spring学习之restTemplate常用方法介绍

柔情只为你懂 2022-01-28 07:17 205阅读 0赞

### restTemplate学习 ###

*  什么是RestTemplate
 *  常用方法
 *   *  getForObject
     *  getForEntity
     *  headForHeaders
     *  postForLocation
     *  postForObject
     *  postForEntity
     *  put
     *  patchForObject
     *  delete
     *  optionsForAllow
     *  exchange
     *  例子源码地址

# 什么是RestTemplate #

*  RestTemplate用于同步client端的核心类，简化了与http服务的通信，并满足RestFul原则，程序代码可以给它提供URL，并提取结果
 *  默认情况下，RestTemplate默认使用jdk提供http链接的能力（HttpURLConnection）
 *  可以通过setRequestFactory属性切换到不同的HTTP源，Apache HttpComponents,Netty和OkHttp。

# 常用方法 #

> restTemplate其他的先不讲，直接上来操作，熟个手

## getForObject ##

> getForObject函数实际上是对getForEntity函数的进一步封装，如果你只关注返回的消息体的内容，对其他信息都不关注，此时可以使用getForObject

1.  **public T getForObject(String url, Class responseType, Object… uriVariables)**
    
        String oneGet = restTemplate.getForObject("http://localhost:6788/oneGet", String.class);
        System.out.println(oneGet);
        //可以用一个数字做占位符，最后是一个可变长度的参数，来一一替换前面的占位符
        String oneGet1 = restTemplate.getForObject("http://localhost:6788/oneGet/{1}", String.class,"1");
        System.out.println(oneGet1);
2.  **public T getForObject(String url, Class responseType, Map<String, ?> uriVariables)**
    
        //也可以前面使用id={id}这种形式，最后一个参数是一个map，map的key即为前边占位符的名字，map的value为参数值
        HashMap<String, Object> twoGetMap = new HashMap<>();
        twoGetMap.put("id","1");
        String twoGet = restTemplate.getForObject("http://localhost:6788/twoGet?id={id}", String.class,twoGetMap);
        System.out.println(twoGet);
3.  **public T getForObject(URI url, Class responseType)**
    
        String threeGet = restTemplate.getForObject(new URI("http://localhost:6788/threeGet"), String.class);
        System.out.println(threeGet);
    
        ====================getForObject=======================
        { "code":1,"message":"","data":"oneGet"}
        { "code":1,"message":"","data":"oneGet1--1"}
        { "code":1,"message":"","data":"twoGet--1"}
        { "code":1,"message":"","data":"threeGet"}

## getForEntity ##

> getForEntity方法的返回值是一个ResponseEntity，ResponseEntity是Spring对HTTP请求响应的封装，包括了几个重要的元素，如响应码、contentType、contentLength、响应消息体等

1.  **public ResponseEntity getForEntity(String url, Class responseType, Object… uriVariables)**
    
        ResponseEntity<String> oneGetEntity = restTemplate.getForEntity("http://localhost:6788/oneGet", String.class);
        System.out.println(oneGetEntity);
        ResponseEntity<String> oneGetEntity1 = restTemplate.getForEntity("http://localhost:6788/oneGet/{1}", String.class, "1");
        System.out.println(oneGetEntity1);
2.  **public ResponseEntity getForEntity(String url, Class responseType, Map<String, ?> uriVariables)**
    
        //也可以前面使用id={id}这种形式，最后一个参数是一个map，map的key即为前边占位符的名字，map的value为参数值
        HashMap<String, Object> twoGetMapEntity = new HashMap<>();
        twoGetMapEntity.put("id","1");
        ResponseEntity<String> twoGetEntity = restTemplate.getForEntity("http://localhost:6788/twoGet?id={id}", String.class,twoGetMapEntity);
        System.out.println(twoGetEntity);
3.  **public ResponseEntity getForEntity(URI url, Class responseType)**
    
        ResponseEntity<String> threeGetEntity = restTemplate.getForEntity(new URI("http://localhost:6788/threeGet"), String.class);
        System.out.println(threeGetEntity);
    
