如何使用Spring Boot返回一组对象? [英] How to return a set of objects with Spring Boot?

问题描述

我做了关于Spring Boot的课程，它运行良好.但是，如果我想返回一组对象怎么办?我尝试做此但这是行不通的.我该怎么做呢?

I did a lesson about Spring Boot and it works perfectly. But what if I want to return a set of objects ? I tried doing this but it doesn't work. How can I do it correctly ?

具有一个对象(有效):

With one object (it works):

@RequestMapping("/greeting")
public Greeting greeting(@RequestParam(value="name", defaultValue = "World") String name) {
    return new Greeting(counter.incrementAndGet(),
            String.format(template, name));
}

有很多对象(无效):

With many objects (it doesn't work):

@RequestMapping(value = "/greeting", method = RequestMethod.GET, consumes = MediaType.APPLICATION_JSON_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
public @ResponseBody List<Greeting> greeting() {
    Greeting greeting1 = new Greeting(1, "One");
    Greeting greeting2 = new Greeting(2, "Two");
    List<Greeting> list = new ArrayList<>();
    list.add(greeting1);
    list.add(greeting2);
    return list;
}

推荐答案

如果将原始方法与新方法(使用List)进行比较，则会发现一些区别.

If you compare your original method to your newly made one (with a List), you'll notice a few differences.

首先，在@RequestMapping批注中，您现在正在使用属性consumes和produces. produces在这里不是问题，因为您生成的响应应该是JSON. 但是，您什么都没消费，因此您应该放弃consumes.

First of all, within the @RequestMapping annotation you're now using the properties consumes and produces. produces is not a problem here, because you are producing a response that should be JSON. However you're not consuming anything, so you should leave away the consumes.

@RequestMapping(value = "/greeting", method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
public @ResponseBody
List<Greeting> greeting() {
    Greeting greeting1 = new Greeting(1, "One");
    Greeting greeting2 = new Greeting(2, "Two");
    List<Greeting> list = new ArrayList<>();
    list.add(greeting1);
    list.add(greeting2);
    return list;
}

作为旁注，您可能还会注意到您使用了@ResponseBody批注.将其放在此处不会引起任何错误，但不是必须的，因为如果您正确地遵循了Spring教程，则应该使用@RestController注释控制器，并已这样做，您已经告诉Spring它将使用响应身体.

As a sidenote, you might also notice that you used the @ResponseBody annotation. Putting it here won't cause any errors, but it is not necessary, because if you followed the Spring tutorial correctly, you should have annotated your controller with @RestController and by doing that, you already tell Spring that it will use a response body.

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