如何使用 javax.json lib 迭代更多 JsonObject

Question

这是我的第一篇文章，谢谢。

我正在使用 javax.json 库来读取包含 Json 的导入 file.txt。

这是正文：

    [{
            "role" : "role1",
            "db" : "db_admin",
            "flag" : false,
            "roles" : [
                    {
                            "role" : "role",
                            "db" : "db_admin"
                    }
            ],
            "inRoles" : [
                    {
                            "role" : "role",
                            "db" : "db_admin"
                    }
            ]
    },
    {
            "role" : "role2",
            "db" : "db_admin",
            "flag" : false,
            "roles" : [
                    {
                            "role" : "role",
                            "db" : "db_admin"
                    }
            ],
            "inRoles" : [
                    {
                            "role" : "role",
                            "db" : "db_admin"
                    }
            ]
    },
    {
            "role" : "role3",
            "db" : "db_admin",
            "flag" : false,
            "roles" : [
                    {
                            "role" : "role",
                            "db" : "db_admin"
                    }
            ],
            "inRoles" : [
                    {
                            "role" : "role",
                            "db" : "db_admin"
                    }
            ]
    }]

现在，我做了一些尝试，但我只能读取第一个对象。 这是我读取 first JsonArray 的代码：

//I read all line and put them into StringBuilder and then in a unique String
String json = sbJson.toString();
  JsonReader jsonreader = Json.createReader(new StringReader(json));
  // Get the JsonObject structure from JsonReader.
  JsonObject jsonobject = jsonreader.readObject();
  jsonreader.close();

  // read json array
  JsonArray jsonarray = jsonobject.getJsonArray("roles");
  JsonObject value = jsonarray.getJsonObject(0);
  String roles_role = value.getString("role");
  String roles_db = value.getString("db");


  jsonarray = jsonobject.getJsonArray("inRoles");
  value = jsonarray.getJsonObject(0);
  String inheritedRoles_role = value.getString("role");
  String inheritedRoles_db = value.getString("db");

所以我可以从第一个 JsonObject 中获取所有元素，但我需要其他元素，并且我尝试了更多解决方案，但它们对我不起作用...

Answer 1

您需要执行一个 for 循环才能读取所有内容。这是你可以做到的方法

static String json = "[{\n"
            + "            \"role\" : \"role1\",\n"
            + "            \"db\" : \"db_admin\",\n"
            + "            \"flag\" : false,\n"
            + "            \"roles\" : [\n"
            + "                    {\n"
            + "                            \"role\" : \"role\",\n"
            + "                            \"db\" : \"db_admin\"\n"
            + "                    }\n"
            + "            ],\n"
            + "            \"inRoles\" : [\n"
            + "                    {\n"
            + "                            \"role\" : \"role\",\n"
            + "                            \"db\" : \"db_admin\"\n"
            + "                    }\n"
            + "            ]\n"
            + "    },\n"
            + "    {\n"
            + "            \"role\" : \"role2\",\n"
            + "            \"db\" : \"db_admin\",\n"
            + "            \"flag\" : false,\n"
            + "            \"roles\" : [\n"
            + "                    {\n"
            + "                            \"role\" : \"role\",\n"
            + "                            \"db\" : \"db_admin\"\n"
            + "                    }\n"
            + "            ],\n"
            + "            \"inRoles\" : [\n"
            + "                    {\n"
            + "                            \"role\" : \"role\",\n"
            + "                            \"db\" : \"db_admin\"\n"
            + "                    }\n"
            + "            ]\n"
            + "    },\n"
            + "    {\n"
            + "            \"role\" : \"role3\",\n"
            + "            \"db\" : \"db_admin\",\n"
            + "            \"flag\" : false,\n"
            + "            \"roles\" : [\n"
            + "                    {\n"
            + "                            \"role\" : \"role\",\n"
            + "                            \"db\" : \"db_admin\"\n"
            + "                    }\n"
            + "            ],\n"
            + "            \"inRoles\" : [\n"
            + "                    {\n"
            + "                            \"role\" : \"role\",\n"
            + "                            \"db\" : \"db_admin\"\n"
            + "                    }\n"
            + "            ]\n"
            + "    }]";

    public static void main(String[] args) throws Exception {
        JsonReader jsonreader = Json.createReader(new StringReader(json));
        // Get the JsonObject structure from JsonReader.
        JsonArray jsonArray = jsonreader.readArray();
        jsonreader.close();

        for(Object j :jsonArray.toArray()){
            System.out.println("j:"+ j);
        }
    }

这就是我本地的样子

--- exec-maven-plugin:1.5.0:exec (default-cli) @ hackerrank ---
j:{"role":"role1","db":"db_admin","flag":false,"roles":[{"role":"role","db":"db_admin"}],"inRoles":[{"role":"role","db":"db_admin"}]}
j:{"role":"role2","db":"db_admin","flag":false,"roles":[{"role":"role","db":"db_admin"}],"inRoles":[{"role":"role","db":"db_admin"}]}
j:{"role":"role3","db":"db_admin","flag":false,"roles":[{"role":"role","db":"db_admin"}],"inRoles":[{"role":"role","db":"db_admin"}]}
------------------------------------------------------------------------
BUILD SUCCESS
------------------------------------------------------------------------
Total time:  0.979 s

如果我使用的是什么 javax json，我有一个 mvn 项目并在下面使用了依赖项

<dependency>
  <groupId>javax.json</groupId>
  <artifactId>javax.json-api</artifactId>
  <version>1.1.4</version>
  <type>jar</type>
</dependency>
<dependency>
    <groupId>org.glassfish</groupId>
    <artifactId>javax.json</artifactId>
    <version>1.1.4</version>
</dependency>

另外如果你只想从数组中获取一个对象，可以查看https://stackoverflow.com/a/8481439/175554