Spring POST接收具有空值的对象 [英] Spring POST receives object with null values

问题描述

我有一个AngularJS Web应用程序，看起来它正在正确地将JSON发送到Tomcat服务器，但是服务器接收到空值. 这个问题没有帮助，因为我的属性名称已经是小写，并且这个问题没有帮助，因为我已经有了@RequestBody表示法. 正如评论中指出的那样，我实际上没有此表示法.我读错了.

I have an AngularJS web application that looks like it is correctly sending JSON to the Tomcat server, but the server receives null values. This question didn't help because my property names are already lowercase, and this question didn't help because I've already got the @RequestBody notation. as pointed out in the comments, I don't actually have this notation. I was reading it wrong.

这是有问题的服务器方法:

Here is the server method in question:

@PostMapping(path="/kind/add")
public @ResponseBody String addNewKind(Kind kind) throws Exception {
    if (kind.getName() == null) {
        throw new Exception("Name not found.");
    }
    kindRepository.save(kind);
    return "Saved";
}

以下是它希望接收的Kind对象:

Here is the Kind object it expects to receive:

@Entity
public class Kind {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String name;
    @OneToMany(mappedBy="kind")
    private Set<Card> cards;

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Set<Card> getCards() {
        return cards;
    }

    public void setCards(Set<Card> cards) {
        this.cards = cards;
    }
}

以下是发出请求的方法:

Here is the method that makes the request:

var uri = 'http://localhost:8080/catalog/api/kind/';

function create(name) {
    var deferred = $q.defer();
    var data = {
        'name': name
    };
    $http({
        method: 'POST',
        url: uri + 'add',
        data: angular.toJson(data),
        headers: {
            'Content-Type': 'application/json; charset=UTF-8'
        }
    }).then(function(response) {
        deferred.resolve(response.data);
    }).catch(function(error) {
        console.error('Error while adding kind');
        deferred.reject(error);
    });
    return deferred.promise;
}

这是发送到服务器的JSON:

This is the JSON sent to the server:

{"name":"Something"}

NB 我以为我可以不发送id或cards参数而逃脱，因为id是自动生成的，而cards可以为空.但是，发送以下JSON时会得到相同的null结果:

N.B. I assumed that I can get away without sending id or cards parameters, since id is auto-generated and cards can be empty; however, I get the same null results when sending the following JSON:

{"id":0,"name":"Something","cards":[]}

这些是请求标头:

Accept:           application/json, text/plain, */*
Accept-Encoding:  gzip, deflate
Accept-Language:  en-US,en;q=0.5
Connection:       keep-alive
Content-Length:   20
Content-Type:     application/json; charset=UTF-8
Cookie:            __distillery=08c4ef1_752470a4-…ID=lr9remoqoi0ht13v1urq5lq8r7
Host:             localhost:8080
Referer:          http://localhost:8080/catalog/
User-Agent:       Mozilla/5.0 (Windows NT 10.0; …) Gecko/20100101 Firefox/57.0

这是在调试模式下查看kind对象参数时服务器收到的内容:

And this is what the server receives when I view the kind object argument in debug mode:

kind= Kind
    cards= null
    id= 0
    name= null

推荐答案

您需要使用

You need to use the @RequestBody annotation on your method. Your controller doesn't know what the body is, so your posted object is never bound (or never "makes it") to your method's Kind parameter.

@PostMapping(path="/kind/add")
public String addNewKind(@RequestBody Kind kind) throws Exception {
    if (kind.getName() == null) {
        throw new Exception("Name not found.");
    }
    kindRepository.save(kind);
    return "Saved";
}

如果您希望返回新的种类"，则希望您的控制器方法如下所示:

If you are expecting the new 'Kind' to be returned, you'd want your controller method to look like this:

@PostMapping(path="/kind/add")
public Kind addNewKind(@RequestBody Kind kind) throws Exception {
    if (kind.getName() == null) {
        throw new Exception("Name not found.");
    }
    return kindRepository.save(kind);
}

另一方面，我注意到您在写出JSON时使用了单引号.由于您要使用angular.toJson()转换数据，因此应该可以.如果您尝试通过直接发送JSON字符串进行交互，则通常将无法正常工作. JSON不使用单引号.

On a side note, I notice you are using single quotes in your JSON when you write it out. Since you are converting data with angular.toJson(), you should be OK there. If you are trying to interact by sending a JSON string directly, this will generally not work. JSON doesn't use single quotes.

这篇关于Spring POST接收具有空值的对象的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！