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问题描述

我一直在尝试将对象序列化为CSV String ,但对象包含 List @JsonUnwrapped 列表对象上不起作用。



预期示例输出



  color,part.name\\\

red,gearbox \\\

red,door \\\

red,bumper

strong>实际输出:

  com.fasterxml.jackson.core.JsonGenerationException:无法识别的列'name':

这里是我的代码 :(大部分是2 POJO的) / p>

  import com.fasterxml.jackson.annotation.JsonAutoDetect; 
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import com.fasterxml.jackson.annotation.JsonRootName;
import com.fasterxml.jackson.dataformat.csv.CsvMapper;
import com.fasterxml.jackson.dataformat.csv.CsvSchema;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlElementWrapper;
import java.io.IOException;
import static java.util.Arrays.asList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

public class NestedWrapping {

@JsonRootName(Car)
@JsonInclude(JsonInclude.Include.NON_DEFAULT)
@JsonAutoDetect(fieldVisibility = JsonAutoDetect .Visibility.ANY,getterVisibility = JsonAutoDetect.Visibility.NONE,setterVisibility = JsonAutoDetect.Visibility.NONE)
@JsonPropertyOrder({color})
public static class Car {

@JsonProperty(color)
private String color;

@JsonFormat(shape = JsonFormat.Shape.STRING)
@JacksonXmlElementWrapper(useWrapping = false)
private List< Part>部分;

public String getColor(){
return color;
}

public void setColor(String color){
this.color = color;
}

public List< Part> getParts(){
return parts;
}

public void setParts(List< Part> parts){
this.parts = parts;
}

}

@JsonInclude(JsonInclude.Include.NON_DEFAULT)
@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY,getterVisibility = JsonAutoDetect。 Visibility.NONE,setterVisibility = JsonAutoDetect.Visibility.NONE)
@JsonPropertyOrder({
name
})
public static class Part {

@JsonProperty(name)
private String name;

public String getName(){
return name;
}

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

}

public static void main(String args []){
try {
Car car = new Car ;
car.setColor(red);
Part part1 = new Part();
part1.setName(geabox);
Part part2 = new Part();
part2.setName(door);
Part part3 = new Part();
part3.setName(bumper);
car.setParts(asList(part1,part2,part3));
System.out.println(serialized:+ serialize(car,Car.class,true));
} catch(IOException ex){
Logger.getLogger(NestedWrapping.class.getName())。log(Level.SEVERE,null,ex);
}
}

public static final synchronized String serialize(final Object object,final Class type,final Boolean withHeaders)throws IOException {
CsvMapper csvMapper = new CsvMapper );
CsvSchema csvSchema;
if(withHeaders){
csvSchema = csvMapper.schemaFor(type).withHeader();
} else {
csvSchema = csvMapper.schemaFor(type).withoutHeader();
}
return csvMapper.writer(csvSchema).writeValueAsString(object);
}

}

没有什么我试图似乎工作,我已阅读关于stackoverflow和github的每个,但我可以找到一个有效的解决方案。



对于任何无意义的注释,我遗漏了没有理由,如果你回答代码,请随时删除它们。

解决方案

从错误中,我想相信它与你的模式有关的 > > > > on Car 而不是name



您可能想在其中添加parts,但您会得到与<$ c相同的错误$ c>name不是该模式的一部分。



对代码进行了一些更改后,我能够序列化和反序列化 Car 对象。



部分



这里,经过一些其他修改后,单个String值,因此添加

  @JsonPropertyOrder({name})
public static class Part {
@JsonProperty(name)
私有字符串名称;

public Part(){
this();
}

public Part(String partJSON){
// TODO:取消序列化参数...它是一个序列化的部分字符串...
this.name = partJSON;
}


在这里,您需要实现一个方法,它将 List< Part> 手动转换为CSV可读格式。



这样的方法看起来像这样

  @JsonGetter $ b public String getPartString(){
String separator =;;
StringBuilder sb = new StringBuilder();

迭代器< Part> iter = this.parts.iterator();
while(iter.hasNext()){
part p = iter.next();
sb.append(p.getName());

if(iter.hasNext())
sb.append(separator);
}

return sb.toString();
}

此外,不要忘记修复类顶部的模式

  @JsonPropertyOrder({color,parts})
public static class Car {

@JsonProperty(color)
private String color;
@JsonProperty(parts)
private List< Part>部分;

public Car(){
this.parts = new ArrayList<>();
}

序列化

您可以更改 serialize 方法将类的类型作为通用类型参数,而不是显式的 Class 这样。

  public static final synchronized< T> String serialize(final T object,final Boolean withHeaders)throws IOException {
CsvMapper csvMapper = new CsvMapper();
CsvSchema csvSchema = csvMapper.schemaFor(object.getClass());

if(withHeaders){
csvSchema = csvSchema.withHeader();
} else {
csvSchema = csvSchema.withoutHeader();
}

return csvMapper.writer(csvSchema).writeValueAsString(object);
}

主要作家
$ b

现在,如果你序列化一个 Car ,你应该看到

  color,parts 
red,gearbox; door; bumper

主要读者



读取CSV字符串并循环遍历 Car.getParts c>

  Car car = mapper.readerFor(Car.class).with(csvSchema).readValue(csv); 

for(Part p:car.getParts()){
System.out.println(p.getName());
}





  gearbox 
door
bumper


I've been trying to serialize an object to a CSV String but the object contains a List and @JsonUnwrapped doesn't work on List objects.

