java - LinkedMultiValueMap SpringFramework 未迭代（错误：无法转换为类）
问题描述
我尝试使用以下方法迭代 springframework.LinkedMultiValueMap：
- 迭代器
- 前锋
- 流.foreach
- 尽管
- collections.values().foreach
- 数独（开玩笑）
但先后得到错误：不能强制转换为类
这是代码：
package com.br.aloi.planner.controller;
import java.io.IOException;
import java.util.Collection;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import javax.validation.Valid;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.servlet.ModelAndView;
import com.br.aloi.planner.model.CSVModel;
import com.br.aloi.planner.model.CSVModelAttributes;
import com.br.aloi.planner.service.CSVService;
import com.br.aloi.planner.service.MapsApiService;
import com.google.gson.Gson;
import com.google.gson.JsonParser;
import com.google.maps.errors.ApiException;
@Controller
public class CustomerController {
String query;
@Autowired
private CSVService CSVservice;
@GetMapping("/planner")
public ModelAndView getPlanner(
@RequestParam(value = "sortBy", defaultValue = "id", required = false) String sortParam,
@RequestParam(value = "action", required = false) Optional<String> action)
throws ApiException, InterruptedException, IOException {
ModelAndView mv = new ModelAndView("/planner");
Optional<CSVModel> csvModel = CSVservice.findById(0); //0 is just for test the linkedvaluemap
/* this is the linkedvaluemap. Created converting a
"json linkedvaluemap string" to a linkedvaluemap, with gson's help. */
@SuppressWarnings("unchecked")
final LinkedMultiValueMap<Integer, CSVModelAttributes> attrib = new Gson().fromJson(
(csvModel.get().getAttributes()), LinkedMultiValueMap.class);
/* HERE i create a collection only with the values of each entry
of linkedvaluemap. the values are a list of CSVModelAttributes */
Collection<List<CSVModelAttributes>> valuesOfAttrib = attrib.values();
/* HERE i run each one collections values to get the list of
CSVModelAttribues and after get the attribute getValue() of each model */
for (List<CSVModelAttributes> value : valuesOfAttrib) {
int i = 0;
while (i < value.size()) {
query += value.get(i).getValue() + "+";
i++;
}
System.out.println(query);
System.out.println(MapsApiService.getLat(query));
}
mv.addObject("csvModels", CSVservice.sortBy(csvModels, sortParam));
return mv;
}
}
CSVModelAttributes 类
package com.br.aloi.planner.model;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import com.google.gson.Gson;
@SuppressWarnings("serial")
@Entity(name = "tbl_modelAttributes")
public class CSVModelAttributes implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;
@Column
private Integer modelId;
@Column(columnDefinition = "TEXT")
private String key;
@Column(columnDefinition = "TEXT")
private String value;
public CSVModelAttributes() {
}
public CSVModelAttributes(String key, String value) {
this.modelId = modelId;
this.key = key;
this.value = value;
}
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public Integer getModelId() {
return modelId;
}
public void setModelId(Integer modelId) {
this.modelId = modelId;
}
public String getKey() {
return key;
}
public void setKey(String key) {
this.key = key;
}
public String getValue() {
return value;
}
public void setValue(String value) {
this.value = value;
}
@Override
public String toString() {
return new Gson().toJson(this);
}
}
CSVModel 类
package com.br.aloi.planner.model;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.validation.constraints.Size;
import lombok.AllArgsConstructor;
@SuppressWarnings("serial")
@Entity(name = "tbl_csv")
@AllArgsConstructor
public class CSVModel implements Serializable {
@Id
private Integer id;
@Column(length = 1024)
@Size(max = 1024)
private String attributes;
public CSVModel() {
}
public Integer getId() {
return id;
}
public Integer setId(Integer id) {
return this.id = id;
}
public String getAttributes() {
return attributes;
}
public void setAttributes(String attributes) {
this.attributes = attributes;
}
}
错误：
java.lang.ClassCastException: class com.google.gson.internal.LinkedTreeMap cannot be cast to class com.br.aloi.planner.model.CSVModelAttributes (com.google.gson.internal.LinkedTreeMap and com.br.aloi.planner.model.CSVModelAttributes are in unnamed module of loader 'app')
at com.br.aloi.planner.controller.CustomerController.getPlanner(CustomerController.java:63) ~[classes/:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:na]
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:na]
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:na]
