.controller;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.CookieValue;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/*** @author lscl* @version 1.0* @intro: @CookieValue*/
@Controller
@RequestMapping("/demo03")
public class Demo03Controller_CookieValue {@GetMapping("/demo01")public void demo01(@CookieValue String JSESSIONID,HttpServletResponse response) throws IOException {response.setContentType("text/html;charset=utf8");response.getWriter().write("JSESSIONID: " + JSESSIONID + "
");}
}

1.4 @RequestHeader

作用：获取请求头中的数据

• 源码：

@Target({ElementType.PARAMETER})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface RequestHeader {@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";
}

• 测试代码：

package com.dfbz.controller;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/*** @author lscl* @version 1.0* @intro: @RequestHeader*/
@Controller
@RequestMapping("/demo04")
public class Demo04Controller_RequestHeader {@GetMapping("/demo01")public void demo01(@RequestHeader String Host,HttpServletResponse response) throws IOException {response.setContentType("text/html;charset=utf8");response.getWriter().write("Host: " + Host + "
");}
}

1.5 @SessionAttribute

作用：从session中获取一个值封装到参数中

• 源码：

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

• 测试代码：

package com.dfbz.controller;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.SessionAttribute;import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;/*** @author lscl* @version 1.0* @intro: @SessionAttribute*/
@Controller
@RequestMapping("/demo05")
public class Demo05Controller_SessionAttribute {@GetMapping("/demo01")public String demo01(HttpSession session) throws IOException {session.setAttribute("loginUser", "zhangsan");return "/demo05/demo02";}/*** 从session中取出loginUser(必须要有这个属性)* @param loginUser* @param response* @throws IOException*/@GetMapping("/demo02")public void demo02(@SessionAttribute String loginUser,HttpServletResponse response) throws IOException {response.setContentType("text/html;charset=utf8");response.getWriter().write("loginUser: " + loginUser + "
");}
}

1.6 @SessionAttributes

作用：把BindingAwareModelMap中的指定的key或者指定的属性的值也存入一份进session域

tips：@SessionAttributes注解并不能把存入request域的值也存入session中

• 源码：

@Target({ElementType.TYPE})		// 标注在类上的
@Retention(RetentionPolicy.RUNTIME)
@Inherited
@Documented
public @interface SessionAttributes {@AliasFor("names")String[] value() default {};@AliasFor("value")String[] names() default {};Class[] types() default {};
}

• 测试代码：

package com.dfbz.controller;import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.SessionAttributes;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.Map;/*** @author lscl* @version 1.0* @intro: @SessionAttributes*/// 把BindingAwareModelMap中的username属性和所有的Integer类型的属性都存入一份在session中
@SessionAttributes(value = {"username"}, types = {Integer.class})
@Controller
@RequestMapping("/demo06")
public class Demo06Controller_SessionAttributes {@GetMapping("/demo01")public String demo01(Map map, HttpServletRequest request) throws IOException {map.put("username", "admin");map.put("password", "123");map.put("age", 23);map.put("tall", 1.78);// 存入request域的值不能被存入sessionrequest.setAttribute("test",111);return "/demo06/demo02";}@GetMapping("/demo02")public void demo02(HttpSession session, HttpServletResponse response) throws IOException {response.setContentType("text/html;charset=utf8");response.getWriter().write("username: " + session.getAttribute("username") + "
");response.getWriter().write("password: " + session.getAttribute("password") + "
");response.getWriter().write("age: " + session.getAttribute("age") + "
");response.getWriter().write("tall: " + session.getAttribute("tall") + "
");response.getWriter().write("test: " + session.getAttribute("test") + "
");}
}

1.7 @RequestAttribute

作用：获取request域中的数据；

测试代码：

package com.dfbz.controller;import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestAttribute;
import org.springframework.web.bind.annotation.RequestMapping;import javax.servlet.http.HttpServletResponse;
import java.io.IOException;/*** @author lscl* @version 1.0* @intro:*/
@Controller
@RequestMapping("/demo07")
public class Demo07Controller_RequestAttribute {@GetMapping("/demo01")public String demo01(Model model) throws IOException {// 在请求域中添加几个属性model.addAttribute("username", "zhangsan");model.addAttribute("password", "123");return "/demo07/demo02";}@GetMapping("/demo02")public void demo02(@RequestAttribute("username") String name,      // 获取请求域中的username属性值@RequestAttribute String password,              // 获取请求域中password属性值HttpServletResponse response) throws IOException {response.getWriter().println("username: "+name);response.getWriter().println("password: "+password);}
}

1.8 @ModelAttribute

作用：@ModelAttribute注解可以作用于方法和参数上

• 作用于方法上：在执行Controller其他所有方法之前执行@ModelAttribute注解标注的方法

• 作用于参数上：获取ModelAttribute标注的方法中BingMap中的某个值到某个属性到形参上，并且此次的BingMap会传递到下一个handler方法；BingMap中的值以前端传递的为准，如果前端传递了参数则以前端为准，如果没有传递参数则保持@ModelAttribute标注方法中的默认值；

• 源码：

@Target({ElementType.PARAMETER, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ModelAttribute {@AliasFor("name")String value() default "";@AliasFor("value")String name() default "";boolean binding() default true;
}

• 测试代码：

package com.dfbz.controller;import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.Map;/*** @author lscl* @version 1.0* @intro: @ModelAttribute注解作用与方法上*/
@Controller
@RequestMapping("/demo08")
public class Demo08Controller_ModelAttribute {@ModelAttributepublic void model(Model model, ModelMap modelMap, Map map) {model.addAttribute("username", "zhangsan");modelMap.addAttribute("password", "admin");map.put("email","zhangsan@qq.com");}@RequestMapping("/demo01")public void demo01(@ModelAttribute("username") String username,            // 注意: 形参名和BindingMap中的key一样也要写@ModelAttribute("password") String password,@ModelAttribute("email") String email,HttpServletResponse response) throws Exception {response.getWriter().println("username: " + username);response.getWriter().println("password: " + password);response.getWriter().println("email: " + email);}
}

Tips：@ModelAttribute只能获取BingMap中的数据，不能获取request中的数据；

应用场景：现在需要修改一个City信息，有某些应用信息前端不提交（默认为null），

• 表单：

<%@ page contentType="text/html;charset=UTF-8" language="java" %>




城市ID：城市名称：GDP：是否省会：

• Controller：

package com.dfbz.controller;import com.dfbz.entity.City;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.RequestMapping;import java.io.IOException;
import java.util.Map;/*** @author lscl* @version 1.0* @intro: @ModelAttribute注解作用与方法上*/
@Controller
@RequestMapping("/demo09")
public class Demo09Controller_ModelAttribute02 {/*** ModelAttribute标注的方法在所有的handler方法之前执行** @param maps* @throws IOException*/@ModelAttributepublic void model(Map maps) throws IOException {maps.put("city", new City(1, "南宁", 4700.00, true));System.out.println("model方法执行了...");}@RequestMapping("/demo01")public void demo01(@ModelAttribute("city") City city, HttpServletResponse response) throws Exception{        // 如果前端没有传递则以@ModelAttribute标注的为准,如果传递了则以前端参数为准response.setContentType("text/html;charset=utf8");response.getWriter().println(city);}
}