java如何在Json字段之间添加行删除和适当的选项卡？

Question

我写了这段代码：

ObjectMapper mapper = new ObjectMapper();
ObjectWriter writer = mapper.writer(new DefaultPrettyPrinter());
try
{
    writer.writeValue(new File(jsonFile.getAbsolutePath()), jsonData);
}
catch (IOException e)
{
}

我得到的结果是：

{
  "type" : "aaa",
  "key" : {
    "key1" : "bbb",
    "key 2" : [ {
      "value" : "xx"
    }, {
      "value" : "sss"
    }, {
      "value" : "zzz"
    }]
  }
}

我希望内容是：

{
  "type" : "aaa",
  "key" : 
   {
    "key1" : "bbb",
    "key 2" :
    [
      {
        "value" : "xx"
      }, 
      {
        "value" : "sss"
      }, 
      {
        "value" : "zzz"
      }
    ]
  }
}

我希望它与任何括号中的下降线，和标签数量兼容。 如何在Json字段之间添加换行符和适当的选项卡

Answer 1

我不认为仅仅通过配置pretty printer就可以实现这一点，您必须为此实现自己的类。见https://fasterxml.github.io/jackson-core/javadoc/2.8/com/fasterxml/jackson/core/PrettyPrinter.html

Answer 2

要实现这样的格式，您需要实现自己的PrettyPrinter：

class ObjectArrayInNewLinePrettyPrinter extends DefaultPrettyPrinter {

    public ObjectArrayInNewLinePrettyPrinter() {
        super();
    }

    public ObjectArrayInNewLinePrettyPrinter(DefaultPrettyPrinter base) {
        super(base);
    }

    @Override
    public void writeStartObject(JsonGenerator g) throws IOException {
        _objectIndenter.writeIndentation(g, _nesting);
        super.writeStartObject(g);
    }

    @Override
    public void writeStartArray(JsonGenerator g) throws IOException {
        _arrayIndenter.writeIndentation(g, _nesting);
        super.writeStartArray(g);
    }

    @Override
    public DefaultPrettyPrinter createInstance() {
        return new ObjectArrayInNewLinePrettyPrinter(this);
    }
}

您可以按如下方式使用：

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.core.util.DefaultIndenter;
import com.fasterxml.jackson.core.util.DefaultPrettyPrinter;
import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.SerializationFeature;
import com.fasterxml.jackson.databind.json.JsonMapper;

import java.io.File;
import java.io.IOException;

public class JsonPrettyPrinterApp {
    public static void main(String[] args) throws IOException {
        File jsonFile = new File("./resource/test.json").getAbsoluteFile();

        DefaultPrettyPrinter printer = new ObjectArrayInNewLinePrettyPrinter();
        printer.indentArraysWith(new DefaultIndenter());

        JsonMapper mapper = JsonMapper.builder()
                .enable(SerializationFeature.INDENT_OUTPUT)
                .defaultPrettyPrinter(printer)
                .build();

        JsonNode root = mapper.readTree(jsonFile);

        mapper.writeValue(System.out, root);
    }
}

以上代码打印：

{
  "type" : "aaa",
  "key" : 
  {
    "key1" : "bbb",
    "key 2" : 
    [
      
      {
        "value" : "xx"
      },
      
      {
        "value" : "sss"
      },
      
      {
        "value" : "zzz"
      }
    ]
  }
}

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