将复合Java对象转换为CSV

问题描述

我有一个对象，例如Response.java，看起来像以下内容:

I have an object, say Response.java that looks like the following:

class Response
{
   private User user;  // has firstName, lastName, age etc.
   private Address address; // has city, state, country etc.
   private OrderInfo orderInfo;  // has orderNumber, orderDate etc.

   // constuctors, getters/setters follow

}

我需要将这些对象的列表转换为csv，所以我的最终目标是:

I need to convert a List of these objects into csv, so my end goal is something like:

firstName, lastName, age, city, state, country, latitude, orderNumber, orderDate
john, doe, 25, dallas, tx, usa, somelat, 101, 08/17/2015
jane, doe, 21, atlant, ga, usa, somelat, 102, 08/15/2015

我尝试使用两个库-jackson(csv数据格式)，org.json(JsonArray)，但是我无法获得所需的结果.

I tried to use two libraries - jackson (csv dataformat), org.json (JsonArray), but i couldn't get the desired result.

这是我的杰克逊csv代码:

This is my jackson csv code:

Response response = getResponse();
final CsvMapper mapper = new CsvMapper();
final CsvSchema schema = mapper.schemaFor(Response.class);
final String csv = mapper.writer(schema).writeValueAsString(response);

有了杰克逊，我就得到了

With Jackson, i am getting

com.fasterxml.jackson.core.JsonGenerationException: CSV generator does not support Object values for properties

是否有一种方法可以按照我需要的方式将复合对象转换为csv(只是没有分组的json之类的字段)?

Is there a way to convert the composite object into csv in the way i need (just the fields without the json like grouping)?

推荐答案

所以我运行了一个在测试项目中使用的类似代码，看起来您将需要在所有对象(用户，地址，和OrderInfo).

So I ran similar code that you are using in a test project and it looks like you will need to use @JsonUnwrapped on all your objects (User, Address, and OrderInfo).

Jackson CSV不支持将对象作为属性，这就是为什么会出现该异常的原因.这是Github上的问题:杰克逊CSV对象属性问题

Jackson CSV doesn't support objects as properties which is why you got that exception. Here is the issue on Github: Jackson CSV Object properties issue

这是我用来验证的示例代码:

Here is sample code I used to verify this:

Test response = new Test();
response.setNum(1);
Stub s = new Stub();
s.setAge("12");
s.setName("Colin");
response.setS(s);
final CsvMapper mapper = new CsvMapper();
final CsvSchema schema = mapper.schemaFor(Test.class);
final String csv = mapper.writer(schema.withUseHeader(true)).writeValueAsString(response);
System.out.println(csv);

以上代码的输出如下:

num,age,name
1,12,Colin

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