009 - 声明式异常
1. 声明式异常

?

?//struts.xml

<struts>
??????? <constant name="struts.devMode" value="true"></constant>

??????? <global-results>
??? ?????????? <result name="error">/error.jsp</result>
??? ??? </global-results>
?????
??????? <global-exception-mappings>
??? ????????? <exception-mapping result="error" exception="java.lang.Exception"></exception-mapping>
??????? </global-exception-mappings>
??????
?????
???????<package name="admin" namespace="/admin" extends="struts-default" >
?????
????????????? ?<action name="userList" exception="java.sql.SQLException" />??
?????????????????????????? <result name="error">/error.jsp</result> -->
???????????? ?</action>

??? </package>
????????
</struts>

?

?

?

?//CategoryAction

public class CategoryAction extends ActionSupport {
???????? private?User user;

?

????????//Action接到user.list()抛来的异常,并把它抛出struts2,struts2根据struts.xml里的配置找到相应页面
???????? public String list() ?throws Exception {??

???????????????????categories =?user.list();
?????????????????? return SUCCESS;
???????? }
?
}

?

?

?//UserService

public class UserService {

?public List<User> list() throws SQLException {
??????? Connection conn = DB.createConn();
????????String sql = "select * from t_user_";????????//故意写错，产生java.sql.Exception,抛给了UserAction
????????PreparedStatement ps = DB.prepare(conn, sql);
?????? ?List<User> users= new ArrayList<User>();
??????? try {
?????????????? ResultSet rs = ps.executeQuery();
?????????????? User u= null;
?????????????? while(rs.next()) {
???????????????????? u = new User();
??????????????????? ?u.setId(rs.getInt("id"));
???????????????????? u.setName(rs.getString("name"));
???????????????????? users.add(u);
???????????????}
??????? } catch (SQLException e) {
?????????????????? ?e.printStackTrace();
?????????????????? ?throw(e);
??????? }
?????? DB.close(ps);
?????? DB.close(conn);
?????? return categories;
?}

?
}