Description:
I am encountering a NullPointerException while trying to use the RestTemplate in combination with the MinimalHttpClient from the httpcomponents package to connect to external services. The error occurs when executing a request.
Steps to Reproduce:
- Clone the minimum reproducible example from [this link](https://github.com/ojas-krishnaprasad/demo/tree/master/demo).
- Run the application.
- Call the controller http://localhost:8080/test-library
Observed Behavior:
The error is thrown from the spring-web module, specifically in the method HttpComponentsClientHttpRequest#executeInternal.
Stack Trace:
java.lang.NullPointerException: Target host
at java.base/java.util.Objects.requireNonNull(Objects.java:259) ~[na:na]
at org.apache.hc.core5.util.Args.notNull(Args.java:165) ~[httpcore5-5.3.5.jar:5.3.5]
at org.apache.hc.client5.http.impl.classic.MinimalHttpClient.doExecute(MinimalHttpClient.java:113) ~[httpclient5-5.5.jar:5.5]
at org.apache.hc.client5.http.impl.classic.CloseableHttpClient.execute(CloseableHttpClient.java:87) ~[httpclient5-5.5.jar:5.5]
at org.apache.hc.client5.http.impl.classic.CloseableHttpClient.execute(CloseableHttpClient.java:55) ~[httpclient5-5.5.jar:5.5]
at org.apache.hc.client5.http.classic.HttpClient.executeOpen(HttpClient.java:183) ~[httpclient5-5.5.jar:5.5]
at org.springframework.http.client.HttpComponentsClientHttpRequest.executeInternal(HttpComponentsClientHttpRequest.java:99) ~[spring-web-7.0.0-M9.jar:7.0.0-M9]
at org.springframework.http.client.AbstractStreamingClientHttpRequest.executeInternal(AbstractStreamingClientHttpRequest.java:70) ~[spring-web-7.0.0-M9.jar:7.0.0-M9]
at org.springframework.http.client.AbstractClientHttpRequest.execute(AbstractClientHttpRequest.java:80) ~[spring-web-7.0.0-M9.jar:7.0.0-M9]
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:754) ~[spring-web-7.0.0-M9.jar:7.0.0-M9]
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:677) ~[spring-web-7.0.0-M9.jar:7.0.0-M9]
at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:304) ~[spring-web-7.0.0-M9.jar:7.0.0-M9]
Possible Cause:
It seems like the error is triggered by the MinimalHttpClient in the httpclient5 library, specifically when the target host is not provided or is null during the execution of the request. The issue appears to originate from the internal request execution in HttpComponentsClientHttpRequest.
Environment:
- Spring Web: 7.0.0-M9
- HttpClient: 5.5
- HttpCore: 5.3.5
Additional Information:
- I have confirmed that the error occurs with the minimal example provided.
- Any insights into why this issue might be happening would be greatly appreciated.
Comment From: ojas-krishnaprasad
In HttpComponentsClientHttpRequest#executeInternal
// Original Code:
this.httpClient.executeOpen((HttpHost) null, this.httpRequest, this.httpContext);
// Proposed Code:
this.httpClient.executeOpen(RoutingSupport.determineHost(this.httpRequest), this.httpRequest, this.httpContext);