        ====================getForEntity=======================
        <200,{ "code":1,"message":"","data":"oneGet"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Fri, 24 May 2019 01:09:43 GMT"]>
        <200,{ "code":1,"message":"","data":"oneGet1--1"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Fri, 24 May 2019 01:09:43 GMT"]>
        <200,{ "code":1,"message":"","data":"twoGet--1"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Fri, 24 May 2019 01:09:43 GMT"]>
        <200,{ "code":1,"message":"","data":"threeGet"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Fri, 24 May 2019 01:09:43 GMT"]>

## headForHeaders ##

> 获取请求头，用于检查对象是否存在，不返回body信息

1.  **public HttpHeaders headForHeaders(String url, Object… uriVariables)**
    
        HttpHeaders oneHeaders = restTemplate.headForHeaders("http://localhost:6788/oneGet");
        System.out.println(oneHeaders);
2.  **public HttpHeaders headForHeaders(String url, Map<String, ?> uriVariables)**
    
        HashMap<String, Object> headMap = new HashMap<>();
        headMap.put("id","1");
        HttpHeaders twoHeaders = restTemplate.headForHeaders("http://localhost:6788/twoGet?id={id}", headMap);
        System.out.println(twoHeaders);
3.  **public HttpHeaders headForHeaders(URI url)**
    
        HttpHeaders threeHeaders = restTemplate.headForHeaders(new URI("http://localhost:6788/oneGet"));
        System.out.println(threeHeaders);
    
        ====================headForHeaders=======================
        [Content-Type:"application/json;charset=UTF-8", Content-Length:"39", Date:"Fri, 24 May 2019 02:05:03 GMT"]
        [Content-Type:"application/json;charset=UTF-8", Content-Length:"42", Date:"Fri, 24 May 2019 02:05:03 GMT"]
        [Content-Type:"application/json;charset=UTF-8", Content-Length:"39", Date:"Fri, 24 May 2019 02:05:03 GMT"]

## postForLocation ##

> post提交，获取重定向的url,该Uri表示新资源的位置

1.  **public URI postForLocation(String url, @Nullable Object request, Object… uriVariables)**
    
        HttpEntity<Object> entity = new HttpEntity<>(null,null);//第一个参数为body参数，第二个参数为headers（请求头）
        URI oneUri = restTemplate.postForLocation("http://localhost:6788/onePost",entity);
        System.out.println(oneUri);
        URI oneUri1 = restTemplate.postForLocation("http://localhost:6788/onePost?id={id}",entity,"---1");
        System.out.println(oneUri1);
2.  **public URI postForLocation(String url, @Nullable Object request, Map<String, ?> uriVariables)**
    
        HttpEntity<Object> entity = new HttpEntity<>(null,null);
        HashMap<String, Object> uriMap = new HashMap<>();
        uriMap.put("id","---1");
        URI twoUri = restTemplate.postForLocation("http://localhost:6788/onePost?id={id}", entity, uriMap);
        System.out.println(twoUri);
3.  **public URI postForLocation(URI url, @Nullable Object request)**
    
        URI threeUri = restTemplate.postForLocation(new URI("http://localhost:6788/onePost"), entity);
        System.out.println(threeUri);
    
        ====================postForLocation=======================
        https://blog.csdn.net/YCJ_xiyang/column/info/38209
        https://blog.csdn.net/YCJ_xiyang/column/info/38209---1
        https://blog.csdn.net/YCJ_xiyang/column/info/38209---1
        https://blog.csdn.net/YCJ_xiyang/column/info/38209

## postForObject ##

1.  **public T postForObject(String url, @Nullable Object request, Class responseType,  
    Object… uriVariables)**
    
