Question

我正在将Spring Boot与预期的依赖项（Jackson，Hibernate等）一起使用。

我有一个名为Buildings的表，其中Unit，Number，Street等都是列。但是我更喜欢解析它，并将其作为我创建的名为“ StreetAddress”的类返回。

发送此JSON时，出现错误。

"address": {
    "unit":"0101",
    "number":"19",
    "suffix":"STREET",
    "suburb":"Example",
    "state":"EXP",
    "streetName":"Example",
    "postCode":"400"
}

这是错误：

Cannot construct instance of `com.App.Entity.Helpers.StreetAddress` (no Creators, like default construct, exist): cannot deserialize from Object value (no delegate- or property-based Creator)

我在建筑模型中将其作为setAddress。有什么注释可以告诉Jackson如何正确解析吗？

private String subunit;
private Integer number;
private String streetname;
private String suffix;
private String suburb;
private String state;
private Integer postcode;    

public void setAddress(StreetAddress address) {
        this.subunit = address.getUnit();
        this.number = address.getNumber();
        this.streetname = address.getStreetName();
        this.suffix = address.getSuffix().toString();
        this.suburb = address.getSuburb();
        this.state = address.getState().toString();
        this.postcode = address.getPostCode();
    }

说明：

public class StreetAddress {
private String unit;
private Integer number;
private String streetname;
private StreetSuffix suffix;
private String suburb;
private AUState state;
private Integer postcode;

public StreetAddress(String unit, int number, String street, StreetSuffix suffix, String suburb, AUState state, int postcode) {
    this.unit = unit;
    this.number = number;
    this.streetname = street;
    this.suffix = suffix;
    this.suburb = suburb;
    this.state = state;
    this.postcode = postcode;
}

public String getUnit() {
    return unit;
}

public Integer getNumber() {
    return number;
}

public String getStreetName() {
    return streetname;
}

public String getSuffix() {
    return suffix.toString();
}

public String getSuburb() {
    return suburb;
}

public AUState getState() {
    return state;
}

public Integer getPostCode() {
    return postcode;
}

}

Answer 1

该错误消息指出，杰克逊不知道如何创建StreetAddress类型的对象，因为找不到合适的构造函数。 Jackson期望使用无参数的构造函数（在这种情况下，它将通过分配字段或调用setter来传递JSON数据），或者期望带有注释的构造函数，该注释告诉Jackson应该将哪个JSON属性传递给哪个参数。

解决此问题的最简单方法是不声明构造函数，而是将字段设为公开字段：

public class StreetAddress {
    public String unit;
    // ... more fields here
}

或者，您可以将字段设为私有，但为每个字段声明一个setter：

public class StreetAddress {
    private String unit;
    // ... more fields here

    public void setUnit(String unit) {
        this.unit = unit;
    }
    // ... more setters here
}

在春天序列化嵌套类到表行

1 个答案: