从Java中的JSON对象(JSON文件)中删除JSON节点

Question

我试图从JSON文件中删除几个节点。但我得到类强制转换异常时，我试图删除节点。java.lang.ClassCastException: class com.fasterxml.jackson.databind.node.TextNode cannot be cast to class com.fasterxml.jackson.databind.node.ObjectNode (com.fasterxml.jackson.databind.node.TextNode and com.fasterxml.jackson.databind.node.ObjectNode are in unnamed module of loader 'app')

我尝试了其他stackoverflow有用的链接，但不适合我。这是我写的代码。

public static void removeNodes(String filePath, String... nodeNames) throws IOException {
ObjectMapper objectMapper = new ObjectMapper();
JsonNode jsonNodes = objectMapper.readTree(new File(filePath));
for (JsonNode node : jsonNodes) {
((ObjectNode) node).remove(Arrays.asList(nodeNames));
}
objectMapper
.writerWithDefaultPrettyPrinter()
.writeValue(new File(filePath.split("\.")[0] + "_modified.json"), jsonNodes);
}

这是我正在读取的json文件。

{
"boolean_key": "--- truen",
"empty_string_translation": "",
"key_with_description": "Check it out! This key has a description! (At least in some formats)",
"key_with_line-break": "This translations containsna line-break.",
"nested": {
"deeply": {
"key": "Wow, this key is nested even deeper."
},
"key": "This key is nested inside a namespace."
},
"null_translation": null,
"pluralized_key": {
"one": "Only one pluralization found.",
"other": "Wow, you have %s pluralizations!",
"zero": "You have no pluralization."
},
"Dog_key": {
"nest": "Only one pluralization found.",
"sample_collection": [
"first item",
"second item",
"third item"
],
"Pest": "Only two pluralization found."
},
"simple_key": "Just a simple key with a simple message.",
"unverified_key": "This translation is not yet verified and waits for it. (In some formats we also export this status)"
}

打电话者:

import org.junit.jupiter.api.Test;
import org.junit.runner.RunWith;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;
import java.io.IOException;
// import static org.junit.jupiter.api.Assertions.*;
@RunWith(SpringRunner.class)
@SpringBootTest
class JSONUtilTest {
@Test
void removeNodes() throws IOException {
JSONUtil.removeNodes("D:\data\JSON_A.json", "pluralized_key", "Dog_key", "simple_key");
}
}

你能帮我找出造成这个问题的原因吗?

Answer 1

正如评论中提到的，您需要首先解析JSON，然后对其进行操作。

• 读文件。
• 用JSONParser的parse()方法解析并转换为JSONObject
• 删除你想要的节点

使用ObjectMapper的writerWithDefaultPrettyPrinter()方法，您可以获得适当的缩进并将其写入输出文件。

代码如下:

public static void removeNodes(String filePath, String... nodeNames) {
try (FileReader fileReader = new FileReader(filePath)) {
JSONParser jsonParser = new JSONParser();
JSONObject jsonObject = (JSONObject) jsonParser.parse(fileReader);
Stream<String> nodeStream = Stream.of(nodeNames);
nodeStream.forEach(jsonObject::remove);
ObjectMapper objectMapper = new ObjectMapper();
String jsonObjectPrettified = objectMapper.writerWithDefaultPrettyPrinter().writeValueAsString(jsonObject);
FileWriter fileWriter = new FileWriter(filePath.split("\.")[0] + "_modified.json");
fileWriter.write(jsonObjectPrettified);
fileWriter.close();
} catch (IOException | ParseException e) {
e.printStackTrace();
}
}