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    java開發(fā)出錯筆記.doc

    java 開發(fā)出錯筆記 ---powered by jgao

    1.

    出錯描述: struts 開發(fā)中拋出異常java.lang.IllegalArgumentException No destination bean specified

    原因: 前面?zhèn)鬟f過來的表單于后面要顯示的表單不一致,或著說前面沒綁定表單,而你卻使用了如下語句:???

    // 語句的作用是初始化UserFormUserForm的值都為空?

    User user = new User();????

    UserForm userForm = (UserForm)form;???? BeanUtils.copyProperties(userForm,user);

    處理: 在相對應的action里面加入attributename參數(shù)綁定到對應的表單就行了

    ?

    2.

    出錯描述: struts 開發(fā)中拋出異常javax.servlet.ServletException: Cannot retrieve definition for form bean null

    原因: 你的頁面想跟表單綁定而你的action卻沒有綁定到表單,所以找不到相應得表單

    處理: 在相對應的action里面加入attributename參數(shù)綁定到對應的表單就行了

    3.

    出錯描述: struts 開發(fā)中 The requested resource (/jgaoForum/user/userList.do) is not available.

    原因: 如果你確定你的路徑絕對正確,那么看看你的web.xml是否放在webinf目錄下,在不行那么你的web.xml配置正確嗎?

    ??? < servlet-name > action </ servlet-name >

    ??? < servlet-class > org.apache.struts.action.ActionServlet </ servlet-class >

    ??? < init-param >

    ????? < param-name > config </ param-name >

    ?? // 這里路徑對嗎?

    ?? < param-value > /WEB-INF/strutsconfig/struts-config.xml </ param-value >

    ??? </ init-param >

    ? < servlet-mapping >

    ??? < servlet-name > action </ servlet-name >

    ??? < url-pattern > *.do </ url-pattern > // 這里是 *.do 嗎?

    ? </ servlet-mapping >

    處理: 再不行我也沒辦法了

    4.

    出錯描述: jsp+mysql 中文亂碼 .

    原因: 編碼不匹配

    處理:

    1. 首先建庫和建表的時候在后面加上這句ENGINE=InnoDB DEFAULT CHARSET=gb2312

    如果mysql版本有支持gb2312的話那么可以在安裝的時候選擇gb2312,默認是lant1,這樣建庫和建表的時候就不用加上ENGINE=InnoDB DEFAULT CHARSET=gb2312

    2. 數(shù)據(jù)庫連接url要如下形式,后面要加上編碼方式

    a> 直接在java代碼里面

    jdbc:mysql://localhost:3306/jgaooa?useUnicode=true&characterEncoding=gb2312

    b> 放在配置文件(配置文件最好是xml,并且xml文件頭也要有編碼方式<?xml version="1.0" encoding="GB2312"?>

    jdbc:mysql://localhost:3306/jgaooa?useUnicode=true&amp;characterEncoding=gb2312

    3. 每個jsp文件的文件頭要加上

    <%@ page contentType="text/html;charset=gb2312" %> 不然頁面的中文會顯示亂碼

    4. 頁面數(shù)據(jù)之間的傳輸requestresponse要加上編碼,最好的方式就是通過filter過濾器

    過濾器代碼如下:該代碼由javastudio獲得

    package org.jgao.soft;

    ?

    import java.io.IOException;

    ?

    import javax.servlet.Filter;

    import javax.servlet.FilterChain;

    import javax.servlet.FilterConfig;

    import javax.servlet.ServletException;

    import javax.servlet.ServletRequest;

    import javax.servlet.ServletResponse;

    ?

    /**

    ?* 中文過濾器

    ?*/

    public class SetCharacterEncodingFilter implements Filter {

    ?

    ??? // ----------------------------------------------------- Instance Variables

    ?

    ??? /**

    ??? ?* The default character encoding to set for requests that pass through this

    ??? ?* filter.

    ??? ?*/

    ??? protected String encoding = null;

    ?

    ??? /**

    ??? ?* The filter configuration object we are associated with. If this value is

    ??? ?* null, this filter instance is not currently configured.

    ??? ?*/

    ??? protected FilterConfig filterConfig = null;

    ?

    ??? /**

    ??? ?* Should a character encoding specified by the client be ignored?