at java.base/java.lang.reflect.Method.invoke(Method.java:564) ~[na:na]
at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:190) ~[spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:138) ~[spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:105) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:879) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:793) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:87) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1040) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:943) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1006) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:898) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:634) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:883) ~[spring-webmvc-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at javax.servlet.http.HttpServlet.service(HttpServlet.java:741) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) ~[tomcat-embed-websocket-9.0.36.jar:9.0.36]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:100) ~[spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.springframework.web.filter.FormContentFilter.doFilterInternal(FormContentFilter.java:93) ~[spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:201) ~[spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:119) ~[spring-web-5.2.7.RELEASE.jar:5.2.7.RELEASE]
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:541) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:373) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:65) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:868) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1590) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) ~[na:na]
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:630) ~[na:na]
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) ~[tomcat-embed-core-9.0.36.jar:9.0.36]
at java.base/java.lang.Thread.run(Thread.java:832) ~[na:na]
JSON 字符串
{0=[{"key":"customerId","value":"4891"}, {"key":"companyName","value":"GIOVANE FERREIRA"}, {"key":"place","value":"AV AV TEPEQUEM SN"}, {"key":"neighborhood","value":"CENTRO"}, {"key":"city","value":"AMAJARI"}, {"key":"a","value":"RR"}, {"key":"postalCode","value":"69300000"}, {"key":"c","value":"ISENTO"}, {"key":"tradeName","value":"CIA DO GELO"}, {"key":"sectorId","value":"301"}, {"key":"region","value":"RR"}]}
2 天没有解决方案，我几乎要摆脱这个库并放置 apache commons 集合。
解决方案
@SuppressWarnings("unchecked")
final LinkedMultiValueMap<Integer, CSVModelAttributes> attrib = new Gson().fromJson(
(csvModel.get().getAttributes()), LinkedMultiValueMap.class);
这条线有问题。
{0=[{"key":"customerId","value":"4891"}, {"key":"companyName","value":"GIOVANE FERREIRA"}, {"key":"place","value":"AV AV TEPEQUEM SN"}, {"key":"neighborhood","value":"CENTRO"}, {"key":"city","value":"AMAJARI"}, {"key":"a","value":"RR"}, {"key":"postalCode","value":"69300000"}, {"key":"c","value":"ISENTO"}, {"key":"tradeName","value":"CIA DO GELO"}, {"key":"sectorId","value":"301"}, {"key":"region","value":"RR"}]}
反序列化的消息具有不同的数据类型，然后您尝试进行类型转换。
LinkedMultiValueMap<Integer, Object> linkedHashMap = (LinkedMultiValueMap<Integer, Object>)(new Gson().fromJson(json,LinkedMultiValueMap.class));
for(Entry<Integer, List<Object>> entry: linkedHashMap.entrySet()){
System.out.println(entry.getValue().get(0).getClass());
}
这段代码会打印class com.google.gson.internal.LinkedTreeMap，这清楚地表明列表中的数据类型是别的东西，那不是 CSVModelAttributes，实际上，它是TreeMap.
你应该定义一个这样的模型
public class CsvModels extends LinkedMultiValueMap<Integer, CSVModelAttributes> {}
用法：
String json =
"{0=[{\"key\":\"customerId\",\"value\":\"4891\"}, {\"key\":\"companyName\",\"value\":\"GIOVANE FERREIRA\"}, {\"key\":\"place\",\"value\":\"AV AV TEPEQUEM SN\"}, {\"key\":\"neighborhood\",\"value\":\"CENTRO\"}, {\"key\":\"city\",\"value\":\"AMAJARI\"}, {\"key\":\"a\",\"value\":\"RR\"}, {\"key\":\"postalCode\",\"value\":\"69300000\"}, {\"key\":\"c\",\"value\":\"ISENTO\"}, {\"key\":\"tradeName\",\"value\":\"CIA DO GELO\"}, {\"key\":\"sectorId\",\"value\":\"301\"}, {\"key\":\"region\",\"value\":\"RR\"}]}";
CsvModels models = (new Gson().fromJson(json, CsvModels.class));
for (Entry<Integer, List<CSVModelAttributes>> entry : models.entrySet()) {
System.out.println(entry.getKey());
for (CSVModelAttributes attributes : entry.getValue()) {
System.out.println("\t" + attributes);
}
}
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