如何将List <string>转换为JsonNode。我想从List中删除元素

Question

我想创建一个"tags":"Engineering"带

的JSON节点

  JSON Example
    {"tags": ["Engineering","Pharmacy","Chemical"],
     "summary":"Science Streams",
     "produces": ["application\/json","application\/xml"]
    }
    ObjectMapper mapper = new ObjectMapper();
    List<Tags> tag = new ArrayList<Tags>();
    ArrayNode array = mapper.valueToTree(tags);
    ObjectNode objNode = mapper.valueToTree(array);
    JsonNode result = mapper.createObjectNode().set("tags", objNode );

当我使用它时，我收到以下错误：

com.fasterxml.jackson.databind.node.ArrayNode incompatible with com.fasterxml.jackson.databind.node.ObjectNode

如果我使用

，我会得到NullPointerException

for(String tag:tagList)

Answer 1

ArrayNode有一个remove方法，用于删除数组索引。这是一个解析JSON字符串的简单示例，从该JSON中的数组中删除元素并将其打印出来。

ObjectMapper mapper = new ObjectMapper();
JsonNode tree = mapper.readTree("{\"tags\": [\"Engineering\",\"Pharmacy\",\"Chemical\"]}");
ArrayNode tags = (ArrayNode) tree.get("tags");
tags.remove(1);
mapper.writeTree(mapper.getFactory().createGenerator(System.out), tree);

如果您想用单个字符串值替换数组，您可以这样做：

((ObjectNode) tree).set("tags", new TextNode("Engineering"));