Springboot使用RestTemplate发送Post请求postForEntity (application/json)的坑

anita9999

13354人浏览 · 2020-09-27 17:56:49

anita9999 · 2020-09-27 17:56:49 发布

当使用RestTemplate进行http请求时，的确很方便，但是当需要进行post请求时遇到了坑

1POST传递参数：采用 LinkedMultiValueMap ，不能使用HashMap

String url = 'http://posturl';
MultiValueMap<String, String> map= new LinkedMultiValueMap<String, String>();
map.add("shopid","1");
HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<MultiValueMap<String, String>>(map, headers);
return restTemplate.postForEntity(url, request,String.class);

注意上面的请求支持参数类型均为String类型，如果MultiValueMap<String, Object> LinkedMultiValueMap 会将value放进list中，key --> [value]

2 采用JSONObject或者实体类传递参数

RestTemplate restTemplate = new RestTemplate();
HttpHeaders headers = new HttpHeaders();
MediaType type = MediaType.parseMediaType("application/json; charset=UTF-8");
headers.setContentType(type);
headers.add("Accept", MediaType.APPLICATION_JSON.toString());
JSONObject param = new JSONObject();
param.put("username", "123");
HttpEntity<String> formEntity = new HttpEntity<String>(param, headers);
String result = restTemplate.postForObject(url, formEntity, String.class);

使用这种方式可以传递任意类型的参数，避免上面的情况

总结，遇到这种问题时多看看源码会很有帮助。

public class LinkedMultiValueMap<K, V> implements MultiValueMap<K, V>, Serializable, Cloneable {
private static final long serialVersionUID = 3801124242820219131L;
private final Map<K, List<V>> targetMap;
public LinkedMultiValueMap() {
this.targetMap = new LinkedHashMap();
}
public LinkedMultiValueMap(int initialCapacity) {
this.targetMap = new LinkedHashMap(initialCapacity);
}
public LinkedMultiValueMap(Map<K, List<V>> otherMap) {
this.targetMap = new LinkedHashMap(otherMap);
}
@Nullable
public V getFirst(K key) {
List<V> values = (List)this.targetMap.get(key);
return values != null && !values.isEmpty() ? values.get(0) : null;
}
public void add(K key, @Nullable V value) {
List<V> values = (List)this.targetMap.computeIfAbsent(key, (k) -> {
return new LinkedList();
});
values.add(value);
}
public void addAll(K key, List<? extends V> values) {
List<V> currentValues = (List)this.targetMap.computeIfAbsent(key, (k) -> {
return new LinkedList();
});
currentValues.addAll(values);
}
public void addAll(MultiValueMap<K, V> values) {
Iterator var2 = values.entrySet().iterator();
while(var2.hasNext()) {
Entry<K, List<V>> entry = (Entry)var2.next();
this.addAll(entry.getKey(), (List)entry.getValue());
}
}
public void set(K key, @Nullable V value) {
List<V> values = new LinkedList();
values.add(value);
this.targetMap.put(key, values);
}
public void setAll(Map<K, V> values) {
values.forEach(this::set);
}
public Map<K, V> toSingleValueMap() {
LinkedHashMap<K, V> singleValueMap = new LinkedHashMap(this.targetMap.size());
this.targetMap.forEach((key, values) -> {
if (values != null && !values.isEmpty()) {
singleValueMap.put(key, values.get(0));
}
});
return singleValueMap;
}