我正在尝试从我正在解析的属性文件中创建treetable，并且我不断使用下面的代码获取错误“无法实例化类”。我不确定为什么它会抛出这个例外。
for(Map.Entry<Object, Object> prop : props.entrySet()) {
String key = ((String)prop.getKey()).replace("_", " ");
String value = (String)prop.getValue();
String[] parts = key.split("\\.");
if(parts.length > 4) {
boolean topLevelExists = false;
// if there are already child nodes
if(root.getChildCount() > 0) {
for(TreeNode n : root.getChildren()) {
System.out.println("n = "+n);
System.out.println("n.data = "+((Menu)n.getData()).getName());
System.out.println("n.getType = "+n.getType());
if(n.getType().equals(parts[2])) {
System.out.println("they equal");
topLevelExists = true;
if(topLevelExists == true) {
System.out.println("topLevelExists");
TreeNode node = new DefaultTreeNode(parts[2], new Menu(parts[2], value), n);
}
} else {
TreeNode node = new DefaultTreeNode(parts[2], new Menu(parts[2], value), root); // FAILS ON THIS LINE WITH THE EXCEPTION BELOW
}
}
// else we are creating the first node
} else {
TreeNode node = new DefaultTreeNode(parts[2], new Menu(parts[2], value), root);
}
}
}
Menu.java
public class Menu {
private String name;
private String path;
public Menu(String name, String path) {
this.name = name;
this.path = path;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPath() {
return path;
}
public void setPath(String path) {
this.path = path;
}
}
抛出异常
com.sun.faces.mgbean.ManagedBeanCreationException: Cant instantiate class: edu.mayo.ccs.alliance.menu.backing.MenuBacking.
at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:193)
at com.sun.faces.mgbean.BeanBuilder.build(BeanBuilder.java:102)
at com.sun.faces.mgbean.BeanManager.createAndPush(BeanManager.java:409)
at com.sun.faces.mgbean.BeanManager.create(BeanManager.java:269)
at com.sun.faces.el.ManagedBeanELResolver.resolveBean(ManagedBeanELResolver.java:244)
at com.sun.faces.el.ManagedBeanELResolver.getValue(ManagedBeanELResolver.java:116)
at com.sun.faces.el.DemuxCompositeELResolver._getValue(DemuxCompositeELResolver.java:176)
at com.sun.faces.el.DemuxCompositeELResolver.getValue(DemuxCompositeELResolver.java:203)
at org.apache.el.parser.AstIdentifier.getValue(AstIdentifier.java:69)
at org.apache.el.parser.AstValue.getValue(AstValue.java:112)
at org.apache.el.ValueExpressionImpl.getValue(ValueExpressionImpl.java:186)
at com.sun.faces.facelets.el.TagValueExpression.getValue(TagValueExpression.java:109)
at javax.faces.component.ComponentStateHelper.eval(ComponentStateHelper.java:193)
at org.primefaces.component.api.UITree.getValue(UITree.java:99)
at org.primefaces.component.treetable.TreeTableRenderer.encodeTbody(TreeTableRenderer.java:260)
at org.primefaces.component.treetable.TreeTableRenderer.encodeRegularMarkup(TreeTableRenderer.java:208)
at org.primefaces.component.treetable.TreeTableRenderer.encodeMarkup(TreeTableRenderer.java:132)
at org.primefaces.component.treetable.TreeTableRenderer.encodeEnd(TreeTableRenderer.java:88)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:884)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1681)
at javax.faces.render.Renderer.encodeChildren(Renderer.java:168)
at javax.faces.component.UIComponentBase.encodeChildren(UIComponentBase.java:854)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1674)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1677)
at org.primefaces.component.accordionpanel.AccordionPanelRenderer.encodeTab(AccordionPanelRenderer.java:218)
at org.primefaces.component.accordionpanel.AccordionPanelRenderer.encodeTabs(AccordionPanelRenderer.java:147)
at org.primefaces.component.accordionpanel.AccordionPanelRenderer.encodeMarkup(AccordionPanelRenderer.java:91)
at org.primefaces.component.accordionpanel.AccordionPanelRenderer.encodeEnd(AccordionPanelRenderer.java:71)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:884)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1681)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1677)
at org.primefaces.component.tabview.TabViewRenderer.encodeTabContent(TabViewRenderer.java:279)
at org.primefaces.component.tabview.TabViewRenderer.encodeContents(TabViewRenderer.java:237)
at org.primefaces.component.tabview.TabViewRenderer.encodeMarkup(TabViewRenderer.java:128)
at org.primefaces.component.tabview.TabViewRenderer.encodeEnd(TabViewRenderer.java:69)
at javax.faces.component.UIComponentBase.encodeEnd(UIComponentBase.java:884)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1681)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1677)
at javax.faces.component.UIComponent.encodeAll(UIComponent.java:1677)
at com.sun.faces.application.view.FaceletViewHandlingStrategy.renderView(FaceletViewHandlingStrategy.java:399)
at com.sun.faces.application.view.MultiViewHandler.renderView(MultiViewHandler.java:131)
at com.sun.faces.lifecycle.RenderResponsePhase.execute(RenderResponsePhase.java:121)
at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
at com.sun.faces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:139)
at javax.faces.webapp.FacesServlet.service(FacesServlet.java:509)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.primefaces.webapp.filter.FileUploadFilter.doFilter(FileUploadFilter.java:79)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at edu.mayo.ccs.alliance.util.BrowserNotSupportedFilter.doFilter(BrowserNotSupportedFilter.java:151)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:235)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:563)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:127)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at edu.mayo.ccs.ctsu.sso.CustomAuthenticator.invoke(CustomAuthenticator.java:42)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:859)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:602)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:489)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.util.ConcurrentModificationException
at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
at java.util.AbstractList$Itr.next(AbstractList.java:343)
at edu.mayo.ccs.alliance.menu.backing.MenuBacking.parseMenu(MenuBacking.java:151)
at edu.mayo.ccs.alliance.menu.backing.MenuBacking.<init>(MenuBacking.java:96)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:513)
at java.lang.Class.newInstance0(Class.java:355)
at java.lang.Class.newInstance(Class.java:308)
at com.sun.faces.mgbean.BeanBuilder.newBeanInstance(BeanBuilder.java:188)
... 64 more
答案 0 :(得分：2)
到目前为止，当你还在迭代它时，你正在修改root。
for (TreeNode n : root.getChildren()) {
// ...
TreeNode node = new DefaultTreeNode(parts[2], new Menu(parts[2], value), root); // FAILS ON THIS LINE WITH THE EXCEPTION BELOW
// ...
}
new DefaultTreeNode会将new Menu添加为给定root的子项。但是，这将导致迭代失败，因为后备集合已同时被修改。这就是ConcurrentModificationException试图告诉你的全部内容。
您需要相应地重写代码，以便在迭代new DefaultTreeMode时未创建root root子项。我基本上可以看到两种方法来解决这个问题：重新设计代码，这样你根本不需要遍历root，或者在某些List或Map中收集新的孩子然后将它们添加到root。具体的功能要求并不完全清楚，所以我不能建议哪一个是正确的解决方案。