WebClient HTTP 请求问题处理模板（泛型响应、忽略 SSL 证书等）
我命由我12345 2024-09-12 12:33:10 阅读 98
一、请求大数据
1、问题案例
（1）Server
该接口返回一段大小为 1MB 的字符串
<code>@GetMapping("/testBigData")
public String testBigData() {
int targetSize = 1024 * 1024; // 1MB
StringBuilder sb = new StringBuilder(targetSize);
for (int i = 0; i < targetSize; i++) sb.append('A');
String largeString = sb.toString();
return largeString;
}
（2）Client
WebClient webClient = WebClient.create();
Mono<String> response = webClient.get()
.uri("http://127.0.0.1:9999/test/testBigData")
.retrieve()
.bodyToMono(String.class);
response.subscribe(result -> {
System.out.println("请求成功，结果长度为：" + result.length());
}, throwable -> {
throwable.printStackTrace();
});
输出结果，因为数据量超过了设定的最大限制而报错
org.springframework.web.reactive.function.client.WebClientResponseException: 200 OK from GET http://127.0.0.1:9999/test/testBigData
Caused by: org.springframework.core.io.buffer.DataBufferLimitException: Exceeded limit on max bytes to buffer : 262144
2、处理策略
调整数据量的最大限制
int size = 2 * 1024 * 1024;
ExchangeStrategies strategies = ExchangeStrategies.builder()
.codecs(codecs -> codecs.defaultCodecs().maxInMemorySize(size))
.build();
WebClient webClient = WebClient.builder()
.exchangeStrategies(strategies)
.build();
Mono<String> response = webClient.get()
.uri("http://127.0.0.1:9999/test/testBigData")
.retrieve()
.bodyToMono(String.class);
response.subscribe(result -> {
System.out.println("请求成功，结果长度为：" + result.length());
}, throwable -> {
throwable.printStackTrace();
});
二、不使用缓冲区请求图片
1、问题案例
（1）Server
application.yaml
server:
port: 9999
spring:
mvc:
static-path-pattern: /file/download/**
web:
resources:
static-locations: file:D:/fileUpload/
（2）Client
WebClient webClient = WebClient.create();
Mono<byte[]> response = webClient.get()
.uri("http://127.0.0.1:9999/file/download/1.png")
.accept(MediaType.IMAGE_JPEG, MediaType.IMAGE_PNG)
.retrieve()
.bodyToMono(byte[].class);
response.subscribe(result -> {
System.out.println("请求成功");
if (result != null) System.out.println("result length is " + result.length);
}, throwable -> {
throwable.printStackTrace();
});
输出结果，不使用 DataBuffer，会因为数据量超过了设定的最大限制而报错
org.springframework.web.reactive.function.client.WebClientResponseException: 200 OK from GET http://127.0.0.1:9999/file/download/1.png
Caused by: org.springframework.core.io.buffer.DataBufferLimitException: Exceeded limit on max bytes to buffer : 262144
2、处理策略
调整数据量的最大限制
int size = 10 * 1024 * 1024;
ExchangeStrategies strategies = ExchangeStrategies.builder()
.codecs(codecs -> codecs.defaultCodecs().maxInMemorySize(size))
.build();
WebClient webClient = WebClient.builder()
.exchangeStrategies(strategies)
.build();
Mono<byte[]> response = webClient.get()
.uri("http://127.0.0.1:9999/file/download/1.png")
.accept(MediaType.IMAGE_JPEG, MediaType.IMAGE_PNG)
.retrieve()
.bodyToMono(byte[].class);
response.subscribe(result -> {
System.out.println("请求成功");
if (result != null) System.out.println("result length is " + result.length);
}, throwable -> {
throwable.printStackTrace();
});
三、泛型响应
1、问题案例
（1）Entity
Person.java
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Person<T> {
private String name;
private int age;
private T thing;
}
Computer.java
@Data
@NoArgsConstructor
@AllArgsConstructor
public class Computer {
private String name;
private Double price;
}
（2）Server
@GetMapping("/testGeneric")
public Person<Computer> testGeneric() {
Computer computer = new Computer("联想电脑", 8999.0);
Person<Computer> person = new Person<Computer>("张三", 20, computer);
return person;
}
（3）Client
WebClient webClient = WebClient.create();
Mono<Person> response = webClient.get()
.uri("http://127.0.0.1:9999/test/testGeneric")
.retrieve()
.bodyToMono(Person.class);
response.subscribe(person -> {
System.out.println("请求成功");
System.out.println(person);
Computer computer = (Computer) person.getThing();
System.out.println(computer);
}, throwable -> {
System.out.println("请求失败，结果为：" + throwable.getMessage());
});
输出结果，对于嵌套的泛型强转失败
请求成功
Person(name=张三, age=20, thing={name=联想电脑, price=8999.0})
请求失败，结果为：class java.util.LinkedHashMap cannot be cast to class com.zy.api.Computer (java.util.LinkedHashMap is in module java.base of loader 'bootstrap'; com.zy.api.Computer is in unnamed module of loader 'app')
2、处理策略
正确指示 bodyToMono 方法
WebClient webClient = WebClient.create();
Mono<Person<Computer>> response = webClient.get()
.uri("http://127.0.0.1:9999/test/testGeneric")
.retrieve()
.bodyToMono(new ParameterizedTypeReference<Person<Computer>>() {
});
response.subscribe(person -> {
System.out.println("请求成功");
System.out.println(person);
Computer computer = person.getThing();
System.out.println(computer);
}, throwable -> {
