3.5 Spring MVC参数传递

Spring MVC的Controller接收请求参数的方式有多种，本节主要介绍Spring MVC下的HttpServletRequest、基本数据类型、Java Bean、数组、List、Map、JSON参数传递方式，同时解决POST请求中文乱码问题。

1. HttpServletRequest参数传递

@Controller
@RequestMapping("/param")
public class ParamController {/***  通过HttpServletRequest接收参数*/@RequestMapping("/servlet")public void servlet(HttpServletRequest request, HttpServletResponse response) throws IOException {String name = request.getParameter("name");System.out.println("name=" + name);PrintWriter writer = response.getWriter();writer.print("hello " + name);writer.flush();writer.close();}
}

2. 基本数据类型参数传递

基本数据类型以及他们的包装类。

@Controller
@RequestMapping("/param")
public class ParamController {/*** 使用基本数据类型和String类型*/@RequestMapping("/simple")@ResponseBodypublic String simple(int id, String name) throws IOException {String str = "id = " + id + ",name = " + name;System.out.println(str);return str;}
}

3. Java Bean参数传递

@Controller
@RequestMapping("/param")
public class ParamController {/*** JavaBean传递参数*/@RequestMapping(value = "/bean",produces = "text/plain;charset=UTF-8",method = RequestMethod.POST)@ResponseBodypublic String paramBean(Student student){System.out.println(student);return student.toString();}
}

4. 数组参数传递

@Controller
@RequestMapping("/param")
public class ParamController {/*** 数组参数*/
@RequestMapping(value = "/array",method = RequestMethod.POST)
@ResponseBody
public String array(String[] hobbies){for(String hobby : hobbies){System.out.println(hobby);}return "success";
}
}

5. List参数传递

@Controller
@RequestMapping("/param")
public class ParamController {/*** List参数*/
@RequestMapping(value = "/list",method = RequestMethod.POST)
@ResponseBody
public String list(@RequestParam List<String> hobbyList){hobbyList.forEach(hobby -> System.out.println(hobby));return "success";
}
}

6. Map参数传递

@Controller
@RequestMapping("/param")
public class ParamController {/*** Map参数*/
@RequestMapping(value = "/map",method = RequestMethod.POST)
@ResponseBody
public String map(@RequestParam Map<String,Object> map){System.out.println(map);return "success";
}
}

7. JSON参数传递

JSON格式采用键值对的方式来表示数据，由花括号 {} 包含对象，由方括号 [] 包含数组，可通过JSON在线解析工具进行校验/格式化，具体格式如下：

对象

对象是一个无序的键/值对集合，每个键后面需要添加一个冒号（:），键/值对之间使用逗号（，）分隔。

{"id": "1","name": "zhangsan","age":20
}

数组

数组可以包含多个元素，每个元素之间使用逗号（，）分隔，可以包含简单值、对象或者其他数组。

[{"id": "1","name": "zhangsan"},{"id": "2","name": "zhangsan"}
]

Spring MVC可以使用Jackson框架作为JSON的转换器。

通过@RequestBody可以将前端的JSON参数转成Java Bean、Map、List等引用类型。

通过@ResponseBody可以将后端的Java Bean、Map、List等引用类型转成JSON结果输出。

使用Jackson时需要三个jar包jackson-databind.jar、jackson-core.jar、jackson-annotations.jar。如果Spring MVC创建的是Maven项目，仅需要依赖jackson-databind，因为它传递依赖了jackson-core和jackson-annotations。

@Controller
@RequestMapping("/json")
public class JsonController {/*** json bean*/@RequestMapping(value = "/bean",method = RequestMethod.POST)@ResponseBodypublic Object bean(@RequestBody Student student){System.out.println(student);Map<String,Object> map = new HashMap<String,Object>();map.put("code",200);map.put("msg","success");map.put("data",student.toString());return map;}/*** json map*/@RequestMapping(value = "/map",method = RequestMethod.POST)@ResponseBodypublic Object map(@RequestBody Map<String,Object> jsonMap){System.out.println(jsonMap);Map<String,Object> map = new HashMap<String,Object>();map.put("code",200);map.put("msg","success");map.put("data",jsonMap);return map;}/*** json list*/@RequestMapping("/list")@ResponseBodypublic Object list(@RequestBody List<Student> studentList){System.out.println(studentList);Map<String,Object> map = new HashMap<String,Object>();map.put("code",200);map.put("msg","success");map.put("data",studentList);return map;}
}

8. Spring MVC解决POST请求中文乱码问题

Spring提供了CharacterEncodingFilter解决POST请求中的中文乱码问题，在web.xml中配置CharacterEncodingFilter。

<web-app><!--解决POST中文乱码问题 过滤器--><filter><filter-name>encodingFilter</filter-name><filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class><init-param><param-name>encoding</param-name><param-value>utf-8</param-value></init-param></filter><filter-mapping><filter-name>encodingFilter</filter-name><url-pattern>/*</url-pattern></filter-mapping>
</web-app>