java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast

Question

javascript

$.ajax({ 
 headers : { 
 'Accept' : 'application/json' , 
 'Content-Type' : 'application/json' 
 },
 url : "/realgrid/product/addOd.do",
 type : "post",
 data : JSON.stringify(JsonOrderDetailValues),
 dataType : "json",
 success : function(data){
 var json = eval(data);
 if (json.result == 1) {
 alert("insert.");
 }else if(json.result == 2){
 alert("update.")
 }else {
 alert("error.");
 }
 },
 error : function(request,status,error){
 alert("code:"+request.status+"\n"+"error:"+error);
 }
});

console.log(JsonOrderDetailValues)

[Object, Object, Object, Object]
0: Object
categoryCode: "AC-MV"
categoryName: undefined
costPrice: 168050
date: undefined
modelCode: "YP-GB70"
modelName: undefined
no: 1
number: "201309120932"
total: 88
totalPrice: 14788400
typeCode: "AV"
typeName: undefined
unitPrice: 294500
__proto__: Object
1: Object
2: Object
3: Object

java spring Controller

 @RequestMapping (value="/addOd.do",method=RequestMethod.POST)
public ModelAndView addOdMaster(@RequestBody List<OrderDetails> od){
 //java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast
 System.out.println(od.get(0).getNumber());
 Map<String, Integer> result = new HashMap<String,Integer>();
 result.put("result", 0);
 return new ModelAndView("jsonView",result);
}

vo

public class OrderDetails {
private String number;
private int no;
private String typeCode;
private String categoryCode;
private String modelCode;
private int total;
private int costPrice;
private int unitPrice;
private int totalPrice;
public int getTotalPrice() {
 return totalPrice;
}
public void setTotalPrice(int totalPrice) {
 this.totalPrice = totalPrice;
}
public String getNumber() {
 return number;
}
public void setNumber(String number) {
 this.number = number;
}
public int getNo() {
 return no;
}
public void setNo(int no) {
 this.no = no;
}
public String getTypeCode() {
 return typeCode;
}
public void setTypeCode(String typeCode) {
 this.typeCode = typeCode;
}
public String getCategoryCode() {
 return categoryCode;
}
public void setCategoryCode(String categoryCode) {
 this.categoryCode = categoryCode;
}
public String getModelCode() {
 return modelCode;
}
public void setModelCode(String modelCode) {
 this.modelCode = modelCode;
}
public int getTotal() {
 return total;
}
public void setTotal(int total) {
 this.total = total;
}
public int getCostPrice() {
 return costPrice;
}
public void setCostPrice(int costPrice) {
 this.costPrice = costPrice;
}
public int getUnitPrice() {
 return unitPrice;
}
public void setUnitPrice(int unitPrice) {
 this.unitPrice = unitPrice;
}
}

error message

FATAL: Servlet.service() for servlet [dispatcher] in context with path [/realgrid] threw exception [Request processing failed; nested exception is java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.realgrid.productControl.model.OrderDetails] with root cause
java.lang.ClassCastException: java.util.LinkedHashMap cannot be cast to com.realgrid.productControl.model.OrderDetails
 at com.realgrid.productControl.controller.ProductControlController.addOdMaster(ProductControlController.java:181)
 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.invoke(InvocableHandlerMethod.java:213)
 at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:126)
 at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:96)
 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:617)
 at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:578)
 at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:80)
 at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:923)
 at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:852)
 at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:882)
 at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:789)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
 at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:88)
 at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:76)
 at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
 at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
 at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
 at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:164)
 at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:462)
 at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
 at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
 at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:562)
 at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
 at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:395)
 at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:250)
 at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
 at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
 at java.lang.Thread.run(Unknown Source)

Why not?

• Sotirios Delimanolis: What Spring version are you using?

Answer 1

In older versions of Spring, Spring couldn't (or rather wouldn't) determine that

@RequestBody List<OrderDetails> od

had a generic type of OrderDetails and therefore Jackson (the JSON deserialiser) would use LinkedHashMap as a default type. Type safety would break as in your case because all this whole request handling invocation (@RequestMapping method and its arguments) is done through reflection.

The solution for those versions is to create your own type

public class OrderDetailsList extends ArrayList<OrderDetails> {}

and use that as a parameter

@RequestBody OrderDetailsList od

(Or upgrade to Spring 4.)

• vs4vijay: Or you could use od.get(0).get("number")
• Sotirios Delimanolis: @vs4vijay Actually they couldn't. get(0), because of the generic type argument, returns a OrderDetails and that does not have a get(String) method. The actual object returned does, but the ClassCastException rightfully breaks the operation as soon as possible.