Expected sample output:

color,part.name\n
red,gearbox\n
red,door\n
red,bumper

Actual output:

com.fasterxml.jackson.core.JsonGenerationException: Unrecognized column 'name':

Here is my code: (Most of it is the 2 POJO's)

import com.fasterxml.jackson.annotation.JsonAutoDetect;
import com.fasterxml.jackson.annotation.JsonFormat;
import com.fasterxml.jackson.annotation.JsonInclude;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import com.fasterxml.jackson.annotation.JsonRootName;
import com.fasterxml.jackson.dataformat.csv.CsvMapper;
import com.fasterxml.jackson.dataformat.csv.CsvSchema;
import com.fasterxml.jackson.dataformat.xml.annotation.JacksonXmlElementWrapper;
import java.io.IOException;
import static java.util.Arrays.asList;
import java.util.List;
import java.util.logging.Level;
import java.util.logging.Logger;

public class NestedWrapping {

@JsonRootName("Car")
@JsonInclude(JsonInclude.Include.NON_DEFAULT)
@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY, getterVisibility = JsonAutoDetect.Visibility.NONE, setterVisibility = JsonAutoDetect.Visibility.NONE)
@JsonPropertyOrder({"color"})
public static class Car {

    @JsonProperty("color")
    private String color;

    @JsonFormat(shape = JsonFormat.Shape.STRING)
    @JacksonXmlElementWrapper(useWrapping = false)
    private List<Part> parts;

    public String getColor() {
        return color;
    }

    public void setColor(String color) {
        this.color = color;
    }

    public List<Part> getParts() {
        return parts;
    }

    public void setParts(List<Part> parts) {
        this.parts = parts;
    }

}

@JsonInclude(JsonInclude.Include.NON_DEFAULT)
@JsonAutoDetect(fieldVisibility = JsonAutoDetect.Visibility.ANY, getterVisibility = JsonAutoDetect.Visibility.NONE, setterVisibility = JsonAutoDetect.Visibility.NONE)
@JsonPropertyOrder({
    "name"
})
public static class Part {

    @JsonProperty("name")
    private String name;

    public String getName() {
        return name;
    }

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

}

public static void main(String args[]) {
    try {
        Car car = new Car();
        car.setColor("red");
        Part part1 = new Part();
        part1.setName("geabox");
        Part part2 = new Part();
        part2.setName("door");
        Part part3 = new Part();
        part3.setName("bumper");
        car.setParts(asList(part1, part2, part3));
        System.out.println("serialized: " + serialize(car, Car.class, true));
    } catch (IOException ex) {
        Logger.getLogger(NestedWrapping.class.getName()).log(Level.SEVERE, null, ex);
    }
}

public static final synchronized String serialize(final Object object, final Class type, final Boolean withHeaders) throws IOException {
    CsvMapper csvMapper = new CsvMapper();
    CsvSchema csvSchema;
    if (withHeaders) {
        csvSchema = csvMapper.schemaFor(type).withHeader();
    } else {
        csvSchema = csvMapper.schemaFor(type).withoutHeader();
    }
    return csvMapper.writer(csvSchema).writeValueAsString(object);
}

}

Nothing I try seems to work, I've read every post on stackoverflow and github about the topic but I can't find a working solution.

Sorry about any pointless annotations that I've left behind for no reason and if you answer with code, please feel free to remove them.

解决方案

From the error, I would like to believe that it has something to do with your schema for a Car, which has the columns of {"color"} taken from @JsonPropertyOrder on Car and not a "name" value.

You probably want to add "parts" in there, but you would get the same error that "name" is not part of that schema.

After a few changes to your code, I was able to serialize and deserialize a Car object.

Part

Here, after some other changes it needed a constructor with a single String value, so add that

@JsonPropertyOrder({"name"})
public static class Part {
    @JsonProperty("name")
    private String name;

    public Part() {
        this("");
    }

    public Part(String partJSON) {
        // TODO: Unserialize the parameter... it is a serialized Part string...
        this.name = partJSON;
    }

Car

Here, you will need to implement a method that will convert the List<Part> into a CSV-readable format manually.

Such a method would look like this

@JsonGetter("parts")
public String getPartString() {
    String separator = ";";
    StringBuilder sb = new StringBuilder();

    Iterator<Part> iter = this.parts.iterator();
    while (iter.hasNext()) {
        Part p = iter.next();
        sb.append(p.getName());

        if (iter.hasNext())
            sb.append(separator);
    }

    return sb.toString();
}

Also, don't forget to fix the schema at the top of the class

@JsonPropertyOrder({"color", "parts"})
public static class Car {

    @JsonProperty("color")
    private String color;
    @JsonProperty("parts")
    private List<Part> parts;

    public Car() {
        this.parts = new ArrayList<>();
    }

serialize

You can change your serialize method to take the type of the class as a generic type parameter instead of an explicit Class like so.

public static final synchronized <T> String serialize(final T object, final Boolean withHeaders) throws IOException {
    CsvMapper csvMapper = new CsvMapper();
    CsvSchema csvSchema = csvMapper.schemaFor(object.getClass());

    if (withHeaders) {
        csvSchema = csvSchema.withHeader();
    } else {
        csvSchema = csvSchema.withoutHeader();
    }

    return csvMapper.writer(csvSchema).writeValueAsString(object);
}

main - writer

Now, if you serialize a Car, you should see

color,parts
red,gearbox;door;bumper

main - reader

And reading that CSV string and looping over the Car.getParts()

Car car = mapper.readerFor(Car.class).with(csvSchema).readValue(csv);

for (Part p : car.getParts()) {
    System.out.println(p.getName());
}
gearbox
door
bumper

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09-01 14:58