        HttpHeaders headers = new HttpHeaders();
        headers.add("Content-Type", MediaType.APPLICATION_JSON_VALUE);
        Gson gson = new Gson();
        Map<String,String> postMaps = new HashMap<>();
        postMaps.put("name","cat");
        HttpEntity<Object> postEntity = new HttpEntity<>(gson.toJson(postMaps),headers);
        String onePost = restTemplate.postForObject("http://localhost:6788/onePost",postEntity,String.class);
        System.out.println(onePost);
        String onePost1 = restTemplate.postForObject("http://localhost:6788/onePost?id={id}",postEntity,String.class,"---1");
        System.out.println(onePost1);
2.  **public T postForObject(String url, @Nullable Object request, Class responseType,  
    Map<String, ?> uriVariables)**
    
        HttpHeaders headers = new HttpHeaders();
        headers.add("Content-Type", MediaType.APPLICATION_JSON_VALUE);
        Gson gson = new Gson();
        Map<String,String> postMaps = new HashMap<>();
        postMaps.put("name","cat");
        HttpEntity<Object> postEntity = new HttpEntity<>(gson.toJson(postMaps),headers);
        HashMap<String, Object> postMap = new HashMap<>();
        postMap.put("id","---1");
        String twoPost = restTemplate.postForObject("http://localhost:6788/onePost?id={id}", postEntity,String.class, postMap);
        System.out.println(twoPost);
3.  **public T postForObject(URI url, @Nullable Object request, Class responseType)**
    
        HttpHeaders headers = new HttpHeaders();
        headers.add("Content-Type", MediaType.APPLICATION_JSON_VALUE);
        Gson gson = new Gson();
        Map<String,String> postMaps = new HashMap<>();
        postMaps.put("name","cat");
        HttpEntity<Object> postEntity = new HttpEntity<>(gson.toJson(postMaps),headers);
        String threePost = restTemplate.postForObject(new URI("http://localhost:6788/onePost"), postEntity,String.class);
        System.out.println(threePost);
    
        ====================postForObject=======================
        { "code":1,"message":"","data":"onePostnull----{\"name\":\"cat\"}"}
        { "code":1,"message":"","data":"onePost---1----{\"name\":\"cat\"}"}
        { "code":1,"message":"","data":"onePost---1----{\"name\":\"cat\"}"}
        { "code":1,"message":"","data":"onePostnull----{\"name\":\"cat\"}"}

## postForEntity ##

1.  **public ResponseEntity postForEntity(String url, @Nullable Object request,  
    Class responseType, Object… uriVariables)**
    
        HttpHeaders postHeadersEntity = new HttpHeaders();
        postHeadersEntity.add("Content-Type", MediaType.APPLICATION_FORM_URLENCODED_VALUE);
        MultiValueMap<String,String> body = new LinkedMultiValueMap<>();
        body.add("name","tom");
        HttpEntity<Object> postEntitys = new HttpEntity<>(body,postHeadersEntity);
        ResponseEntity<String> onePostEntity = restTemplate.postForEntity("http://localhost:6788/onePostEntity", postEntitys, String.class);
        System.out.println(onePostEntity);
        ResponseEntity<String> onePostEntity1 = restTemplate.postForEntity("http://localhost:6788/onePostEntity?id={id}",postEntitys,String.class,"---1");
        System.out.println(onePostEntity1);
2.  **public ResponseEntity postForEntity(String url, @Nullable Object request,  
    Class responseType, Map<String, ?> uriVariables)**
    
        HttpHeaders postHeadersEntity = new HttpHeaders();
        postHeadersEntity.add("Content-Type", MediaType.APPLICATION_FORM_URLENCODED_VALUE);
        MultiValueMap<String,String> body = new LinkedMultiValueMap<>();
        body.add("name","tom");
        HttpEntity<Object> postEntitys = new HttpEntity<>(body,postHeadersEntity);
        HashMap<String, Object> postMapEntity = new HashMap<>();
        postMapEntity.put("id","---1");
        ResponseEntity<String> twoPostEntity = restTemplate.postForEntity("http://localhost:6788/onePostEntity?id={id}", postEntitys,String.class, postMapEntity);
        System.out.println(twoPostEntity);
3.  **public ResponseEntity postForEntity(URI url, @Nullable Object request, Class responseType)**
    
