【Java】SpringMVC参数接收（一）

1、接收单个参数

（1）直接接收参数

@RequestMapping("/hello")
@RestController
public class HelloSpring {@RequestMapping("/t2")public String t2(String name){return "name=" + name;}
}

 当没有传入参数时，返回null

（2）包装类接收

如果我们换成int，再次看看结果

@RequestMapping("/hello")
@RestController
public class HelloSpring {@RequestMapping("/t2")public String t2(String name){return "name=" + name;}
}

postman报错。报错提示我们应该使用包装类

@RequestMapping("/hello")
@RestController
public class HelloSpring {@RequestMapping("t4")public String t4(Integer age){return "age=" + age;}
}

不传参数时，返回null，不再报错 

SpringMVC接收参数时最好使用包装类

 2、多个参数

（1）直接写 

@RequestMapping("/hello")
@RestController
public class HelloSpring {@RequestMapping("t5")public String t5(String name,Integer age){return "name=" + name + ", " + "age=" + age;}
}

（2）使用类包装

UserInfo类

public class UserInfo {private String name;private int age;private int id;public String getName() {return name;}public void setName(String name) {this.name = name;}public int getAge() {return age;}public void setAge(int age) {this.age = age;}public int getId() {return id;}public void setId(int id) {this.id = id;}@Overridepublic String toString() {return "UserInfo{" +"name='" + name + '\'' +", age=" + age +", id=" + id +'}';}
}

@RequestMapping("/hello")
@RestController
public class HelloSpring {@RequestMapping("t6")public String t6(UserInfo userInfo){return userInfo.toString();}
}

3、修改参数名 

后端接收参数的名字是跟前端保持一致的，因此我们要使用其他参数名时，则要对其进行修改

@RequestMapping("/hello")
@RestController
public class HelloSpring {@RequestMapping("t7")public String t7(@RequestParam("name")String username){return "name=" + username;}
}
//@RequestParam()中所写的是本来的参数名
//String后写的是修改后的参数名

但是如果不传入参数，就会报错

可见，上述修改参数是强制传入参数。为了能不报错，我们使参数required为false

@RequestMapping("/hello")
@RestController
public class HelloSpring {@RequestMapping("t7")public String t7(@RequestParam(value = "name",required = false)String username){return "name=" + username;}
}

这样就算不传入参数，也不会报错

4、接收数组参数

（1）直接传数组 

@RequestMapping("/hello")
@RestController
public class HelloSpring {@RequestMapping("t8")public String t8(String[] arr){return Arrays.toString(arr);}
}

（2）传集合

@RequestMapping("/hello")
@RestController
public class HelloSpring {@RequestMapping("t9")public String t9(@RequestParam(value = "list",required = false)List<String> list){return list.toString();}
}