Spring MVC 中的 Java 到 JSON 对象映射导致 400 Bad request 错误

Question

当我在应用程序引擎中从我的应用程序接收 json 数据时遇到了一些麻烦，在某些情况下我收到的 json 是空的，并且在我的应用程序的日志查看器中出现以下内容

    2014-07-03 16:46:21.193 /service/concentraciondeptos/ 400 43ms 0kb Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.1916.153 Safari/537.36 module=default version=2
181.48.97.68 - - [03/Jul/2014:14:46:21 -0700] "GET /service/concentraciondeptos/ HTTP/1.1" 400 146 - "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/35.0.1916.153 Safari/537.36" "Instance ID" ms=44 cpu_ms=80 cpm_usd=0.000016 app_engine_release=1.9.6 trace_id=e2164f3bbeb2302c384164569b22b8dd 

这是我的代码

package com.servinfo.services.controller;

import java.sql.ResultSet;
import java.util.ArrayList;
import java.util.List;

import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.ResponseBody;

import com.servinfo.database.Manager;
import com.servinfo.services.AbstractController;
import com.servinfo.services.entity.ResponseObject;
import com.servinfo.services.entity.afe.ConcentracionDeptos;

@Controller
@RequestMapping("service/concentraciondeptos/*")
public class ConcentracionDeptosController {

    // private static final Logger log = Logger.getLogger("AreaTController");

    protected final static String RESPONSE_FORMAT = "application/json";

    private final static String GET = "";

    private static String STATE = "";

    private static String MESSAGE = "";


    @RequestMapping(value = GET, method = RequestMethod.GET, produces = RESPONSE_FORMAT)
    public @ResponseBody
    ResponseEntity<ResponseObject> getPoint() {

        if (getData().isEmpty()) {
            STATE = "ERROR";
            MESSAGE = ResponseObject.MSG_EMPTY;
        }

        // log.warning("Servicio areat");
        ResponseObject response = new ResponseObject(STATE, MESSAGE, getData());

        if (response.getStatus().equals("OK")) {
            return new ResponseEntity<ResponseObject>(response,
                    AbstractController.getHeader(), HttpStatus.OK);
        }

        return new ResponseEntity<ResponseObject>(response,
                AbstractController.getHeader(), HttpStatus.BAD_REQUEST);

    }

    public List<ConcentracionDeptos> getData() {
        STATE = "ERROR";
        MESSAGE = ResponseObject.MSG_ERROR;
        int intContador = 0;

        List<ConcentracionDeptos> result = new ArrayList<ConcentracionDeptos>();
        try {
            String sql = "select depto.coddane "
                    + ""
                    + "from departamentos as depto, proyecto as p, aporte_depto as apdepto,"
                    + "aporte_muni as apomuni, ciudades as ciu"
                    + " "
                    + "where apdepto.nit = p.nit and apdepto.id_proyecto = p.id "
                    + "and apdepto.coddane_depto = depto.coddane and apomuni.nit = p.nit "
                    + "and apomuni.id_proyecto = p.id and apomuni.coddane_ciudad = ciu.coddane";

            Manager mng = new Manager();
            ResultSet rs = mng.executeQuery(sql);
            if (rs.first()) {
                rs.beforeFirst();
                STATE = "OK";
                MESSAGE = ResponseObject.MSG_SUCCESS;
            } else {
                Thread.sleep(200);
                rs = mng.executeQuery(sql);
                if (rs.first()) {
                    rs.beforeFirst();
                    STATE = "OK";
                    MESSAGE = ResponseObject.MSG_SUCCESS;
                } else {
                    STATE = "ERROR";
                    MESSAGE = ResponseObject.MSG_ERROR;
                }
            }
            ConcentracionDeptos obEntity = new ConcentracionDeptos();
            while (rs.next()) {
                intContador++;
                obEntity.setCoddane(rs.getString("coddane"));
            }
            obEntity.setCantidadP(Integer.toString(intContador));
            result.add(obEntity);
            rs.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        return result;
    }
}

当我在 mysql 中执行 sql 命令时，我检索到了正确的信息。 这是连接代码

import java.sql.*;
import com.google.appengine.api.utils.SystemProperty;

public class Manager {

    public ResultSet executeQuery(String sql){

        try{
            String url = null;
            if (SystemProperty.environment.value() == SystemProperty.Environment.Value.Production) {
                Class.forName("com.mysql.jdbc.GoogleDriver");
                url = "jdbc:google:mysql://ID:App ID/DB?user=root";
            } else {
                Class.forName("com.mysql.jdbc.Driver");
                url = "jdbc:mysql://IP:3306/afe_services?user=root&password=****";
            }

            Connection conn = DriverManager.getConnection(url);
            ResultSet rs = conn.createStatement().executeQuery(sql);
            return rs;

        }catch(Exception e){
            e.printStackTrace();
        }
        return null;
    }
}

我做错了什么？

谢谢。

Answer 1

编辑 2：

经过长时间的讨论，这里的问题是没有数据库连接和会话维护。

因此当你调用数据库时，它会失败，因此会出现无连接错误。

您需要按照spring.io/guides 页面中的说明设置连接。 网络教程给出了深入的数据库连接和维护说明。

如需快速解释或脏版本设置，您可以查看http://spring.io/guides/gs/relational-data-access/