使用Spring RestTemplate 詳解實踐使用及拓展增強

更新時間：2021年10月28日 10:28:54 作者：isyoungboy

這篇文章主要介紹了使用Spring RestTemplate 詳解實踐使用及拓展增強，具有很好的參考價值，希望對大家有所幫助。如有錯誤或未考慮完全的地方，望不吝賜教

RestTemplate 是什么？

RestTemplate 是Spring封裝的一個Rest風(fēng)格http請求框架，底層可以切換成HttpClient OkHttp 或者Netty實現(xiàn)，用戶只需要關(guān)心RestTemplate怎么用而不需要關(guān)心底層框架如何操作，使用RestTemplate不需要關(guān)心如何手動轉(zhuǎn)換返回的對象和到處都是的異常處理代碼，可以讓你的代碼更簡潔更優(yōu)雅。

你可以在 spring-web 中找到它

主要類和接口

RestOperations 定義Rest 操作的接口
HttpAccessor 抽象http help 類
InterceptingHttpAccessor HttpAccess 裝飾類拓展了攔截器功能
RestTemplate 具體實現(xiàn)類
ClientHttpRequestInterceptor 攔截器接口用于攔截http請求
UriTemplateHandler uri模板處理器，后面拓展會用到

uml圖

基礎(chǔ)使用

put delete 等方法參考get post 的寫法

Get獲取對象或?qū)ο蠹?/h3>

獲取 Employee 集合

RestTemplate restTemplate = new RestTemplate();
ResponseEntity<List<Employee>> response = restTemplate.exchange(
  "http://localhost:8080/employees/",
  HttpMethod.GET,
  null,
  new ParameterizedTypeReference<List<Employee>>(){});
List<Employee> employees = response.getBody();

返回對象list用exchange方法使用 ParameterizedTypeReference 指定返回類型，getForEntity 也可以使用 Object[].class 或其他數(shù)組接收再轉(zhuǎn)為List

獲取單個對象

public class EmployeeList {
    private List<Employee> employees;
 
    public EmployeeList() {
        employees = new ArrayList<>();
    }
 
    // getter/setter
}
EmployeeList response = restTemplate.getForObject(
  "http://localhost:8080/employees",
  EmployeeList.class);
List<Employee> employees = response.getEmployees();

Post 發(fā)送對象或集合

發(fā)送集合

List<Employee> newEmployees = new ArrayList<>();
newEmployees.add(new Employee(3, "Intern"));
newEmployees.add(new Employee(4, "CEO"));
 
restTemplate.postForObject(
  "http://localhost:8080/employees/",
  newEmployees,
  ResponseEntity.class);

發(fā)送對象

List<Employee> newEmployees = new ArrayList<>();
newEmployees.add(new Employee(3, "Intern"));
newEmployees.add(new Employee(4, "CEO"));
 
restTemplate.postForObject(
  "http://localhost:8080/employees",
  new EmployeeList(newEmployees),
  ResponseEntity.class);

上傳文件

public void uploadFile(){
    HttpHeaders headers = new HttpHeaders();
    //設(shè)置Content-Type
    headers.setContentType(MediaType.MULTIPART_FORM_DATA);
    MultiValueMap<String, Object> body
      = new LinkedMultiValueMap<>();
    body.add("file", getTestFile());
    HttpEntity<MultiValueMap<String, Object>> requestEntity
     = new HttpEntity<>(body, headers);
     
    String serverUrl = "http://localhost:8082/spring-rest/fileserver/singlefileupload/";
     
    RestTemplate restTemplate = new RestTemplate();
    ResponseEntity<String> response = restTemplate
      .postForEntity(serverUrl, requestEntity, String.class);
}
public FileSystemResource getTestFile(){
    return new FileSystemResource("./test.md")
}

FileSystemResource 是spring中的一個類參考

上傳多個文件

在上傳單個文件的基礎(chǔ)上多加幾個文件

MultiValueMap<String, Object> body
  = new LinkedMultiValueMap<>();
body.add("files", getTestFile());
body.add("files", getTestFile());
body.add("files", getTestFile());
     
HttpEntity<MultiValueMap<String, Object>> requestEntity
  = new HttpEntity<>(body, headers);
 
String serverUrl = "http://localhost:8082/spring-rest/fileserver/multiplefileupload/";
 