System.out.println("请求失败，结果为：" + throwable.getMessage());
});
四、跟随重定向响应
1、问题案例
（1）Server
server:
port: 9999
spring:
mvc:
static-path-pattern: /file/download/**
web:
resources:
static-locations: file:D:/fileUpload/
@GetMapping("/testRedirect2Image")
public ResponseEntity testRedirect2Image() {
return ResponseEntity.status(HttpStatus.SEE_OTHER)
.header("Location", "http://127.0.0.1:9999/file/download/1.png")
.build();
}
（2）Client
WebClient webClient = WebClient.create();
webClient.get()
.uri("http://127.0.0.1:9999/test/testRedirect2Image")
.accept(MediaType.IMAGE_JPEG, MediaType.IMAGE_PNG) // 指定了客户端期望接受的响应内容类型
.retrieve() // 获取响应
.bodyToFlux(DataBuffer.class) // 将响应体转换为 Flux<DataBuffer>
.reduce(new org.apache.tomcat.util.http.fileupload.ByteArrayOutputStream(), (baos, dataBuffer) -> {
try {
byte[] bytes = new byte[dataBuffer.readableByteCount()];
dataBuffer.read(bytes);
baos.write(bytes);
DataBufferUtils.release(dataBuffer);
} catch (IOException e) {
e.printStackTrace();
DataBufferUtils.release(dataBuffer);
return null;
}
return baos;
})
.map(byteArrayOutputStream -> {
if (byteArrayOutputStream == null) return null;
return byteArrayOutputStream.toByteArray();
})
.subscribe(result -> {
if (result == null) {
System.out.println("result is null");
return;
}
System.out.println("result length: " + result.length);
}, throwable -> {
throwable.printStackTrace();
});
输出结果，默认不会跟随重定向响应
result length: 0
2、处理策略
收到开启跟随重定向响应
HttpClient httpClient = HttpClient.create()
.followRedirect(true); // 允许跟随重定向
WebClient webClient = WebClient.builder()
.clientConnector(new ReactorClientHttpConnector(httpClient))
.build();
webClient.get()
.uri("http://127.0.0.1:9999/test/testRedirect2Image")
.accept(MediaType.IMAGE_JPEG, MediaType.IMAGE_PNG) // 指定了客户端期望接受的响应内容类型
.retrieve() // 获取响应
.bodyToFlux(DataBuffer.class) // 将响应体转换为 Flux<DataBuffer>
.reduce(new org.apache.tomcat.util.http.fileupload.ByteArrayOutputStream(), (baos, dataBuffer) -> {
try {
byte[] bytes = new byte[dataBuffer.readableByteCount()];
dataBuffer.read(bytes);
baos.write(bytes);
DataBufferUtils.release(dataBuffer);
} catch (IOException e) {
e.printStackTrace();
DataBufferUtils.release(dataBuffer);
return null;
}
return baos;
})
.map(byteArrayOutputStream -> {
if (byteArrayOutputStream == null) return null;
return byteArrayOutputStream.toByteArray();
})
.subscribe(result -> {
if (result == null) {
System.out.println("result is null");
return;
}
System.out.println("result length: " + result.length);
}, throwable -> {
throwable.printStackTrace();
});
五、SSL 证书
1、问题案例
WebClient webClient = WebClient.create();
Mono<byte[]> response = webClient.get()
.uri(url)
.accept(MediaType.IMAGE_JPEG, MediaType.IMAGE_PNG)
.retrieve()
.bodyToFlux(DataBuffer.class)
.reduce(new ByteArrayOutputStream(), (baos, dataBuffer) -> {
try {
byte[] bytes = new byte[dataBuffer.readableByteCount()];
dataBuffer.read(bytes);
baos.write(bytes);
DataBufferUtils.release(dataBuffer);
} catch (IOException e) {
e.printStackTrace();
DataBufferUtils.release(dataBuffer);
return null;
}
return baos;
})
.map(byteArrayOutputStream -> {
if (byteArrayOutputStream == null) return null;
return byteArrayOutputStream.toByteArray();
});
response.subscribe(result -> {
System.out.println("请求成功");
if (result != null) System.out.println("result length is " + result.length);
}, throwable -> {
throwable.printStackTrace();
});
输出结果
org.springframework.web.reactive.function.client.WebClientRequestException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
2、忽略 SSL 证书
SslContext context = SslContextBuilder.forClient().trustManager(InsecureTrustManagerFactory.INSTANCE).build();
HttpClient httpClient = HttpClient.create().secure(t -> t.sslContext(context));
WebClient webClient = WebClient.builder()
.clientConnector(new ReactorClientHttpConnector(httpClient))
.build();
Mono<byte[]> response = webClient.get()
.uri(url)
.accept(MediaType.IMAGE_JPEG, MediaType.IMAGE_PNG)
.retrieve()
.bodyToFlux(DataBuffer.class)
.reduce(new ByteArrayOutputStream(), (baos, dataBuffer) -> {
try {
byte[] bytes = new byte[dataBuffer.readableByteCount()];
dataBuffer.read(bytes);
baos.write(bytes);
DataBufferUtils.release(dataBuffer);
} catch (IOException e) {
e.printStackTrace();
DataBufferUtils.release(dataBuffer);
return null;
}
return baos;
})
.map(byteArrayOutputStream -> {
if (byteArrayOutputStream == null) return null;
return byteArrayOutputStream.toByteArray();
});
response.subscribe(result -> {
System.out.println("请求成功");
if (result != null) System.out.println("result length is " + result.length);
}, throwable -> {
throwable.printStackTrace();
});
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