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?

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.)