Android httpclient、json

webservice->xml

jackson->json

从第三方项目中拿数据通常有两种方式（根据数据交互的格式来定）
xml->webservice/httpClient
json->httpClient
java java
java android
java ios
java 微信

jackson
1.1 Java->Json
1.1.1 ObjectMap
1.1.2 JsonGenerator
1.1.3 @JsonIgnore
hibernate中一对多、多对多双向关联会出现这种死循环
简介
2.1 HttpClient是Apache Jakarta Common下的子项目，用来提供高效的、最新的、
功能丰富的支持HTTP协议的客户端编程工具包，并且它支持HTTP协议最新的版本和协议。
2.2 Android已成功集成了HttpClient，这意味这开发人员可以直接在Android应用中使用
HtppClient来提交请求、接收响应

注：在API 23中，Google已经移除了移除了Apache HttpClient相关的类，
在build.gradle中的android {}中加上
useLibrary ‘org.apache.http.legacy’
详情见资料“”

httpclient的作用是在后台模拟，浏览访问后台代码的操作
案例一：HttpClient的使用步骤
HttpClient的使用步骤
3.1 创建HttpClient对象
HttpClient httpClient = new DefaultHttpClient();

3.2 创建HttpGet(或HttpPost)对象
HttpGet HttpGet = new HttpGet(“http://www.baidu.com”);
HttpPost httpPost = new HttpPost(“http://www.baidu.com”);

3.3 添加参数(可选)
setParams(HttpParams params)//HttpGet和HttpPost共有
setEntity(HttpEntity entity)//HttpPost独有

  List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("age", "20"));
params.add(new BasicNameValuePair("like", "aa"));
params.add(new BasicNameValuePair("like", "bb"));
params.add(new BasicNameValuePair("like", "cc"));
params.add(new BasicNameValuePair("newsCategoryId", "1"));
HttpEntity paramEntity = new UrlEncodedFormEntity(params,"UTF-8");
httpPost.setEntity(paramEntity);

3.4 发送GET(或POST)请求，并获得响应
HttpResponse httpResponse = httpClient.execute(HttpUriRequest request);

  注1：HttpUriRequest为HttpGet和HttpPost的父类
  注2：需要添加允许网络访问权限，不然会报错“java.lang.SecurityException: Permission denied (missing INTERNET permission?)”
       <uses-permission android:name="android.permission.INTERNET" />

  注3：如果地址错误，或服务器未开户，HttpClient这SB会等待N久(>24小时)。
       所以请记得设置超时时间，所以请记得设置超时时间，所以请记得设置超时时间
       所以请记得设置超时时间，所以请记得设置超时时间，所以请记得设置超时时间
       所以请记得设置超时时间，所以请记得设置超时时间，所以请记得设置超时时间

       另外HttpClient版本不一样，代码也不一样。下面的4.0版本的写法
       httpClient.getParams().setParameter(CoreConnectionPNames.CONNECTION_TIMEOUT, 2000);// 连接时间
       httpClient.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT, 2000);// 数据传输时间

3.5 处理响应
3.5.1 响应状态码(200)
httpResponse.getStatusLine().getStatusCode()

3.5.2 响应头
      getAllHeaders()/getHeaders(String name)

3.5.3 响应内容
      HttpEntity httpEntity = httpResponse.getEntity();//此对象包含服务器的响应内容
      String result = EntityUtils.toString(httpEntity);

//代码展示工具类
package com.example.myapplication08;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.params.CoreConnectionPNames;
import org.apache.http.util.EntityUtils;

import android.os.AsyncTask;

/**

封装 HttpClient对象POST请求

*/
public class HttpClientPost implements Serializable {

private static final long serialVersionUID = 1777547416049652217L;

private static HttpClient httpClient = new DefaultHttpClient();

static {
	httpClient.getParams().setParameter(
			CoreConnectionPNames.CONNECTION_TIMEOUT, 2000);// 连接时间
	httpClient.getParams().setParameter(CoreConnectionPNames.SO_TIMEOUT,
			3000);// 数据传输时间
}

// 字符集
private static String encoding = "UTF-8";

// 服务器地址+端口号+项目名
private static String basePath = "http://192.168.7.111:8080/web_easyUI";

// 子控制器的路径
private String path;

// 保存请求中的参数
private List<NameValuePair> params = new ArrayList<NameValuePair>();;

public HttpClientPost(String path) {
	super();
	this.path = path;
}

/**
 * 向POST请求中添加参数
 *
 * @param name
 * @param value
 */
public void addParam(String name, String value) {
	if (value == null) {
		params.add(new BasicNameValuePair(name, ""));
	} else {
		params.add(new BasicNameValuePair(name, value));
	}
}

