blocks|key|151244|text|如果我正确理解了this，您应该用参数化的构造函数替换默认的构造函数，因此必须描述用于调用构造函数的JSON键。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|151245|entityMap|0|LINK|mutability|MUTABLE|url|http://www.cowtowncoder.com/blog/archives/2011/07/entry_457.html^0|8|4|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

When I understand <a href="http://www.cowtowncoder.com/blog/archives/2011/07/entry_457.html" rel="nofollow">this</a> correctly, you replace the default constructor with a parameterized one and therefore have to describe the JSON keys which are used to call the constructor with.

blocks|key|4657530|text|如annotation+documentation中所述，注释指示参数名称用作属性名称而不做任何修改，但可以将其指定为非空值以指定不同的名称：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4657531|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/codehaus/jackson/blob/master/src/java/org/codehaus/jackson/annotate/JsonProperty.java^0|1|O|0|0^^$0|@$1|2|3|4|5|6|7|L|8|@]|9|@$A|M|B|N|1|O]]|C|$]]|$1|D|3|-4|5|6|7|P|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]]]

As precised in the <a href="https://github.com/codehaus/jackson/blob/master/src/java/org/codehaus/jackson/annotate/JsonProperty.java" rel="nofollow noreferrer">annotation documentation</a>, the annotation indicates that the argument name is used as the property name without any modifications, but it can be specified to non-empty value to specify different name:

blocks|key|4657587|text|Jackson必须知道以什么顺序将字段从JSON对象传递到构造函数。在Java中不能使用反射访问参数名称-这就是为什么您必须在注释中重复此信息的原因。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4657588|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Jackson has to know in what order to pass fields from a JSON object to the constructor.
It is not possible to access parameter names in Java using reflection - that's why you have to repeat this information in annotations.

blocks|key|4657608|text|因为Java字节码不保留方法或构造函数参数的名称。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4657609|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|D|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|E|8|@]|9|@]|A|$]]]|C|$]]

Because Java bytecode does not retain the names of method or constructor arguments.

blocks|key|151370|text|你可以简单地使用java.bean.ConstructorProperties注解-它不那么冗长，杰克逊也接受它。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|151371|++import+java.beans.ConstructorProperties;

++@ConstructorProperties({"answer","closed","language","interface","operation"})
++public+DialogueOutput(String+answer,+boolean+closed,+String+language,+String+anInterface,+String+operation)+{
++++this.answer+=+answer;
++++this.closed+=+closed;
++++this.language+=+language;
++++this.anInterface+=+anInterface;
++++this.operation+=+operation;
++}|code-block|syntax|javascript|151372|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

One can simply use java.bean.ConstructorProperties annotation - it's much less verbose and Jackson also accepts it. For example :

<pre><code> import java.beans.ConstructorProperties;

 @ConstructorProperties({"answer","closed","language","interface","operation"})
 public DialogueOutput(String answer, boolean closed, String language, String anInterface, String operation) {
 this.answer = answer;
 this.closed = closed;
 this.language = language;
 this.anInterface = anInterface;
 this.operation = operation;
 }
</code></pre>

blocks|key|151417|text|只是偶然发现了它，并在某个地方得到了答案。从2.7.0开始你可以使用下面的注解|type|unstyled|depth|inlineStyleRanges|entityRanges|data|151418|@JsonAutoDetect(fieldVisibility+=+JsonAutoDetect.Visibility.ANY)
public+class+Point+{
++++final+private+double+x;
++++final+private+double+y;

++++@ConstructorProperties({"x",+"y"})
++++public+Point(double+x,+double+y)+{
++++++++this.x+=+x;
++++++++this.y+=+y;
++++}
}|code-block|syntax|javascript|151419|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Just come across it and got an answer somewhere. you can use below annotation since 2.7.0 

<pre><code>@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY)
public class Point {
 final private double x;
 final private double y;

 @ConstructorProperties({"x", "y"})
 public Point(double x, double y) {
 this.x = x;
 this.y = y;
 }
}
</code></pre>

In Jackson, when you annotate a constructor with <code>@JsonCreator</code>, you must annotate its arguments with <code>@JsonProperty</code>. So this constructor

<pre><code>public Point(double x, double y) {
 this.x = x;
 this.y = y;
}
</code></pre>

becomes this:

<pre><code>@JsonCreator
public Point(@JsonProperty("x") double x, @JsonProperty("y") double y) {
 this.x = x;
 this.y = y;
}
</code></pre>

I don't understand why it's necessary. Can you please explain?

Why when a constructor is annotated with @JsonCreator, its arguments must be annotated with @JsonProperty?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在Jackson中，当你用@JsonCreator注释构造函数时，你必须用@JsonProperty注释它的参数。所以这个构造函数public Point(double x, double y) {    this.x = x;    this.y = y;}变成这样：@JsonCreatorpublic Point(...

问为什么当构造函数用@JsonCreator注解时，它的参数必须用@JsonProperty注解？
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问为什么当构造函数用@JsonCreator注解时，它的参数必须用@JsonProperty注解？
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