        HttpHeaders postHeadersEntity = new HttpHeaders();
        postHeadersEntity.add("Content-Type", MediaType.APPLICATION_FORM_URLENCODED_VALUE);
        MultiValueMap<String,String> body = new LinkedMultiValueMap<>();
        body.add("name","tom");
        HttpEntity<Object> postEntitys = new HttpEntity<>(body,postHeadersEntity);
        HashMap<String, Object> postMapEntity = new HashMap<>();
        postMapEntity.put("id","---1");
        ResponseEntity<String> threePostEntity = restTemplate.postForEntity(new URI("http://localhost:6788/onePostEntity"), postEntitys,String.class);
        System.out.println(threePostEntity);
    
    > 扩展content-type:form-data
    > 
    >     HttpHeaders postHeadersEntitys = new HttpHeaders();
    >      postHeadersEntity.add("Content-Type", MediaType.MULTIPART_FORM_DATA_VALUE);
    >      MultiValueMap<String,String> bodys = new LinkedMultiValueMap<>();
    >      bodys.add("name","sam");
    >      HttpEntity<Object> postEntityss = new HttpEntity<>(bodys,postHeadersEntitys);
    >      ResponseEntity<String> onePostEntitys = restTemplate.postForEntity("http://localhost:6788/onePostEntity", postEntityss, String.class);
    >      System.out.println(onePostEntitys);
    
        ====================postForEntity=======================
        <200,{ "code":1,"message":"","data":"onePostEntitynull----tom"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 01:20:58 GMT"]>
        <200,{ "code":1,"message":"","data":"onePostEntity---1----tom"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 01:20:58 GMT"]>
        <200,{ "code":1,"message":"","data":"onePostEntity---1----tom"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 01:20:58 GMT"]>
        <200,{ "code":1,"message":"","data":"onePostEntitynull----tom"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 01:20:58 GMT"]>
        ====================postForEntity扩展=======================
        <200,{ "code":1,"message":"","data":"onePostEntitynull----sam"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 01:20:58 GMT"]>

## put ##

> put 在restful中 表示更新或创建，清楚参数和post差不多，只不过没有返回值，这里只演示一种

1.  **public void put(String url, @Nullable Object request, Object… uriVariables)**
    
        HttpHeaders putHeaders = new HttpHeaders();
        putHeaders.add("Content-Type", MediaType.APPLICATION_JSON_VALUE);
        HttpEntity<Object> putEntity = new HttpEntity<>(null,putHeaders);
        restTemplate.put("http://localhost:6788/put?id={id}",putEntity,"--1");
2.  **public void put(String url, @Nullable Object request, Map<String, ?> uriVariables)**
3.  **public void put(URI url, @Nullable Object request)**

## patchForObject ##

> patch接口表示修改,参数和上面的类似，不一一演示了  
> 注意：restTemplate默认使用的jdk的HttpURLConnection，不支持patch，需要替换为Apache HttpComponents  
> 引入依赖`compile group: 'org.apache.httpcomponents', name: 'httpclient', version: '4.5.2'`
> 
>     restTemplate.setRequestFactory(new HttpComponentsClientHttpRequestFactory());

1.  **public T patchForObject(String url, @Nullable Object request, Class responseType,  
    Object… uriVariables)**
    
        HttpHeaders patchHeaders = new HttpHeaders();
        patchHeaders.add("Content-Type", MediaType.APPLICATION_JSON_VALUE);
        HttpEntity<Object> patchEntity = new HttpEntity<>(null,patchHeaders);
        String patch = restTemplate.patchForObject("http://localhost:6788/patch?id={id}", patchEntity, String.class, "--1");
        System.out.println(patch);
2.  **public T patchForObject(String url, @Nullable Object request, Class responseType,  
    Map<String, ?> uriVariables)**
3.  **public T patchForObject(URI url, @Nullable Object request, Class responseType)**
    
        ====================patchForObject=======================
        { "code":1,"message":"","data":"patch----1"}

