杰克逊无法正常生成器模式反序列化

问题描述

我尝试处理请求

{
  "city": "city","date": "2020-08-26T12:15:54.428Z","time": {
      "sum":"123"
  }
}

我的目标是处理此请求。诀窍是，我尝试使用带有可选参数的Builder模式（根据有效Java。Joshua Bloch）。据我了解，我不必发送所有时间值。只需要总和。 我尝试通过邮递员将RequestBody中的Sport对象发送给我的控制器。

因此，我为Sport创建了POJO类：

@Entity
@Table(name = "sport")
@Getter
@Setter
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class Sport {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "date")
    private Date date;

    @Column(name = "city")
    private City city;

    @Type(type = "time")
    private Time time;
}

和 时间生成器：

package pl.project.model;

import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonPOJOBuilder;

@JsonDeserialize(builder = Time.Builder.class)
public class Time {
    private final String bike;
    private final String run;
    private final String sum;

    private Time(Builder builder) {
        bike = builder.bike;
        run = builder.run;
        sum = builder.sum;

    }

    @JsonPOJOBuilder(withPrefix = "")
    public static class Builder {

        String bike = "-";
        String run = "-";
        final String sum;

        Builder(String sum) {
            this.sum = sum;
        }

        Builder bike(String bike) {
            this.bike = bike;
            return this;
        }

        Builder run(String run) {
            this.run = run;
            return this;
        }

        Time build() {
            return new Time(this);
        }

    }
}

仍然出现错误：

JSON parse error: Cannot construct instance of `pl.project.model.Time$Builder` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator); nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot construct instance of `pl.project.model.Time$Builder` (although at least one Creator exists): cannot deserialize from Object value (no delegate- or property-based Creator)\n at [Source: (pushbackinputstream); line: 14,column: 7] (through reference chain: pl.project.model.Sport[\"time\"])"

我尝试了许多stackoverflow解决方案，但对我没有任何作用。

有人可以帮助我吗？

解决方法

Builder类必须具有以该属性命名的方法，和/或使用@JsonProperty来命名值。

使用@JsonProperty作为构造函数参数

@JsonPOJOBuilder(withPrefix = "")
public static class Builder {
    String bike = "-";
    String run = "-";
    final String sum;
    
    Builder(@JsonProperty("sum") String sum) { // must explicitly name the property
        this.sum = sum;
    }
    
    Builder bike(String bike) {
        this.bike = bike;
        return this;
    }
    
    Builder run(String run) {
        this.run = run;
        return this;
    }
    
    Time build() {
        return new Time(this);
    }
}

使用构建器的“ setter”方法

@JsonPOJOBuilder(withPrefix = "")
public static class Builder {
    String bike = "-";
    String run = "-";
    String sum;
    
    Builder sum(String sum) { // standard builder "setter" method
        this.sum = sum;
        return this;
    }
    
    @JsonProperty("bike") // must explicitly name for non-standard method name
    Builder setBicycle(String bike) {
        this.bike = bike;
        return this;
    }
    
    Builder run(String run) {
        this.run = run;
        return this;
    }
    
    Time build() {
        if (this.sum == null) // need to validate here,since property is otherwise optional
            throw new IllegalStateException("Required property missing: sum");
        return new Time(this);
    }
}