我想用一个字符串数组创建一个Json，每个字符串看起来像： ＆＃34; id.categoryvalue.subcatvalue.subsubcatvalue.score＆＃34; 结果应如下所示：
{
"user-id": "u42",
"categories": [
{
"category": "value",
"subcats": [
{
"subcat": "value",
"subsubcats": [
{
"subsubcat": "value",
"score": 47
}
]
}
]
}
]
}
我不想复制同一类别中的值，解决问题的有效方法是什么？谢谢！
答案 0 :(得分：0)
假设输入格式保持不变，您可以执行以下操作：
Tokenize输入字符串，将其与. Map并设置适当的值）String解析器JSON
下面的例子演示了它：
public static void main(String[] args) throws Exception{
Map<String, Object> result = convertToMap("id.categoryvalue.subcatvalue.subsubcatvalue.score");
System.out.println(new ObjectMapper().writeValueAsString(result));
}
public static Map<String, Object> convertToMap(String input){
Map<String, Object> result = new LinkedHashMap<>();
String[] tokens = input.split("\\.");
if(tokens.length < 5){
//Invalid string, return
throw new IllegalArgumentException("Insufficient tokens");
}
//Add user id
result.put("user-id", tokens[0]);
//Add category
Map<String, Object> category = new LinkedHashMap<>();
category.put("category", tokens[1]);
//Add sub category
Map<String, Object> subCategory = new LinkedHashMap<>();
subCategory.put("subcat", tokens[2]);
//Add nested category
Map<String, Object> nestedSubCategory = new LinkedHashMap<>();
nestedSubCategory.put("subsubcat", tokens[3]);
nestedSubCategory.put("score", Integer.parseInt(tokens[4]));
subCategory.put("subcats", Arrays.asList(new Map[] {nestedSubCategory}));
category.put("subcats", Arrays.asList(new Map[] {subCategory}));
result.put("categories", Arrays.asList(new Map[] {category}));
return result;
}
答案 1 :(得分：0)
使用Gson，您可以使用对象模型方式或流式方式生成JSON。第一个需要在以强类型方式（见下文）或弱类型方式生成JSON之前构建整个对象（如Darshan Mehta建议的那样 - 他使用基于Java映射的弱对象）
将给定数据分解为几个数据包类，构造这些类的对象，只需调用Gson：
public final class ObjectModelDemo {
private ObjectModelDemo() {
}
public static void main(final String... args) {
final String[] tokens = "id31.english.B1.Animals.11".split("\\.");
if ( tokens.length != 5 ) {
throw new IllegalArgumentException("Not 5 tokens in " + "id31.english.B1.Animals.11");
}
final String userId = tokens[0];
final String category = tokens[1];
final String subcategory = tokens[2];
final String subsubcategory = tokens[3];
final int score = parseInt(tokens[4]);
final User user = new User(
userId,
singletonList(new Category(
category,
singletonList(new Subcategory(
subcategory,
singletonList(new Subsubcategory(subsubcategory, score))
))
))
);
final Gson gson = new GsonBuilder().create();
out.println(gson.toJson(user));
}
private static final class User {
@SerializedName("user-id")
private final String userId;
@SerializedName("categories")
private final List<Category> categories;
private User(final String userId, final List<Category> categories) {
this.userId = userId;
this.categories = categories;
}
}
private static final class Category {
@SerializedName("category")
private final String category;
@SerializedName("subcats")
private final List<Subcategory> subcategories;
private Category(final String category, final List<Subcategory> subcategories) {
this.category = category;
this.subcategories = subcategories;
}
}
private static final class Subcategory {
@SerializedName("subcat")
private final String subcategory;
@SerializedName("subsubcats")
private final List<Subsubcategory> subsubcategories;
