java - 如何在 Spring Framework 中使用 RestTemplate 解析数组？
问题描述
我有一段 JSON 数据，它通过 Fixer API 来进行货币兑换。
http://data.fixer.io/api/latest?access_key=API_KEY&symbols=USD,INR&format=1
{
"success":true,
"timestamp":1593947225,
"base":"EUR",
"date":"2020-07-05",
"rates":{
"USD":1.1245,
"INR":83.977026
}
}
我需要使用 RestTemplate 读取rates 嵌套数组，并且我试图让这些类让它在没有运气的情况下工作！
最新价格控制器.java
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
@RestController
public class LatestRatesController {
@Value("${access_key}")
private String access_key;
@Autowired
private RestTemplate restTemplate;
@Bean
public RestTemplate restTemplate() {
return new RestTemplate();
}
@GetMapping("/latest-rates/from/EUR/to/{to}")
public ExchangeValue retrieveExchangeValue(@PathVariable("to") String to)
{
ExchangeValue exchangeValue = restTemplate.getForObject("http://data.fixer.io/api/latest?access_key=" + access_key
+"&symbols="+ to+"&format=1", ExchangeValue.class);
return exchangeValue;
}
}
ExchangeValue.java
public class ExchangeValue {
private boolean success;
private BigDecimal timestamp;
private String base;
private String date;
private List<String> rates;
protected ExchangeValue() {
}
public ExchangeValue(boolean success, BigDecimal timestamp, String base, String date) {
super();
this.success = success;
this.timestamp = timestamp;
this.base = base;
this.date = date;
}
public List<String> getRates() {
return rates;
}
public void setRates(List<String> rates) {
this.rates = rates;
}
public boolean isSuccess() {
return success;
}
public void setSuccess(boolean success) {
this.success = success;
}
public BigDecimal getTimestamp() {
return timestamp;
}
public void setTimestamp(BigDecimal timestamp) {
this.timestamp = timestamp;
}
public String getBase() {
return base;
}
public void setBase(String base) {
this.base = base;
}
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
}
Rates.java
public class Rates {
private String USD;
public Rates(String uSD) {
super();
USD = uSD;
}
public String getUSD() {
return USD;
}
public void setUSD(String uSD) {
USD = uSD;
}
}
实际上我需要读取可能通过 API URI 传递的任何其他货币，因此我制作的 Rates 类仅使用 USD 进行测试，当尝试运行它时出现此错误
Whitelabel Error Page
This application has no explicit mapping for /error, so you are seeing this as a fallback.
Sun Jul 05 14:44:12 EEST 2020
There was an unexpected error (type=Internal Server Error, status=500).
Error while extracting response for type [class com.fixer.microservices.latestratesservice.ExchangeValue] and content type [application/json;Charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of `java.util.ArrayList<java.lang.Object>` out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList<java.lang.Object>` out of START_OBJECT token at [Source: (PushbackInputStream); line: 6, column: 11] (through reference chain: com.fixer.microservices.latestratesservice.ExchangeValue["rates"])
org.springframework.web.client.RestClientException: Error while extracting response for type [class com.fixer.microservices.latestratesservice.ExchangeValue] and content type [application/json;Charset=UTF-8]; nested exception is org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of `java.util.ArrayList<java.lang.Object>` out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList<java.lang.Object>` out of START_OBJECT token
at [Source: (PushbackInputStream); line: 6, column: 11] (through reference chain: com.fixer.microservices.latestratesservice.ExchangeValue["rates"])
at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:120)
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:741)
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:674)
at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:315)
at com.fixer.microservices.latestratesservice.LatestRatesController.retrieveExchangeValue(LatestRatesController.java:30)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190)
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138)
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879)
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793)
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87)
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040)
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943)
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006)
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:634)
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.boot.actuate.metrics.web.servlet.WebMvcMetricsFilter.doFilterInternal(WebMvcMetricsFilter.java:93)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201)
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373)
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65)
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868)
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590)
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Unknown Source)
Caused by: org.springframework.http.converter.HttpMessageNotReadableException: JSON parse error: Cannot deserialize instance of `java.util.ArrayList<java.lang.Object>` out of START_OBJECT token; nested exception is com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList<java.lang.Object>` out of START_OBJECT token
at [Source: (PushbackInputStream); line: 6, column: 11] (through reference chain: com.fixer.microservices.latestratesservice.ExchangeValue["rates"])
at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:275)
at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:257)
at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:105)
... 58 more
Caused by: com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of `java.util.ArrayList<java.lang.Object>` out of START_OBJECT token
at [Source: (PushbackInputStream); line: 6, column: 11] (through reference chain: com.fixer.microservices.latestratesservice.ExchangeValue["rates"])
at com.fasterxml.jackson.databind.exc.MismatchedInputException.from(MismatchedInputException.java:59)
at com.fasterxml.jackson.databind.DeserializationContext.reportInputMismatch(DeserializationContext.java:1464)
at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1238)
at com.fasterxml.jackson.databind.DeserializationContext.handleUnexpectedToken(DeserializationContext.java:1148)
at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.handleNonArray(StringCollectionDeserializer.java:274)
at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:183)
at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:173)
at com.fasterxml.jackson.databind.deser.std.StringCollectionDeserializer.deserialize(StringCollectionDeserializer.java:21)
at com.fasterxml.jackson.databind.deser.impl.MethodProperty.deserializeAndSet(MethodProperty.java:129)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserializeFromObject(BeanDeserializer.java:371)
at com.fasterxml.jackson.databind.deser.BeanDeserializer.deserialize(BeanDeserializer.java:164)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4482)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3487)
at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:269)
... 60 more
解决方案
您的费率对象不是 JSONArray，而是另一个 JSONObject。因此，要将其转换为 Java 对象，更好的数据结构将是哈希映射。
因此，您不需要 Rates 类。
您可以像这样定义 ExchangeValue 类：
public class ExchangeValue {
private boolean success;
private BigDecimal timestamp;
private String base;
private String date;
private Map<String,Double> rates;
protected ExchangeValue() {
}
public ExchangeValue(boolean success, BigDecimal timestamp, String base, String date, Map<String, Double> rates) {
this.success = success;
this.timestamp = timestamp;
this.base = base;
this.date = date;
this.rates = rates;
}
public Map<String, Double> getRates() {
return rates;
}
public void setRates(Map<String, Double> rates) {
this.rates = rates;
}
public boolean isSuccess() {
return success;
}
public void setSuccess(boolean success) {
this.success = success;
}
public BigDecimal getTimestamp() {
return timestamp;
}
public void setTimestamp(BigDecimal timestamp) {
this.timestamp = timestamp;
}
public String getBase() {
return base;
}
public void setBase(String base) {
this.base = base;
}
public String getDate() {
return date;
}
public void setDate(String date) {
this.date = date;
}
}
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