RestTemplate restTemplate = new RestTemplate();
ResponseEntity<String> response = restTemplate
  .postForEntity(serverUrl, requestEntity, String.class);

Spring RestTemplate 拓展

解決restTemplate get* url參數(shù)必須寫死的問題
解決get*方法不好添加header信息的問題

繼承RestTemplate 拓展get方法

/**
* 繼承RestTemplate 新加get* 方法 比原有的方法多了個 httpHeaders 參數(shù)
*/
public class CustomerRestTemplate extends RestTemplate {
    public <T> ResponseEntity<T> getForEntity(String url, HttpHeaders httpHeaders, Class<T> responseType, Object... uriVariables) throws RestClientException {
        HttpEntity<Object> requestEntity = new HttpEntity<>(httpHeaders);
        RequestCallback requestCallback = httpEntityCallback(requestEntity, responseType);
        ResponseExtractor<ResponseEntity<T>> responseExtractor = responseEntityExtractor(responseType);
        return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
    }
    public <T> ResponseEntity<T> getForEntity(String url, HttpHeaders httpHeaders, Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException {
        HttpEntity<Object> requestEntity = new HttpEntity<>(httpHeaders);
        RequestCallback requestCallback = httpEntityCallback(requestEntity, responseType);
        ResponseExtractor<ResponseEntity<T>> responseExtractor = responseEntityExtractor(responseType);
        return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
    }
    public <T> T getForObject(String url, HttpHeaders httpHeaders, Class<T> responseType, Map<String, ?> uriVariables) throws RestClientException {
        HttpEntity<Object> requestEntity = new HttpEntity<>(httpHeaders);
        RequestCallback requestCallback = httpEntityCallback(requestEntity, responseType);
        ResponseExtractor<T> responseExtractor = new HttpMessageConverterExtractor<T>(responseType, getMessageConverters());
        return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
    }
    public <T> T getForObject(String url, HttpHeaders httpHeaders, Class<T> responseType, Object... uriVariables) throws RestClientException {
        HttpEntity<Object> requestEntity = new HttpEntity<>(httpHeaders);
        RequestCallback requestCallback = httpEntityCallback(requestEntity, responseType);
        ResponseExtractor<T> responseExtractor = new HttpMessageConverterExtractor<T>(responseType, getMessageConverters());
        return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);
    }
}

拓展URI處理邏輯

/**
* 根據(jù)uriTemplate 把 uriVariables 分成兩類 
* 一類是path params 一類是 query params 分開賦值
* 如 /xx/{id}/type  path params 就是 id uriVariables 剩下的就是query params 用？拼接在url后面
* 如果查詢參數(shù)中有數(shù)組或集合類型的參數(shù)會轉(zhuǎn)化成 key[]=value1&key[]=value2...
*/
public class QueryParamsUrlTemplateHandler extends DefaultUriTemplateHandler {
    /**
     * 匹配path param
     */
    private static final Pattern NAMES_PATTERN = Pattern.compile("\\{([^/]+?)\\}");
    @Override
    public URI expand(String uriTemplate, Map<String, ?> uriVariables) {
        UriComponentsBuilder uriComponentsBuilder = UriComponentsBuilder.fromHttpUrl(uriTemplate);
        //解析uriTemplate 提取query param
        Map<String, ?> queryParam = getQueryParam(uriTemplate, uriVariables);
        //設(shè)置query param
        queryParam.forEach((k, v) -> {
            if (v instanceof Object[]) {
                Object[] arrayParam = (Object[]) v;
                //把數(shù)組類型的參數(shù)拼成 參數(shù)名 + [] 的形式 k[]  xx&kp[]=xx&k[]=xx
                String key = k + "[]";
                String strArrayParam = Stream.of(arrayParam).map(String::valueOf).collect(Collectors.joining("&" + key + "="));
                uriComponentsBuilder.queryParam(key, strArrayParam);
            } else if (v instanceof Iterable) {
                Iterable iterable = (Iterable) v;
                String key = k + "[]";
                String strArrayParam = Stream.of(iterable).map(String::valueOf).collect(Collectors.joining("&" + key + "="));
                uriComponentsBuilder.queryParam(key, strArrayParam);
            } else {
                uriComponentsBuilder.queryParam(k, v);
            }
        });
        uriTemplate = uriComponentsBuilder.build().toUriString();
        //設(shè)置path param
        return super.expand(uriTemplate, uriVariables);
    }
    /**
     * 解析uriTemplate 分離 query param
     *
     * @param uriTemplate  uri模板
     * @param uriVariables 全部的模板變量
     * @return 查詢變量
     */
    public Map<String, ?> getQueryParam(String uriTemplate, Map<String, ?> uriVariables) {
        if (uriTemplate == null) {
            return null;
        }
        if (uriTemplate.indexOf('{') == -1) {
            return uriVariables;
        }
        if (uriTemplate.indexOf(':') != -1) {
            uriTemplate = sanitizeSource(uriTemplate);
        }
        Map<String, Object> pathVariables = Maps.newHashMap();
        Matcher matcher = NAMES_PATTERN.matcher(uriTemplate);
        while (matcher.find()) {
            String matchKey = matcher.group(1);
            Object value = uriVariables.get(matchKey);
            if (value != null) {
                pathVariables.put(matchKey, value);
            }
        }
        //此處為了圖方便使用了 guava 工具包中的類 功能就是取差集
        MapDifference<String, Object> difference = Maps.difference(uriVariables, pathVariables);
        return difference.entriesOnlyOnLeft();
    }
    /**
     * Remove nested "{}" such as in URI vars with regular expressions.
     */
    private static String sanitizeSource(String source) {
        int level = 0;
        StringBuilder sb = new StringBuilder();
        for (char c : source.toCharArray()) {
            if (c == '{') {
                level++;
            }
            if (c == '}') {
                level--;
            }
            if (level > 1 || (level == 1 && c == '}')) {
                continue;
            }
            sb.append(c);
        }
        return sb.toString();
    }
}