private Subcategory(final String subcategory, final List<Subsubcategory> subsubcategories) {
this.subcategory = subcategory;
this.subsubcategories = subsubcategories;
}
}
private static final class Subsubcategory {
@SerializedName("subsubcat")
private final String subsubcategory;
@SerializedName("score")
private final int score;
private Subsubcategory(final String subsubcategory, final int score) {
this.subsubcategory = subsubcategory;
this.score = score;
}
}
}
此类数据包称为DTO（data-transfer objects），旨在映射Java对象及其各自的JSON表示。这为Java编译器提供了非常强大的编译时控制支持。这种方法的缺点是必须在任何JSON生成开始之前收集所有数据（通常这对于对内存敏感的应用程序非常重要）。但是，对于您的情况，这可能会更容易，也可能是最容易的。
输出：
{ “用户ID”： “ID31”， “类别”：[{ “类别”： “英语”， “subcats”：[{ “SUBCAT”： “B1”， “subsubcats”：[{“subsubcat “：” 动物”， “分数”：11}]}]}]}
基于将JSON中间写入目标的替代方法。这种方法是一种更复杂的数据推送方法，但从内存消耗的角度来看它更有效（甚至更多，你可以使用这种方法轻松生成无限的JSON，但我怀疑你会遇到这样的情况:)）。
public static void main(final String... args)
throws IOException {
final String[] tokens = "id21.english.B2.Insects.24".split("\\.");
if ( tokens.length != 5 ) {
throw new IllegalArgumentException("Not 5 tokens in " + "id21.english.B2.Insects.24");
}
final String userId = tokens[0];
final String category = tokens[1];
final String subcategory = tokens[2];
final String subsubcategory = tokens[3];
final int score = parseInt(tokens[4]);
final JsonWriter jsonWriter = new JsonWriter(new OutputStreamWriter(out));
writeUser(jsonWriter, userId, category, subcategory, subsubcategory, score);
jsonWriter.flush();
// do not invoke jsonWriter.close() -- let the caller decide what to do
}
private static void writeUser(final JsonWriter jsonWriter, final String userId, final String category, final String subcategory,
final String subsubcategory, final int score)
throws IOException {
jsonWriter.beginObject();
jsonWriter.name("user-id");
jsonWriter.value(userId);
jsonWriter.name("categories");
writeCategories(jsonWriter, category, subcategory, subsubcategory, score);
jsonWriter.endObject();
}
private static void writeCategories(final JsonWriter jsonWriter, final String category, final String subcategory, final String subsubcategory,
final int score)
throws IOException {
jsonWriter.beginArray();
jsonWriter.beginObject();
jsonWriter.name("category");
jsonWriter.value(category);
jsonWriter.name("subcats");
writeSubcategories(jsonWriter, subcategory, subsubcategory, score);
jsonWriter.endObject();
jsonWriter.endArray();
}
private static void writeSubcategories(final JsonWriter jsonWriter, final String subcategory, final String subsubcategory, final int score)
throws IOException {
jsonWriter.beginArray();
jsonWriter.beginObject();
jsonWriter.name("subcat");
jsonWriter.value(subcategory);
jsonWriter.name("subsubcats");
writeSubsubcategories(jsonWriter, subsubcategory, score);
jsonWriter.endObject();
jsonWriter.endArray();
}
private static void writeSubsubcategories(final JsonWriter jsonWriter, final String subsubcategory, final int score)
throws IOException {
jsonWriter.beginArray();
jsonWriter.beginObject();
jsonWriter.name("subsubcat");
jsonWriter.value(subsubcategory);
jsonWriter.name("score");
jsonWriter.value(score);
jsonWriter.endObject();
jsonWriter.endArray();
}
}
注意数据如何写入输出流：一旦有足够的已知数据，就可以轻松将其刷新到输出流。是的，这是一种更难写的方法，但这是另一种选择。
输出：
{ “用户ID”： “ID21”， “类别”：[{ “类别”： “英语”， “subcats”：[{ “SUBCAT”： “B2”， “subsubcats”：[{“subsubcat “：” 昆虫”， “分数”：24}]}]}]}