我正在尝试用Java创建一个JSON收件箱对象。
public class GetContacts extends HttpServlet {
public void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException{
try{
String list = req.getParameter("list");
String profileId = "27";
//Accessing driver from the JAR file
Class.forName ("com.mysql.jdbc.Driver").newInstance();
//Connect to Clockie's database
Connection con = DriverManager.getConnection ("jdbc:mysql://localhost:3306/cdatabase", "root", "root");
//Here we create our query
String sql =
"SELECT * " +
"FROM messages " +
"WHERE profileId = ?";
PreparedStatement statement = con.prepareStatement(sql);
statement.setString(1, profileId);
ResultSet result = statement.executeQuery();
JSONArray messages = new JSONArray();
while(result.next()){
JSONObject message = new JSONObject();
message.put("to", result.getString("to"));
message.put("from", result.getString("from"));
message.put("message", result.getString("message"));
message.put("profileId", profileId);
messages.put(message);
}
System.out.println(messages.toString());
resp.setContentType("text/javascript");
PrintWriter out = resp.getWriter();
String output = req.getParameter("callback") + "(" + messages.toString() + ");";
out.write(output);
out.close();
}
catch(Exception e){
e.printStackTrace();
}
}
}
但是我收到以下错误消息:
本地变量消息尚未初始化
我做错了什么?
我使用的JSON类是http://www.json.org/java/
中的原始类BTW,我正在使用Eclipse作为我的IDE
好的,我想我找到了问题所在。我尝试导出Jar文件时添加的JSON库出错了。并且错误出现在JSONArray类中。如何将JSON库导出到Eclipse中的jar文件?
这就是我做的并得到一些警告(警告在JSONArray类中):
Ok created a new project and right click -> export -> choose Jar Files (under java folder) -> marked both .classpath and .project in the right rectangle -> I selected a random destination folder with the filname org.json.jar. When I did this i got some warnings
别介意问题的位置。我试图将变量消息变量messagesss
定义为JSONArray obj。 message
而非messagessss
我仍然遇到同样的错误。但是我如何纠正这个问题呢?
java类在一个名为messages的包下,这是问题吗?
答案 0 :(得分:0)
如果clean + build无法帮助您尝试刷新项目或重新启动IDE。我在Eclipse中复制了这段代码,没有任何问题。