RestTemplate 是什么？
RestTemplate 是 Spring 封装的一个Rest风格http请求框架，底层可以切换成HttpClient OkHttp 或者Netty实现，用户只需要关心RestTemplate怎么用而不需要关心底层框架如何操作，使用RestTemplate不需要关心如何手动转换返回的对象和到处都是的异常处理代码，可以让你的代码更简洁更优雅。
你可以在 spring-web 中找到它
主要类和接口
RestOperations 定义Rest 操作的接口 HttpAccessor 抽象http help 类 InterceptingHttpAccessor HttpAccess 装饰类拓展了拦截器功能 RestTemplate 具体实现类 ClientHttpRequestInterceptor 拦截器接口 用于拦截http请求 UriTemplateHandler uri 模板处理器，后面拓展会用到
基础使用
put delete 等方法参考get post 的写法
Get获取对象或对象集合
获取 Employee 集合
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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(); |
返回对象list用exchange方法使用 ParameterizedTypeReference 指定返回类型 ，getForEntity 也可以使用 Object[].class 或 其他数组接收再转为List
获取单个对象
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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 发送对象或集合
发送集合
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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 ); |
发送对象
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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 ); |
上传文件
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public void uploadFile(){ HttpHeaders headers = new HttpHeaders(); //设置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中的一个类 参考
上传多个文件
在上传单个文件的基础上多加几个文件
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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
解决restTemplate get* url参数必须写死的问题 解决get*方法不好添加header信息的问题
继承RestTemplate 拓展get方法
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/** * 继承RestTemplate 新加get* 方法 比原有的方法多了个 httpHeaders 参数 */ 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处理逻辑
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/** * 根据uriTemplate 把 uriVariables 分成两类 * 一类是path params 一类是 query params 分开赋值 * 如 /xx/{id}/type path params 就是 id uriVariables 剩下的就是query params 用？拼接在url后面 * 如果查询参数中有数组或集合类型的参数会转化成 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); //设置query param queryParam.forEach((k, v) -> { if (v instanceof Object[]) { Object[] arrayParam = (Object[]) v; //把数组类型的参数拼成 参数名 + [] 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(); //设置path param return super .expand(uriTemplate, uriVariables); } /** * 解析uriTemplate 分离 query param * * @param uriTemplate uri模板 * @param uriVariables 全部的模板变量 * @return 查询变量 */ 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); } } //此处为了图方便使用了 guava 工具包中的类 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(); } } |
实际使用
初始化RestTemplate
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SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory(); requestFactory.setConnectTimeout( 500 ); // 设置超时 requestFactory.setReadTimeout( 500 ); //new 自己定义的类 CustomerRestTemplate restTemplate = new CustomerRestTemplate(); //设置自定义的uri处理处理器 QueryParamsUrlTemplateHandler queryParamsUrlTemplateHandler = new QueryParamsUrlTemplateHandler(); //这里使用装饰模式 添加rootUri RootUriTemplateHandler rootUriTemplateHandler = new RootUriTemplateHandler(outUrl, queryParamsUrlTemplateHandler); restTemplate.setUriTemplateHandler(rootUriTemplateHandler); restTemplate.setRequestFactory(requestFactory); |
get请求示例
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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 为 api/test/1?param[]=1506¶m[]=1507¶m2=2 |
思考进一步封装
可以考虑使用建造者模式改造restTemplate
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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(); |
以上为个人经验，希望能给大家一个参考，也希望大家多多支持。
原文链接：https://blog.csdn.net/isyoungboy/article/details/86608877
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