在service方法里 throw抛出一个异常, 然后再方法声明上加上throws:
public List<Category> list() throws SQLException{ Connection conn=DB.createConn(); String sql = "select * from _category"; PreparedStatement ps = DB.prepare(conn, sql); List<Category> categories = new ArrayList<Category>(); try { ResultSet rs=ps.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")); categories.add(c); } } catch (SQLException e) { e.printStackTrace(); throw(e); } DB.close(ps); DB.close(conn); return categories; }
在调用list方法的action里 throws, 这样就不用try catch而是由struts2处理:
public String list() throws Exception{ categories=categoryService.list(); return SUCCESS; }
struts.xml里如何配置?
<package name="admin" namespace="/admin" extends="struts-default" > <default-action-ref name="index"/> <action name="index"> <result>/admin/index.html</result> </action> <action name="*_*" class="com.bjsxt.bbs2009.action.{1}Action" method="{2}"> <result>/admin/{1}_{2}.jsp</result> <result name="input">/admin/{1}_{2}.jsp</result>
<exception-mapping result="error" exception="java.sql.SQLException"/> <result name="error">/error.jsp</result>
<result name="exception_handle">/admin/exception.jsp</result> </action> </package>
service里的sql语句改成错误的, 这样在调用页面的时候, 就会显示error.jsp.
下面是异常处理最常用的方法:
1. 配置新的package, global results, global-exception-mappings, 自己的action的包继承异常包即可.
原理:::拦截器
<package name="bbs2009_default" extends="struts-default"> <global-results> <result name="error">/error.jsp</result> </global-results> <global-exception-mappings> <exception-mapping result="error" exception="Exception"></exception-mapping> </global-exception-mappings> </package> <package name="admin" namespace="/admin" extends="bbs2009_default" > <default-action-ref name="index"/> <action name="index"> <result>/admin/index.html</result> </action> <action name="*_*" class="com.bjsxt.bbs2009.action.{1}Action" method="{2}"> <result>/admin/{1}_{2}.jsp</result> <result name="input">/admin/{1}_{2}.jsp</result> <!--<exception-mapping result="error" exception="java.sql.SQLException"/> <result name="error">/error.jsp</result>--> <result name="exception_handle">/admin/exception.jsp</result> </action> </package>