使用Spring RestTemplate 详解实践使用及拓展增强

使用Spring RestTemplate 详解实践使用及拓展增强

目录RestTemplate 是什么？主要类和接口基础使用Get获取对象或对象集合Post 发送对象或集合上传文件上传多个文件Spring RestTemplate 拓展继承RestTemplate 拓展get方法拓展URI处理逻辑实际使用思考进一步封装

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

RestTemplate restTemplate = new RestTemplate();

ResponseEntity> response = restTemplate.exchange(

"http://localhost:8080/employees/",

HttpMethod.GET,

null,

new ParameterizedTypeReference>(){});

List 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

public class EmployeeList {

private List employees;

public EmployeeList() {

employees = new ArrayList<>();

}

// getter/setter

}

EmployeeList response = restTemplate.getForObject(

"http://localhost:8080/employees",

EmployeeList.class);

List employees = response.getEmployees();

Post 发送对象或集合

发送集合

List 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

List 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

public void uploadFile(){

HttpHeaders headers = new HttpHeaders();

//设置Content-Type

headers.setContentType(MediaType.MULTIPART_FORM_DATA);

MultiValueMap body

= new LinkedMultiValueMap<>();

body.add("file", getTestFile());

HttpEntity> requestEntity

= new HttpEntity<>(body, headers);

String serverUrl = "http://localhost:8082/spring-rest/fileserver/singlefileupload/";

RestTemplate restTemplate = new RestTemplate();

ResponseEntity 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

MultiValueMap body

= new LinkedMultiValueMap<>();

body.add("files", getTestFile());

body.add("files", getTestFile());

body.add("files", getTestFile());

HttpEntity> requestEntity

= new HttpEntity<>(body, headers);

String serverUrl = "http://localhost:8082/spring-rest/fileserver/multiplefileupload/";

RestTemplate restTemplate = new RestTemplate();

ResponseEntity 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

/**

* 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 ResponseEntity getForEntity(String url, HttpHeaders httpHeaders, Class responseType, Object... uriVariables) throws RestClientException {

HttpEntity

RequestCallback requestCallback = httpEntityCallback(requestEntity, responseType);

ResponseExtractor> responseExtractor = responseEntityExtractor(responseType);

return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);

}

public ResponseEntity getForEntity(String url, HttpHeaders httpHeaders, Class responseType, Map uriVariables) throws RestClientException {

HttpEntity

RequestCallback requestCallback = httpEntityCallback(requestEntity, responseType);

ResponseExtractor> responseExtractor = responseEntityExtractor(responseType);

return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);

}

public T getForObject(String url, HttpHeaders httpHeaders, Class responseType, Map uriVariables) throws RestClientException {

HttpEntity

RequestCallback requestCallback = httpEntityCallback(requestEntity, responseType);

ResponseExtractor responseExtractor = new HttpMessageConverterExtractor(responseType, getMessageConverters());

return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);

}

public T getForObject(String url, HttpHeaders httpHeaders, Class responseType, Object... uriVariables) throws RestClientException {

HttpEntity

RequestCallback requestCallback = httpEntityCallback(requestEntity, responseType);

ResponseExtractor responseExtractor = new HttpMessageConverterExtractor(responseType, getMessageConverters());

return execute(url, HttpMethod.GET, requestCallback, responseExtractor, uriVariables);

}

}

拓展URI处理逻辑

/**

* 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 uriVariables) {

UriComponentsBuilder uriComponentsBuilder = UriComponentsBuilder.fromHttpUrl(uriTemplate);

//解析uriTemplate 提取query param

Map 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 getQueryParam(String uriTemplate, Map uriVariables) {

if (uriTemplate == null) {

return null;

}

if (uriTemplate.indexOf('{') == -1) {

return uriVariables;

}

if (uriTemplate.indexOf(':') != -1) {

uriTemplate = sanitizeSource(uriTemplate);

}

Map 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 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

SimpleClientHttpRequestFactory requestFactory = new SimpleClientHttpRequestFactory();

requestFactorhttp://y.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

Map 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

// url 为 api/test/1?param[]=1506&param[]=1507&param2=2

思考进一步封装

可以考虑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();

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