1 HttpClient简介
在JDK中java.net包下提供了用户HTTP访问的基本功能,但是它缺少灵活性或许多应用所需要的功能。
HttpClient起初是Apache Jakarta Common 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。2007年成为顶级项目。
通俗解释:HttpClient可以实现使用Java代码完成标准HTTP请求及响应。
2 代码实现
2.1 服务端
新建项目HttpClientServer
2.1.1 新建控制器
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com.mrshun.controller.DemoController @Controller public class DemoController { @RequestMapping ( "/demo" ) @ResponseBody public String demo(String param){ return "demo" +param; } } |
2.1.2 新建启动器
新建启动器
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com.mrshun.HttpClientServerApplication @SpringBootApplication public class HttpClientServerApplication { public static void main(String[] args) { SpringApplication.run(HttpClientServerApplication. class ,args); } } |
2.2 客户端
新建HttpClientDemo项目
2.2.1 添加依赖
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< dependencies > < dependency > < groupId >org.apache.httpcomponents</ groupId > < artifactId >httpclient</ artifactId > < version >4.5.10</ version > </ dependency > </ dependencies > |
2.2.2 新建类
新建com.mrshun.HttpClientDemo,编写主方法。
2.2.2.1 使用GET方法访问
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public static void main(String[] args) { try { //创建http工具(理解成:浏览器) 发起请求,解析响应 CloseableHttpClient httpClient = HttpClients.createDefault(); //请求路径 URIBuilder uriBuilder = new URIBuilder( "http://localhost:8080/demo" ); uriBuilder.addParameter( "param" , "get123" ); //创建HttpGet请求对象 HttpGet get = new HttpGet(uriBuilder.build()); //创建响应对象 CloseableHttpResponse response = httpClient.execute(get); //由于响应体是字符串,因此把HttpEntity类型转换为字符串类型,并设置字符编码 String result = EntityUtils.toString(response.getEntity(), "utf-8" ); //输出结果 System.out.println(result); //释放资源 response.close(); httpClient.close(); } catch (URISyntaxException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } } |
2.2.2.2 使用POST方式访问
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public class HttpClientDemo { public static void main(String[] args) { try { //创建http工具(理解成:浏览器) 发起请求,解析响应 CloseableHttpClient httpClient = HttpClients.createDefault(); //创建HttpPOST请求对象 HttpPost post = new HttpPost( "http://localhost:8080/demo" ); //所有请求参数 List<NameValuePair> params = new ArrayList<>(); params.add( new BasicNameValuePair( "param" , "123" )); //创建HttpEntity接口的文本实现类的对象,放入参数并设置编码 HttpEntity httpEntity = new UrlEncodedFormEntity(params, "utf-8" ); //放入到HttpPost对象中 post.setEntity(httpEntity); //创建响应对象 CloseableHttpResponse response = httpClient.execute(post); //由于响应体是字符串,因此把HttpEntity类型转换为字符串类型 String result = EntityUtils.toString(response.getEntity()); //输出结果 System.out.println(result); //释放资源 response.close(); httpClient.close(); } catch (IOException e) { e.printStackTrace(); } } } |
3. Jackson用法
3.1 把对象转换为json字符串
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ObjectMapper objectMapper = new ObjectMapper(); People peo = new People(); objectMapper.writeValueAsString(peo); |
3.2 把json字符串转换为对象
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ObjectMapper objectMapper = new ObjectMapper(); People peo = objectMapper.readValue(content, People. class ); |
3.3 把json字符串转换为List集合
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ObjectMapper objectMapper = new ObjectMapper(); JavaType javaType = objectMapper.getTypeFactory().constructParametricType(List. class , People. class ); List<People> list = objectMapper.readValue(content, javaType); |
4 HttpClient请求包含JSON
4.1 java代码实现
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public class HttpClientDemo { public static void main(String[] args) { try { CloseableHttpClient httpClient = HttpClients.createDefault(); HttpPost post = new HttpPost( "http://localhost:8080/demo" ); HttpEntity httpEntity= null ; String json = "{}" ; StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON); post.setEntity(entity); CloseableHttpResponse response = httpClient.execute(post); String result = EntityUtils.toString(response.getEntity()); System.out.println(result); response.close(); httpClient.close(); } catch (IOException e) { e.printStackTrace(); } } } |
5 控制器接口参数
@RequestBody把请求体中流数据转换为指定的对象。多用在请求参数是json数据且请求的Content-Type=”application/json”
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@RequestMapping ( "/demo4" ) @ResponseBody public String demo4( @RequestBody List<People> list) { System.out.println(list); return list.toString(); } |
6 Ajax发送json参数写法
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var json = '[{"id":123,"name":"mrshun"},{"id":123,"name":"zhangyongshun"}]' ; $.ajax({ url: '/demo5' , type: 'post' , success: function (data){ alert(data); for ( var i = 0 ;i<data.length;i++){ alert(data[i].id + " " +data[i].name); } }, contentType: 'application/json' , //请求体中内容类型 dataType: 'json' , //响应内容类型。 data:json }); |
7 跨域
- 跨域:协议、ip、端口中只要有一个不同就是跨域请求。
- 同源策略:浏览器默认只允许ajax访问同源(协议、ip、端口都相同)内容。
解决同源策略:
在控制器接口上添加@CrossOrigin。表示允许跨域。本质在响应头中添加Access-Control-Allow-Origin: *
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var json = '[{"id":123,"name":"mrshun"},{"id":456,"name":"zhangyongshun"}]' ; $.ajax({ url: '/demo5' , type: 'post' , success: function (data){ alert(data); for ( var i = 0 ;i<data.length;i++){ alert(data[i].id + " " +data[i].name); } }, contentType: 'application/json' , //请求体中内容类型 dataType: 'json' , //响应内容类型。 data:json }); |
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原文链接:https://blog.csdn.net/qq_46144237/article/details/120751147