/**
 * 提交POST请求
 */
@SuppressWarnings("unchecked")
public void submit(final HttpClientPost.Callback callback) {
	new AsyncTask() {
		private String json;

		@Override
		protected Object doInBackground(Object... args) {
			try {
				// 1. 创建HttpClient对象

				// 2. 创建HttpGet(或HttpPost)对象
				HttpPost httpPost = new HttpPost(basePath + path);

				// 3. 向POST请求中添加参数(可选)
				if (0 != params.size()) {
					HttpEntity paramEntity = new UrlEncodedFormEntity(
							params, encoding);
					httpPost.setEntity(paramEntity);
				}

				// 4. 发送POST请求，并获得响应
				HttpResponse httpResponse = httpClient.execute(httpPost);

				// 5. 处理响应
				if (200 == httpResponse.getStatusLine().getStatusCode()) {
					HttpEntity responseEntity = httpResponse.getEntity();// 此对象包含服务器的响应内容
					this.json = EntityUtils.toString(responseEntity);
				}
			} catch (Exception e) {
				throw new RuntimeException(e);
			}
			return null;
		}

		protected void onPostExecute(Object result) {
			callback.execute(this.json);
		}

	}.execute();
}

public static interface Callback {
	void execute(String json);
}

}

// 代码展示，增删改查实现类、只写了查询
package com.example.myapplication08;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.Button;

import com.fasterxml.jackson.databind.ObjectMapper;

import java.io.IOException;
import java.util.List;
import java.util.Map;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

private Button bt_main_add;
private Button bt_main_edit;
private Button bt_main_del;
private Button bt_main_load;
private Button bt_main_list;


@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    //查找控件
    findViews();

    //绑定监听器
    bt_main_add.setOnClickListener(this);
    bt_main_edit.setOnClickListener(this);
    bt_main_del.setOnClickListener(this);
    bt_main_load.setOnClickListener(this);
    bt_main_list.setOnClickListener(this);

}

private void findViews() {
    bt_main_add = (Button) findViewById(R.id.bt_main_add);
    bt_main_edit = (Button) findViewById(R.id.bt_main_edit);
    bt_main_del = (Button) findViewById(R.id.bt_main_del);
    bt_main_load = (Button) findViewById(R.id.bt_main_load);
    bt_main_list = (Button) findViewById(R.id.bt_main_list);
}


@Override
public void onClick(View v) {
    switch (v.getId()) {
        case R.id.bt_main_add:
            add();
            break;
        case R.id.bt_main_edit:
            edit();
            break;
        case R.id.bt_main_del:
            del();
            break;
        case R.id.bt_main_load:
            load();
            break;
        case R.id.bt_main_list:
            list();
            break;
    }
}

private void add() {
    Log.i("test", "add...");
}

private void edit() {
    Log.i("test", "edit...");
}

private void del() {
    Log.i("test", "del...");
}

private void load() {
    Log.i("test", "load...");
}

private void list() {
            Log.i("test", "list...");
            HttpClientPost clientPost = new HttpClientPost("/userAction.action");
            clientPost.addParam("methodName","listUser");
            clientPost.submit(new HttpClientPost.Callback() {
                @Override
                public void execute(String json) {
                    Log.i("json",json);
                    ObjectMapper om = new ObjectMapper();
                    try {
                        Map map = om.readValue(json, Map.class);
                        List rows = (List) map.get("rows");
                        Map<String,String> o = (Map<String, String>) rows.get(0);
                        Log.i("uname",o.get("uname"));

                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            });
}

}
// 代码展示 xml框

<?xml version="1.0" encoding="utf-8"?>

<Button
    android:id="@+id/bt_main_add"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="新增" />

<Button
    android:id="@+id/bt_main_edit"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="修改" />

<Button
    android:id="@+id/bt_main_del"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="删除" />

<Button
    android:id="@+id/bt_main_load"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="查单个" />

<Button
    android:id="@+id/bt_main_list"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="查全部" />

案例二：使用HttpClientUtils与服务器通信
4. Android客户端与服务器通信
4.1 JSON数据交换
android系统内置了对象json的支持，另外json其实就以下几个对象的使用：
JSONObject、JSONArray、JSONStringer、JSONException
4.2 web service，底层使用xml交换数据

关于org.apache.http.conn.HttpHostConnectException: Connection to refused错误的解决办法
增加网络访问权限：
找到 AndroidManifest.xml 文件。在application标签后面加上
检查ip地址：
启动的android模拟器吧自己也当成127.0.0.1和localhost，如果使用了localhost或者127.0.0.1则会被拒绝访问，
把ip地址改成实际地址，如：192.168.1.5

Android httpclient、json

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