實際使用

初始化RestTemplate

SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();
requestFactory.setConnectTimeout(500);// 設(shè)置超時
requestFactory.setReadTimeout(500);
//new 自己定義的類
CustomerRestTemplate restTemplate = new CustomerRestTemplate();
//設(shè)置自定義的uri處理處理器
QueryParamsUrlTemplateHandler queryParamsUrlTemplateHandler = new QueryParamsUrlTemplateHandler();
//這里使用裝飾模式 添加rootUri
RootUriTemplateHandler rootUriTemplateHandler = new RootUriTemplateHandler(outUrl, queryParamsUrlTemplateHandler);
restTemplate.setUriTemplateHandler(rootUriTemplateHandler);
restTemplate.setRequestFactory(requestFactory);

get請求示例

Map<String, Object> params = new HashMap<>();
params.put("id", "1");
params.put("param2", "2");
params.put("param", new Integer[]{1506, 1507});
HttpHeaders httpHeaders = new HttpHeaders();
httpHeaders.add("Authorization", "Basic " + "your authorization");
ResponseEntity<Map[]> forEntity = restTemplate.getForEntity("/api/test/{id}", httpHeaders, Map[].class, params);
// url 為 api/test/1?param[]=1506&param[]=1507&param2=2

思考進一步封裝

可以考慮使用建造者模式改造restTemplate

Employee employee = RestTemplate.build()
            .get("api/xxx/{id}")
            .header("xx","xx")
            .headers(new Headers())
            .param("xx","xx")
            .params(new HashMap(){{put("bb","bb");}})
            .targetClass(Employee.class)
            .execute();

以上為個人經(jīng)驗，希望能給大家一個參考，也希望大家多多支持腳本之家。

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常用工具

使用Spring RestTemplate 詳解實踐使用及拓展增強

目錄

RestTemplate 是什么？

主要類和接口

基礎(chǔ)使用

Post 發(fā)送對象或集合

上傳文件

上傳多個文件

Spring RestTemplate 拓展

繼承RestTemplate 拓展get方法

拓展URI處理邏輯

實際使用

思考進一步封裝

相關(guān)文章

最新評論

大家感興趣的內(nèi)容

最近更新的內(nèi)容

常用在線小工具

使用Spring RestTemplate 詳解實踐使用及拓展增強

目錄

RestTemplate 是什么？

主要類和接口

基礎(chǔ)使用

Post 發(fā)送對象或集合

上傳文件

上傳多個文件

Spring RestTemplate 拓展

繼承RestTemplate 拓展get方法

拓展URI處理邏輯

實際使用

思考進一步封裝

相關(guān)文章

最新評論

大家感興趣的內(nèi)容

最近更新的內(nèi)容

常用在線小工具

RestTemplate 是什么？