## delete ##

> 顾名思义：表示删除的接口,无返回值

1.  **public void delete(String url, Object… uriVariables)**
    
        restTemplate.delete("http://localhost:6788/delete?id={id}",  "--1");
2.  **public void delete(String url, Map<String, ?> uriVariables)**
3.  **public void delete(URI url)**
    
        ====================delete=======================
        [GET, HEAD, POST, PUT, PATCH, DELETE, OPTIONS]

## optionsForAllow ##

> 询问可以执行哪些方法，参数跟上面类似，演示一种

1.  **public Set optionsForAllow(String url, Object… uriVariables)**
    
        Set<HttpMethod> httpMethods = restTemplate.optionsForAllow("http://localhost:6788/optionsForAllow?id={id}", "--1");
         System.out.println(httpMethods);
2.  **public Set optionsForAllow(String url, Map<String, ?> uriVariables)**
3.  **public Set optionsForAllow(URI url)**
    
        ====================optionsForAllow=======================
        [GET, HEAD, POST, PUT, PATCH, DELETE, OPTIONS]

## exchange ##

> exchange方法提供统一的方法模板进行四种请求：POST,PUT,DELETE,GET  
> 说明：  
> 1）url: 请求地址；  
> 2）method: 请求类型(如：POST,PUT,DELETE,GET)；  
> 3）requestEntity: 请求实体，封装请求头，请求内容  
> 4）responseType: 响应类型，根据服务接口的返回类型决定  
> 5）uriVariables: url中参数变量值

1.  **public ResponseEntity exchange(String url, HttpMethod method,@Nullable HttpEntity<?> requestEntity,  
    Class responseType, Object… uriVariables)**
2.  **public ResponseEntity exchange(String url, HttpMethod method,@Nullable HttpEntity<?> requestEntity,  
    Class responseType ,Map<String, ?> uriVariables )**
3.  **public ResponseEntity exchange(URI url, HttpMethod method, @Nullable HttpEntity<?> requestEntity,  
    Class responseType)**

> 前面3种，参数类似，和上面的操作相同

1.  **public ResponseEntity exchange(String url, HttpMethod method, @Nullable HttpEntity<?> requestEntity,  
    ParameterizedTypeReference responseType, Object… uriVariables)**
2.  **public ResponseEntity exchange(String url, HttpMethod method, @Nullable HttpEntity<?> requestEntity,  
    ParameterizedTypeReference responseType, Map<String, ?> uriVariables)**
3.  **public ResponseEntity exchange(URI url, HttpMethod method, @Nullable HttpEntity<?> requestEntity,  
    ParameterizedTypeReference responseType)**
4.  **public ResponseEntity exchange(RequestEntity<?> requestEntity, ParameterizedTypeReference responseType)**

> 上面4种，ParameterizedTypeReference 支持即泛型类作为返回类型  
> 例子：[ParameterizedTypeReference 例子][ParameterizedTypeReference]

1.  **public ResponseEntity exchange(RequestEntity<?> requestEntity, Class responseType)**
    
    > 最后一种RequestEntity<?>里面加请求头，请求方法，请求地址
    
        //get添加请求头
        HttpHeaders exchangeHeaders = new HttpHeaders();
        exchangeHeaders.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
        URI url = new URI("http://localhost:6788/exchange?id=--1");
        RequestEntity<Object> orderEntity = new RequestEntity<>(exchangeHeaders,HttpMethod.GET,url);
        ResponseEntity<String> result = restTemplate.exchange(orderEntity, String.class);
        System.out.println(result);
        ====================exchange=======================
        <200,{ "code":1,"message":"","data":"exchange--1"},[Content-Type:"application/json;charset=UTF-8", Transfer-Encoding:"chunked", Date:"Tue, 28 May 2019 02:45:26 GMT"]>

## 例子源码地址 ##

[例子源码地址][Link 1]

[ParameterizedTypeReference]: https://blog.csdn.net/herojuice/article/details/86132183
[Link 1]: https://m.gitee.com/xiyang_ycj/spring-restTemplate#0-sqq-1-50307-9737f6f9e09dfaf5d3fd14d775bfee85