弹簧休息控制器具有生成的默认值的请求正文?

Question

我可以在我的休息控制器上请求有效负载，例如

{
"id" : "dffds-fsdf-dfdf-dsf",
"name" : "toto",
"age" : "18"
}

但正文参数 id 不是必需的，可能为空。在这种情况下，我需要生成一个 ID(使用 UUID 或其他任何东西)

有没有办法使用注释来做到这一点，例如？

Answer 1

一种方法是将默认值分配给变量，因此如果正文参数 id 为 null，则将分配此默认值，但如果在正文中传递 id，则不会分配此默认值。

public class Model {
private String name;
private String id=UUID.randomUUID().toString();
private int age;

}

Answer 2

我们必须至少解决两种情况：

1. id字段作为null发送，例如{ "id": null, ... }
2. 有效载荷中不存在id字段，例如{ "name" : "toto", "age" : "18" }

似乎没有可以产生这种行为的注释，但以下有效负载映射类应该可以解决问题：

import java.util.UUID;
public class Payload {
private String id = UUID.randomUUID().toString();
private String name;
private String age;
public String getId() {
return id;
}
public void setId(String id) {
this.id = id != null ? id : UUID.randomUUID().toString();
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getAge() {
return age;
}
public void setAge(String age) {
this.age = age;
}
/* You can safely remove this method, it's here only for test purposes. */
public static void main(String... args) throws java.io.IOException {
String[] tests = new String[] { 
"{ "id": "dffds-fsdf-dfdf-dsf", "name": "toto", "age": "18" }", 
"{ "name": "toto", "age": "18" }", 
"{ "age": "18" }", 
"{ "id": null, "name": "toto", "age": "18" }",
"{ "id": null, "age": "18" }", 
"{ "id": null, "name": "toto" }", 
"{ "id": null }", 
"{ }" 
};
for (String it : tests) {
Payload payload = new com.fasterxml.jackson.databind.ObjectMapper().readValue(it, Payload.class);
System.out.println(it + " => [id=" + payload.getId() + ", name=" + payload.getName() + ", age=" + payload.getAge() + "]");
}
}
}

如果运行main方法，将获得如下所示的输出，该输出应满足你的要求：

{ "id": "dffds-fsdf-dfdf-dsf", "name": "toto", "age": "18" } => [id=dffds-fsdf-dfdf-dsf, name=toto, age=18]
{ "name": "toto", "age": "18" } => [id=f3218a7c-6e2c-47fc-93b9-746ceec7b56b, name=toto, age=18]
{ "age": "18" } => [id=21899f52-d273-4c89-8a16-26871f4ec351, name=null, age=18]
{ "id": null, "name": "toto", "age": "18" } => [id=0a2ba8f6-cee3-44f0-89a6-e18ac55346d2, name=toto, age=18]
{ "id": null, "age": "18" } => [id=4f8125eb-ec68-4343-a04f-1490ffb81a76, name=null, age=18]
{ "id": null, "name": "toto" } => [id=b5d59feb-5730-4929-bc41-b0f17da68a39, name=toto, age=null]
{ "id": null } => [id=ccb9b192-daa3-4877-b232-56ec483b9d8e, name=null, age=null]
{ } => [id=d56cc66c-f9af-4dea-8ad4-86c16c9921a7, name=null, age=null]