javascript - 解析不同对象类型的json数组

Question

我正在尝试将不同类型的数组从 Javascript 发送到 Java servlet。

用于生成和发送数据的 Javascript 代码是:

function sendDataOnButtonPress()
{
  var obj1 = {'key_11': "val_11", 'key_12': "val_12"};
  var obj2 = {'key_21': "val_21", 'key_22': "val_22"};
  var myArray = [obj1, obj2];

  var params = {
      data: JSON.stringify(myArray)
  };

  $.post("serv1", $.param(params), function(response) {
    console.log("response = " + response);
  });
}

用于处理该数据的Java代码是:

import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.fasterxml.jackson.databind.ObjectMapper;

@WebServlet("/serv1")
public class serv1 extends HttpServlet {
  private static final long serialVersionUID = 1L;

    public serv1() {
        super();
        // TODO Auto-generated constructor stub
    }

  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    String data = request.getParameter("data");
    //System.out.println(data);

    ObjectMapper mapper = new ObjectMapper();
    Object[] objs = mapper.readValue(data, Object[].class);
    System.out.println(objs[0]);

    PrintWriter writer1 = response.getWriter();
    String htmlRespone = "Dummy response";
    writer1.println(htmlRespone);

  }

  /**
   * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
   */
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    // TODO Auto-generated method stub
    doGet(request, response);
  }

}

尽管 System.out.println(objs[0]); 行正确输出了数组的第一个对象，但我无法弄清楚如何访问该对象的属性:

System.out.println(objs[0]["key_11"]);

无法编译。

那么，我的问题是如何正确解析Java内部的javascript发送的数据？

我也愿意使用 Jackson 以外的任何 json 解析库。

Answer 1

您可以通过以下方式获取。父类(super class) Object 无法获取您指定的值，因此会出现编译器错误。

为了了解具体类型，我打印了对象的类。在本例中它是一个 LinkedHashMap。因此，我安全地将 obj[0] 转换到其中。一旦我有了 map ，我总是可以通过查找键来获取值。希望这有帮助

String data = "[{\"key_11\": \"val_11\", \"key_12\": \"val_12\"}, {\"key_21\": \"val_21\", \"key_22\": \"val_22\"}]";
ObjectMapper mapper = new ObjectMapper();
Object[] objs = mapper.readValue(data, Object[].class);
System.out.println(objs[0].getClass().getName());

LinkedHashMap<String, Object> keyValues = (LinkedHashMap) objs[0];

System.out.println(keyValues.get("key_11"));