如何Mock RestTemplate的exchange方法？遇参数不匹配报错求助

问题场景 #

我尝试Mock RestTemplate的exchange方法，代码如下：

String responseBody = "responseBody";
String url = "http://example.com";
HttpMethod method = HttpMethod.GET;
HttpEntity<String> requestEntity = null;
Class<String> responseType = String.class;
Object[] uriVariables = {};
    
Map<String, String> headers = Collections.singletonMap("key", "value");
when(restTemplate.exchange(url, HttpMethod.GET, requestEntity, responseType, uriVariables))
    .thenReturn(new ResponseEntity<>(responseBody, HttpStatus.OK));

运行时出现如下错误：

Description Resource    Path    Location    Type
The method exchange(String, HttpMethod, HttpEntity<?>, Class<T>, Object...) in the type RestTemplate 
    is not applicable for the arguments (String, HttpMethod, HttpEntity<String>, Class<String>, Object[])   line 45 Java Problem

无法定位参数错误原因，求解答。

错误原因与解决方法 #

错误根源 #

问题出在最后一个参数uriVariables的类型匹配上：RestTemplate的exchange方法最后一个参数是可变参数Object...，虽然可变参数底层基于数组实现，但直接传递Object[]类型变量时，编译器会将其视为单个数组参数，而非展开成可变参数列表，导致方法签名不匹配。

修复方案 #

有三种可行的修复方式：

1. 直接传递空可变参数
   既然uriVariables是空数组，可直接省略该参数，或显式传递空可变参数：

   // 省略空可变参数
   when(restTemplate.exchange(url, HttpMethod.GET, requestEntity, responseType))
       .thenReturn(new ResponseEntity<>(responseBody, HttpStatus.OK));
   

   或者：

   // 显式传递空参数列表
   when(restTemplate.exchange(url, HttpMethod.GET, requestEntity, responseType, new Object[0]))
       .thenReturn(new ResponseEntity<>(responseBody, HttpStatus.OK));
   

2. 强制将数组转为单个参数传递
   如果uriVariables有实际值，不想拆分为可变参数，可将其强制转换为Object类型，让编译器将其视为可变参数的单个元素：

   when(restTemplate.exchange(url, HttpMethod.GET, requestEntity, responseType, (Object) uriVariables))
       .thenReturn(new ResponseEntity<>(responseBody, HttpStatus.OK));
   

3. 使用Mockito匹配器简化匹配
   若无需精确匹配参数，使用Mockito的匹配器可规避类型匹配问题：

   when(restTemplate.exchange(eq(url), eq(HttpMethod.GET), any(HttpEntity.class), eq(String.class), any(Object[].class)))
       .thenReturn(new ResponseEntity<>(responseBody, HttpStatus.OK));
   

内容的提问来源于stack exchange，提问作者user4599