struts中異常處理
RuntimeException和Exception的區別------
Exception需要顯式捕獲
Struts中的異常處理和國際化訊息文字密切聯絡
Struts中處理異常的三種方式：
1.程式設計式異常
在Action中捕獲異常
|
public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) throws Exception { UserForm formbean = (UserForm)form; UserManager userManager = new UserManagerImpl(); try { userManager.login(formbean.getUsername(), formbean.getPassword()); } catch (Exception e) { e.printStackTrace(); //建立國際化訊息文字 ActionMessages errors = new ActionMessages(); ActionMessage error = new ActionMessage("errors.detail",e.getMessage()); errors.add("user.exception", error); //傳遞國際化訊息文字 this.saveErrors(request, errors); return mapping.findForward("error"); } return mapping.findForward("success"); } |
頁面顯示異常資訊
|
<body> <html:messages id="msg" message="true"> ${msg} </html:messages> <html:errors/> </body> |
注意：如果處理的是messages物件，需要新增屬性message="true"
2.
只需要在struts配置檔案中配置
|
<action path="/login" type="cn.yjj.test.web.UserAction" name="userForm" scope="request" input="/login_error.jsp" > <exception key="errors.detail" type="java.lang.RuntimeException" path="/login_error.jsp"/> <forward name="success" path="/login_success.jsp"/> <forward name="error" path="/login_error.jsp"/> </action> |
Key----國際化訊息文字中的key
Type----異常類的完整路徑
Path-----轉向路徑優先順序>input屬性
3.個性化異常處理(解決多個國際化文字和填充符的問題)
需要了解struts中自動處理異常的機制
異常類
|
package cn.yjj.test.base; publicclass SystemException extends RuntimeException { private String errorCode; private Object[] params; public SystemException(String message){ super(message); } public SystemException(String message, String errorCode){ this(message, errorCode, null); } public SystemException(String message, String errorCode, Object param){ this(message, errorCode, new Object[]{param}); } public SystemException(String message, String errorCode, Object[] params){ super(message); this.errorCode = errorCode; this.params = params; } public String getErrorCode() { returnerrorCode; } public Object[] getParams() { returnparams; } } |
異常處理類
|
package cn.yjj.test.base; import javax.servlet.ServletException; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import org.apache.struts.Globals; import org.apache.struts.action.ActionForm; import org.apache.struts.action.ActionForward; import org.apache.struts.action.ActionMapping; import org.apache.struts.action.ActionMessage; import org.apache.struts.action.ExceptionHandler; import org.apache.struts.config.ExceptionConfig; import org.apache.struts.util.ModuleException; publicclass SystemExceptionHandler extends ExceptionHandler { public ActionForward execute( Exception ex, ExceptionConfig ae, ActionMapping mapping, ActionForm formInstance, HttpServletRequest request, HttpServletResponse response) throws ServletException { if(!(ex instanceof SystemException)){ returnsuper.execute(ex, ae, mapping, formInstance, request, response); } ActionForward forward = null; ActionMessage error = null; String property = null; // Build the forward from the exception mapping if it exists // or from the form input if (ae.getPath() != null) { forward = new ActionForward(ae.getPath()); } else { forward = mapping.getInputForward(); } // Figure out the error if (ex instanceof ModuleException) { error = ((ModuleException) ex).getActionMessage(); property = ((ModuleException) ex).getProperty(); } else { SystemException se = (SystemException)ex; String errorCode = se.getErrorCode(); Object[] params = se.getParams(); if(errorCode==null){ error = new ActionMessage(ae.getKey(), se.getMessage()); }else{ error = new ActionMessage(errorCode, params); } property = error.getKey(); } this.logException(ex); // Store the exception request.setAttribute(Globals.EXCEPTION_KEY, ex); this.storeException(request, property, error, forward, ae.getScope()); return forward; } } |
配置檔案
|
<action path="/login" type="cn.yjj.test.web.UserAction" name="userForm" scope="request" input="/login_error.jsp" > <exception key="errors.detail" type="cn.yjj.test.base.SystemException" path="/login_error.jsp" handler="cn.yjj.test.base.SystemExceptionHandler"/> <forward name="success" path="/login_success.jsp"/> <forward name="error" path="/login_error.jsp"/> </action> |
1、程式設計式異常
* 截獲異常
* 建立相應的異常訊息
* 傳遞異常訊息
* 轉向相應的頁面處理異常
2、宣告式異常（自動處理的異常）
* 在struts-config.xml檔案中配置<exeception/>標籤
* 理解區域性和全域性exception
* 注意區域性<exception/>標籤需要配置到<forward/>標籤的前面，詳見dtd中的約束
<exeception/>標籤中的屬性說明：
* key：指異常資訊對應的國際化訊息文字，這個key值需要在國際化資原始檔中定義
* type: 處理那種異常
* path: 定義一但出現異常，需要轉向那個頁面，如果不定義path，
預設情況下將使用<action>標籤中input屬性對應的頁面
* scope：可以取值request和session，預設為request
* handler：異常的處理類，struts預設採用org.apache.struts.action.ExceptionHandler，
如果做個性化的異常處理可以繼承此類覆寫相應的方法