struts2.1.6 Exception 08

ExceptionHandling

1. 在Actoin中進行異常映射

2. 在package中進行全局異常映射

3. 使用繼承共用異常映射

4. Struts2中異常處理由攔截器實現（觀察struts-default.xml）

a) 實際上Struts2的大多數功能都由攔截器實現

<exception-mapping result="error" exception="java.sql.SQLException"/>
            <result name="error">/error.jsp</result>

public List<Category> list()throws SQLException {
        Connection conn = DB.createConnection();
        String sql = "select * from _category_";  //測試聲明事異常 表名錯
        PreparedStatement pstm = DB.prepare(conn, sql);
        List<Category> list = new ArrayList<Category>();
        try {
            ResultSet rs = pstm.executeQuery();
            Category c = null;
            while(rs.next()) {
                c = new Category();
                c.setId(rs.getInt("id"));
                c.setName(rs.getString("name"));
                c.setDescription(rs.getString("description"));
                list.add(c);
            }
        } catch (SQLException e) {
            e.printStackTrace();
            throw(e);
        }
        DB.close(pstm);
        DB.close(conn);
        return list;
    }

public String list() throws Exception {
        categories = categoryService.list();
        return SUCCESS;
    }

<package name="front" namespace="/" extends="struts-default" >
       <action name="Category_list" class="com.gz.bbs2011.action.CategoryAction" method="list">
               <result>/admin/Category_list.jsp</result>
               <exception-mapping result="error" exception="java.sql.SQLException"/>
               <result name="error">/error.jsp</result>
       </action>
    </package>

<global-exception-mappings>
            <exception-mapping result="exception_handle" exception="Exception"></exception-mapping>
        </global-exception-mappings>

映射所有異常

常用方式
<constant name="struts.devMode" value="true"/>
    <package name="bbs2011_default" extends="struts-default">
        <global-results>
            <result name="error">/error.jsp</result>
        </global-results>
         <global-exception-mappings>
            <exception-mapping result="error" exception="java.lang.Exception"/>
        </global-exception-mappings>
    </package>

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
    "http://struts.apache.org/dtds/struts-2.0.dtd">

<struts>
    <constant name="struts.devMode" value="true"/>
    <package name="bbs2011_default" extends="struts-default">
        <global-results>
            <result name="error">/error.jsp</result>
        </global-results>
         <global-exception-mappings>
            <exception-mapping result="error" exception="java.lang.Exception"/>
        </global-exception-mappings>
    </package>


    <package name="admin" namespace="/admin" extends="struts-default" >


        <action name="index">
            <result>/admin/index.html</result>
        </action>


       <action name="*_*" class="com.gz.bbs2011.action.{1}Action" method="{2}">
            <result>/admin/{1}_{2}.jsp</result>
            <result name="input">/admin/{1}_{2}.jsp</result>

       </action>
       <!--
       <action name="category" class="com.gz.bbs2011.action.{1}Action">
        <result name="add_input">/admin/Category_add_input.jsp</result>
        <result name="update_input">/admin/Category_update_input.jsp</result>
       </action>
        -->
    </package>

    <package name="front" namespace="/" extends="bbs2011_default" >
       <action name="Category_list" class="com.gz.bbs2011.action.CategoryAction" method="list">
            <result>/admin/Category_list.jsp</result>
   <!--          <exception-mapping result="error" exception="java.sql.SQLException"/>
            <result name="error">/error.jsp</result> -->
       </action>
    </package>


</struts>

        <default-action-ref name="Category_list"/>
       <action name="*_*" class="com.gz.bbs2011.action.{1}Action" method="{2}">
            <result>/admin/{1}_{2}.jsp</result>
            <result name="input">/admin/{1}_{2}.jsp</result>
       </action>


<default-action-ref name="Category_list"/>  如果裏面action裏面有class不可執行 不能執行

action  (慎用此方法，儘量用其他方式解決)



解決默認執行方法如下
web.xml
<welcome-file>index</welcome-file>
struts.xml
  <package name="front" namespace="/" extends="bbs2011_default" >


        <default-action-ref name="Category_list"/>   <!-- bug -->

       <action name="index" class="com.gz.bbs2011.action.CategoryAction" method="list">


    <result>/admin/Category_list.jsp</result>
  </action>
</package>