我正在使用亚马逊的云服务开发一个 web 应用程序，我需要使用 JSON 对象。我的项目是如何设置的，我有一个 HTML 表单，用户将在其中填写他们的信息并提交。提交后，数据将被放入在线数据库，并向他们发送确认电子邮件。在我可以将数据提交到数据库之前，我需要将所有数据放入一个 JSON 对象中。我用 Java 完成的 servlet 如下所示：
public class FormHandling extends HttpServlet {
//doGet function
public void doGet (HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
// In this part of the code I take in the user data and build an HTML
// page and return it to the user
// Create String Mapping for User Data object
Map<String,Object> userData = new HashMap<String,Object>();
// Map the names into one struct. In the code below we are creating
// values for the nameStruct from the information the user has
// submitted on the form.
Map<String,String> nameStruct = new HashMap<String,String>();
nameStruct.put("fName", request.getParameter("fname"));
nameStruct.put("lName", request.getParameter("lname"));
nameStruct.put("mInit", request.getParameter("minit"));
// Map the three email's together (providing there are 3).
// This is the same logic as the names.
Map<String,String> emailStruct = new HashMap<String,String>();
emailStruct.put("email", request.getParameter("email1"));
emailStruct.put("email", request.getParameter("email2"));
emailStruct.put("email", request.getParameter("email3"));
// Put Name Hash Value Pair inside User Data Object
userData.put("name", nameStruct);
userData.put("emails", emailStruct);
userData.put("age", 22);
// Create the Json data from the userData
createJson(userData);
// Close writer
out.close();
}
public File createJson(Map<String,Object> userData)
throws JsonGenerationException, JsonMappingException, IOException {
File user = new File("user.json");
// Create mapper object
ObjectMapper mapper = new ObjectMapper();
// Add the userData information to the json file
mapper.writeValue(user, userData);
return user;
}
}
当我使用此代码提交表单时，我收到以下错误消息：
java.lang.NoClassDefFoundError: com/fasterxml/jackson/annotation/JsonAutoDetect com.fasterxml.jackson.databind.introspect.VisibilityChecker$Std.(VisibilityChecker.java:169) com.fasterxml.jackson.databind.ObjectMapper.(ObjectMapper.java :197) edu.tcnj.FormHandling.createJson(FormHandling.java:115) edu.tcnj.FormHandling.doGet(FormHandling.java:104) edu.tcnj.FormHandling.doPost(FormHandling.java:131) javax.servlet.http .HttpServlet.service(HttpServlet.java:641) javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
现在我知道这个错误意味着它没有找到 Jackson 数据绑定库。我在 Eclipse 中进行开发，并且我知道构建路径有时会混乱，因此我还将库放在 WebContent\WEB-INF\lib 文件夹中。这解决了我之前遇到的问题。但是，这一次似乎并没有解决我的问题。我什至打开了 jar 文件以实际检查所需的库和类是否存在，它们确实存在。我已经尝试过搜索并寻找包含库的不同方法，但似乎没有任何效果。