49 lines
1.7 KiB
Markdown
49 lines
1.7 KiB
Markdown
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## 使用RestTemplate优雅的发送Get请求
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在我们的项目中，如果借助 [RestTemplate](https://so.csdn.net/so/search?q=RestTemplate&spm=1001.2101.3001.7020) 发送带参数的 Get 请求，我们可以通过拼接字符串的方式将 url 拼接出来，比如下面这种方式：
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```java
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String url = "http://127.0.0.1:8080/rest/get? + id;
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ResponseEntity<RestVO> forEntity = restTemplate.getForEntity(url, RestVO.class);
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```
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然而这种方式不太优雅，我们还可以通过以下几种方式发送 Get 请求
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#### 方式 1：使用占位符
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```java
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String url = "http://127.0.0.1:8080/rest/path/{name}/{id}";
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Map<String, Object> params = new HashMap<>();
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params.put("name", "这是name");
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params.put("id", 1L);
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ResponseEntity<RestVO> forEntity = restTemplate.getForEntity(url, RestVO.class, params);
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```
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Map 的 key 要和 `url `中的占位符一致
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#### 方式 2：使用 LinkedMultiValueMap 和 UriComponentsBuilder
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```java
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String url = "http://127.0.0.1:8080/rest/get";
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MultiValueMap<String, String> params = new LinkedMultiValueMap<>();
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params.add("name", "这是name");
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params.add("id", "1");
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UriComponentsBuilder builder = UriComponentsBuilder.fromHttpUrl(url);
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URI uri = builder.queryParams(params).build().encode().toUri();
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ResponseEntity<RestVO> forEntity = restTemplate.getForEntity(uri, RestVO.class);
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return forEntity.getBody();
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```
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方式 2 看起来是最优雅的，将参数的设置和 `url `分离。
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#### Map 转 MultiValueMap
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```java
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Map<String,String> params = new HashMap<>();
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MultiValueMap<String, String> multiValueMap = new LinkedMultiValueMap<>(
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params.entrySet().stream().collect(
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Collectors.toMap(Map.Entry::getKey, e -> Collections.singletonList(e.getValue()))));
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```
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