android解析json报空指针异常。

package com.student.activity;



import java.net.URI;

import java.util.ArrayList;

import java.util.HashMap;

import java.util.List;



import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.client.HttpClient;

import org.apache.http.client.methods.HttpPost;

import org.apache.http.impl.client.DefaultHttpClient;

import org.apache.http.util.EntityUtils;

import org.json.JSONArray;

import org.json.JSONObject;



import android.app.Activity;

import android.os.Bundle;

import android.util.Log;

import android.widget.ListView;

import android.widget.SimpleAdapter;

import android.widget.Toast;



public class StuManagerActivity extends Activity {

	private static final String TAG = "StuManagerActivity";

	private List<HashMap<String, Object>> list = null;

	private HashMap<String, Object> stu = null;



	private ListView listView = null;

	private static String url = "http://192.168.1.103:8080/StudentServer/getJsonStu.action";



	/** Called when the activity is first created. */

	@Override

	public void onCreate(Bundle savedInstanceState) {

		super.onCreate(savedInstanceState);

		setContentView(R.layout.main);



		listView = (ListView) findViewById(R.id.stuList);

		

		getServerData(url);

	}



	public void getServerData(String url) {

		// 提供默认的HttpClient实现

		HttpClient client = new DefaultHttpClient();

		HttpPost request;



		try {

			request = new HttpPost(new URI(url));

			HttpResponse response = client.execute(request);

			// 判断请求是否成功

			if (response.getStatusLine().getStatusCode() == 200) {

				HttpEntity entity = response.getEntity();

				if (entity != null) {

					String out = EntityUtils.toString(entity, "UTF-8");

					Log.i(TAG, out);

					JSONArray jsonArray = new JSONArray(out);

					System.out.println(jsonArray.length());

					list = new ArrayList<HashMap<String, Object>>();

					System.out.println(list.size());

					

					for (int i = 0; i < jsonArray.length(); i++) {

						JSONObject jsonObject = (JSONObject) jsonArray.get(i);

						String stuName = jsonObject.getString("studentName");

						String stuSex = jsonObject.getString("stuSex");

						String phone = jsonObject.getString("phone");

						

						stu.put("stuName", stuName);

						stu.put("stuSex", stuSex);

						stu.put("phone", phone);

						

						System.out.println(stuName);

						

						list.add(stu);

						System.out.println(list.size()+"");

					}

					SimpleAdapter adapter = new SimpleAdapter(

							StuManagerActivity.this, list, R.layout.item,

							new String[] { "stuName", "stuSex", "phone" },

							new int[] { R.id.stuName, R.id.stuSex, R.id.phone });

					

					listView.setAdapter(adapter);

				}

			}

		} catch (Exception e) {

			e.printStackTrace();

			Log.e(TAG, e.toString());

			Toast.makeText(StuManagerActivity.this, "获取数据失败！", Toast.LENGTH_LONG).show();

		}



	}

}