我将此代码作为 Java 应用程序在 Tomcat 服务器上运行。
if(levelMap.get(bssid_a) == null)
continue;
ArrayList<String> levels_a = new ArrayList<String>();
levels_a = (ArrayList<String>)levelMap.get(bssid_a);
其中levelMap是一个hashmap,定义为:
HashMap<String, ArrayList<String>> levelMap
我收到此错误:
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to java.util.ArrayList
相同的代码在我的 Android 应用程序中运行,所以我不确定为什么会收到此错误。
原始函数(没有类型转换,但给了我同样的错误):
public EDistance[] getLocation(HashMap<String, ArrayList<String>> levelMap) {
HashMap<String, CrossProduct> crossProductList_local = new HashMap<String, CrossProduct>();
LinkedHashSet<String> localList = (LinkedHashSet<String>) globalList.clone();
Iterator<String> cpItera = localList.iterator();
long time1 = System.currentTimeMillis();
// Iterator<String> levelIter = levelMap.keySet().iterator();
// try {
while (cpItera.hasNext()) {
String ssids[] = cpItera.next().split(",");
String bssid_a = ssids[0];
if(levelMap.get(bssid_a) == null)
continue;
//ArrayList<String> levels_a = new ArrayList<String>();
ArrayList<String> levels_a = levelMap.get(bssid_a);
double meanA = mean(levels_a, sampleSize, defaultLevel);
// Iterator<String> cpIterb = localList.iterator();
//
// while(cpIterb.hasNext())
// {
String bssid_b = ssids[1];
// if(bssid_a.equals(bssid_b))
// continue;
if(levelMap.get(bssid_b) == null)
continue;
//ArrayList<String> levels_b = new ArrayList<String>();
ArrayList<String> levels_b = levelMap.get(bssid_b);
double meanB = mean(levels_b, sampleSize, defaultLevel);
............
这是堆栈跟踪:
SEVERE: Failed to invoke method distance in class com.fingerprint.core.Calculate: [Ljava.lang.Object; cannot be cast to java.util.ArrayList
org.apache.xmlrpc.common.XmlRpcInvocationException: Failed to invoke method distance in class com.fingerprint.core.Calculate: [Ljava.lang.Object; cannot be cast to java.util.ArrayList
at org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.invoke(ReflectiveXmlRpcHandler.java:129)
at org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.execute(ReflectiveXmlRpcHandler.java:106)
at org.apache.xmlrpc.server.XmlRpcServerWorker.execute(XmlRpcServerWorker.java:46)
at org.apache.xmlrpc.server.XmlRpcServer.execute(XmlRpcServer.java:86)
at org.apache.xmlrpc.server.XmlRpcStreamServer.execute(XmlRpcStreamServer.java:200)
at org.apache.xmlrpc.webserver.XmlRpcServletServer.execute(XmlRpcServletServer.java:112)
at org.apache.xmlrpc.webserver.XmlRpcServlet.doPost(XmlRpcServlet.java:196)
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:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1001)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to java.util.ArrayList
at com.fingerprint.location.HyperbolicEuclideanDistance.getLocation(HyperbolicEuclideanDistance.java:235)
at com.fingerprint.core.Calculate.distance(Calculate.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.apache.xmlrpc.server.ReflectiveXmlRpcHandler.invoke(ReflectiveXmlRpcHandler.java:115)
... 24 more
Caused by:
java.lang.ClassCastException: [Ljava.lang.Object; cannot be cast to java.util.ArrayList
at com.fingerprint.location.HyperbolicEuclideanDistance.getLocation(HyperbolicEuclideanDistance.java:235)
at com.fingerprint.core.Calculate.distance(Calculate.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.apache.xmlrpc.server.ReflectiveXmlRpcHandler.invoke(ReflectiveXmlRpcHandler.java:115)
at org.apache.xmlrpc.server.ReflectiveXmlRpcHandler.execute(ReflectiveXmlRpcHandler.java:106)
at org.apache.xmlrpc.server.XmlRpcServerWorker.execute(XmlRpcServerWorker.java:46)
at org.apache.xmlrpc.server.XmlRpcServer.execute(XmlRpcServer.java:86)
at org.apache.xmlrpc.server.XmlRpcStreamServer.execute(XmlRpcStreamServer.java:200)
at org.apache.xmlrpc.webserver.XmlRpcServletServer.execute(XmlRpcServletServer.java:112)
at org.apache.xmlrpc.webserver.XmlRpcServlet.doPost(XmlRpcServlet.java:196)
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:305)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)
at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1001)
at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:579)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)
at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
at java.lang.Thread.run(Unknown Source)
调用XMlRPC方法的代码:
public String getLocationXMLRPC(HashMap<String, ArrayList<String>> levelMap, String mapFile) {
try {
XMLRPCClient client = new XMLRPCClient("http://172.28.184.222:8080/LocationService/xmlrpc");
Object[] params = new Object[]{levelMap, mapFile};
//EDistance retura[] = (EDistance[]) client.callEx("Calculate.distance", params);
String result = (String) client.callEx("Calculate.distance", params);
return result;
} catch (XMLRPCException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
调用错误函数的XMLRPC方法:
public String distance(HashMap<String, ArrayList<String>> levelMap, String mapFile)
{
if(dist == null){
dist = new HyperbolicEuclideanDistance(mapFile, 3, -130,
false, "fake.txt");
System.out.println("New Class created!");
}
EDistance[] result = dist.getLocation(levelMap);
StringBuilder build = new StringBuilder();
for (int j = 0; j < result.length; j++) {
if (result[j] != null)
build.append(j + ") " + result[j] + "\n");
}
return build.toString();
}
调用服务器的代码:
public String getLocationXMLRPC(HashMap<String, ArrayList<String>> levelMap, String mapFile) {
try {
XMLRPCClient client = new XMLRPCClient("http://172.28.184.222:8080/LocationService/xmlrpc");
String result = (String) client.call("Calculate.distance", levelMap, mapFile);
return result;
} catch (XMLRPCException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
最佳答案
根据ws-xmlrpc XMLRPC Data-Types一个HashMap<String, ArrayList<String>>
不是直接支持的参数类型。
从您发布的异常堆栈跟踪中可以看到 HashMap<String, Object>
沿着线路到达 XMLRPC 服务器。这是显而易见的,因为服务器需要调用 distance
使用Java反射的方法。这样做的话,如果参数至少不是 HashMap,就会发生异常。相反,当从该映射检索对象时,跟踪中会发生异常。从 HashMap<String, ArrayList<String>>
检索和分配元素时,运行时会进行不可见的类型检查。 ,并且该检查失败,但您有异常(exception)。
因此,XMLRPC 库传递参数可能存在编码问题。所以,如Map<String, List<String>>
根据上述文档应该是有效的参数类型,但尝试更改 distance
方法及其被调用者参数,然后重试。
如果这也失败,请考虑以另一个更平坦和简单的结构传递参数。
关于java - 无法将 HashMap 返回的对象转换为 Arraylist,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/11483772/