    ??? ?*/

    ??? protected boolean ignore = true;

    ?

    ??? // --------------------------------------------------------- Public Methods

    ?

    ??? /**

    ??? ?* Take this filter out of service.

    ??? ?*/

    ??? public void destroy() {

    ?

    ??????? this.encoding = null;

    ??????? this.filterConfig = null;

    ?

    ??? }

    ?

    ??? /**

    ??? ?* Select and set (if specified) the character encoding to be used to

    ??? ?* interpret request parameters for this request.

    ??? ?*

    ??? ?* @param request

    ??? ?*??????????? The servlet request we are processing

    ??? ?* @param result

    ??? ?*??????????? The servlet response we are creating

    ??? ?* @param chain

    ??? ?*??????????? The filter chain we are processing

    ??? ?*

    ??? ?* @exception IOException

    ??? ?*??????????????? if an input/output error occurs

    ??? ?* @exception ServletException

    ??? ?*??????????????? if a servlet error occurs

    ??? ?*/

    ??? public void doFilter(ServletRequest request, ServletResponse response,

    ??????????? FilterChain chain) throws IOException, ServletException {

    ?

    ??????? // Conditionally select and set the character encoding to be used

    ??????? if (ignore || (request.getCharacterEncoding() == null)) {

    ??????????? String encoding = selectEncoding(request);

    ??????????? if (encoding != null)

    ??????????????? request.setCharacterEncoding(encoding);

    ??????? }

    ?

    ??????? // Pass control on to the next filter

    ??????? chain.doFilter(request, response);

    ?

    ??? }

    ?

    ??? /**

    ??? ?* Place this filter into service.

    ??? ?*

    ??? ?* @param filterConfig

    ??? ?*??????????? The filter configuration object

    ??? ?*/

    ??? public void init(FilterConfig filterConfig) throws ServletException {

    ?

    ??????? this.filterConfig = filterConfig;

    ??????? this.encoding = filterConfig.getInitParameter("encoding");

    ??????? String value = filterConfig.getInitParameter("ignore");

    ??????? if (value == null)

    ??????????? this.ignore = true;

    ??????? else if (value.equalsIgnoreCase("true"))

    ??????????? this.ignore = true;

    ??????? else if (value.equalsIgnoreCase("yes"))

    ??????????? this.ignore = true;

    ??????? else

    ??????????? this.ignore = false;

    ?

    ??? }

    ?

    ??? // ------------------------------------------------------ Protected Methods

    ?

    ??? /**

    ??? ?* Select an appropriate character encoding to be used, based on the

    ??? ?* characteristics of the current request and/or filter initialization

    ??? ?* parameters. If no character encoding should be set, return

    ??? ?* <code>null</code>.

    ??? ?* <p>

    ??? ?* The default implementation unconditionally returns the value configured

    ??? ?* by the <strong>encoding</strong> initialization parameter for this

    ??? ?* filter.

    ??? ?*

    ??? ?* @param request

    ??? ?*??????????? The servlet request we are processing

    ??? ?*/

    ??? protected String selectEncoding(ServletRequest request) {

    ?

    ??????? return (this.encoding);

    ?

    ??? }

    ?

    }//

    ?

    Web.xml 配置文件如下

    <? xml version = "1.0" encoding = "UTF-8" ?>

    < web-app version = "2.4" xmlns = "http://java.sun.com/xml/ns/j2ee" xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation = "http://java.sun.com/xml/ns/j2ee

    ??? http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd" >

    ?

    ??? < filter >

    ?????? < filter-name > SetCharacterEncodingFilter </ filter-name >

    ??? ??? < filter-class > org.jgao.soft.SetCharacterEncodingFilter </ filter-class >

    ?????? < init-param >

    ?????????? < param-name > encoding </ param-name >

    ?????????? < param-value > GB2312 </ param-value >

    ?????? </ init-param >

    ??? </ filter >

    ??? < filter-mapping >

    ?????? < filter-name > SetCharacterEncodingFilter </ filter-name >

    ?????? < url-pattern > /* </ url-pattern >

    ??? </ filter-mapping >

    </ web-app >

    再不能搞定那就把 mysql 扔了

    ?

    posted on 2006-06-11 08:52 JGAO編程隨筆 閱讀(1382) 評論(0)  編輯  收藏


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