BlogJava-ply-文章分类-知识小串通

length、length()、size的区别...

ply — Fri, 02 Dec 2011 05:37:00 GMT

length是数组的属性，
length()是字符串获取长度的方法，
size是list的个数

ply 2011-12-02 13:37 发表评论

struts2 异常处理总结

ply — Fri, 02 Sep 2011 15:07:00 GMT

1---:java.lang.NoClassDefFoundError: org/apache/struts2/dojo/views/jsp/ui/HeadTag

解决办法：原因缺少了dojo的JAR包，引入即可:struts2-dojo-plugin-2.1.2.jar

The "head" tag renders required JavaScript code to configure Dojo and is required in order to use any of the tags included in the Dojo plugin.

--------------------

If you are planning to nest tags from the Dojo plugin, make sure you set parseContent="false", otherwise each request made by the inner tags will be performed twice.

2---:Unable to load configuration. -bean -jar:file:/F:/Struts2/Struts2/WebRoot/WEB-INF/lib/struts2-core- 2.1.2.jar!/struts-default.xml:46:178

Caused by: Unable to load bean: type:org.apache.struts2.dispatcher.multipart.MultiPartRequest class:org.apache.struts2.dispatcher.multipart.JakartaMultiPartRequest -bean -jar:file:/F:/Struts2/Struts2/WebRoot/WEB-INF/lib/struts2-core-2.1.2.jar!/struts-default.xml:46:178

Caused by: java.lang.NoClassDefFoundError: org/apache/commons/fileupload/RequestContext
解决办法：缺少JAR包，引入commons-fileupload-1.2.1.jar，commons-io-1.3.2.jar即可

3---:No tag "datetimepicker" defined in tag library imported with prefix "s"

原因版本问题：缺少struts-dojo-plugin JAR包，以及HTML的,中没有使用标签

If you're using Struts 2.1.x you're probablymissing the>struts-dojo-plugin. Michal's reference below applies to Struts 2.1.xonly. In the lasts versions (since 2.0.9 I guess), all AJAX are in dojo> plugin.
> > So you need toinclude <%@ taglib uri="/struts-dojo-tags" prefix="sx"%>
> > and
> >( Temp1:

Temp2:

Temp3:

Temp4:
)
> > and call :

4---:使用TILES框架

If you use the Tiles 2 plugin, check your tiles.xml file(s) to ensure they contain a DOCTYPE.

5---:struts2中不支持EL表达式

Struts2.1 tags do not allow evaluation of JSP EL within their attributes.Instead, Struts2 tags evaluate attribute values as OGNL. Allowing bothexpression languages within the same attribute opens major securityvulnerabilities.

6---文件上传过程中取不到文件名和文件类型，即都取到NULL

原因：如果页面中file的name=“a”则我们ACTION中设置String aContentType,String aFileName;(此两个其实无所谓，关键是SET方法)

setA(File file)(){}; setAContentType(String s){};setAFileName(String name){} 即格式如下：setXContentType() setXFileName().X代表你给FILE取的NAME名字

必须和它相同，固定格式

7---严重: Unable to parse request
org.apache.commons.fileupload.FileUploadBase$SizeLimitExceededException: the request was rejected because its size (8523356) exceeds the configured maximum (2097152)
at org.apache.commons.fileupload.FileUploadBase$FileItemIteratorImpl.(FileUploadBase.java:914)2008-5-27 17:46:51 com.opensymphony.xwork2.util.logging.commons.CommonsLogger warn
警告: Could not find property [struts.valueStack]
2008-5-27 17:46:51 com.opensymphony.xwork2.util.logging.commons.CommonsLogger error
严重: the request was rejected because its size (8523356) exceeds the configured maximum (2097152)
2008-5-27 17:46:51 com.opensymphony.xwork2.util.logging.commons.CommonsLogger warn
警告: Could not find property [org.apache.catalina.jsp_file]

原因：上传文件大小超过预定大小，可以在struts.properties配置文件中设置struts.multipart.maxSize=XXX（XXX为文件大小）

8---配置了文件类型限制后，当传错误类型可以拦截不让用户上传该文件，可是跳转的页面却没有跳转到input配置的错误页面，而是返回

到了success正确页面。

严重: Content-Type not allowed: filedata "upload__5b01657_11a329d4dcf__8000_00000000.tmp" text/plain
《我的打印输出DEBUG语句内容:File:null FlieName:null type:null》即拦截类型成功了
java.lang.NullPointerException
at java.io.FileInputStream.(FileInputStream.java:103)
at com.study.web.util.FileUploadUtil.uploadFile(FileUploadUtil.java:36)
at com.study.web.action.UploadFileAction.execute(UploadFileAction.java:58)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)。。。

2008-5-29 10:59:07 com.opensymphony.xwork2.util.logging.commons.CommonsLogger warn
警告: Could not find property [org.apache.catalina.jsp_file]
2008-5-29 10:59:07 com.opensymphony.xwork2.util.logging.commons.CommonsLogger warn
警告: Could not find property [struts]
2008-5-29 10:59:07 com.opensymphony.xwork2.util.logging.commons.CommonsLogger info
信息: Removing file filedata \tmp\upload__5b01657_11a329d4dcf__8000_00000000.tmp

原因及解决办法：在该文件上传Action中只配置了FileUploadInterceptor后缺少配置了defaultStack拦截器.

在ACTION中配置玩defaultStack拦截器后改错误消失。

9---struts.properties中全局配置文件大小，再使用默认FileUploadInterceptor拦截器时候能实现拦截的功能但是后台出现异常。

严重: Unable to parse request
org.apache.commons.fileupload.FileUploadBase$SizeLimitExceededException: the request was rejected because its size (380) exceeds the configured maximum (10)
at org.apache.commons.fileupload.FileUploadBase$FileItemIteratorImpl.(FileUploadBase.java:914)

原因：未知。将全局配置中的限制大小去掉，再重新在ACTION中覆盖配置FileUploadInterceptor拦截器设置大小和文件类型限制，可消除异常。

10---多文件上传中，其中一个传被限制的文件如限制aplication/msword(即.doc)文件，允许传文本文件。然而当夹杂在一起传的时候，后台能截获类型错误不可传信息，但是

实际却还是上传成功。

严重: Content-Type not allowed: filedata "upload_4d958287_11a33e76ab9__8000_00000007.tmp" application/msword
file is :\tmp\upload_4d958287_11a33e76ab9__8000_00000006.tmp fileName:project.txt fileType:text/plain
file is :\tmp\upload_4d958287_11a33e76ab9__8000_00000007.tmp fileName:application base.doc fileType:application/msword
file is :\tmp\upload_4d958287_11a33e76ab9__8000_00000008.tmp fileName:zhongqi-bug.txt fileType:text/plain

原因：忘记了继承ActionSupport类。继承后异常消失。

11--文件上传异常，不能创建File文件

Cannot create type class java.io.File from value C:\Documents and Settings\admin\桌面\OrderReporterServiceImp.java - [unknown location]

原因：忘记了在form表单里将enctype设置成文件上传格式：enctype="multipart/form-data"

12--当使用限制文件类型和大小的时候抛出空指针异常

java.lang.NullPointerExceptiondemo.struts2.action.ValidatFileUploadAction.execute(ValidatFileUploadAction.java:71)sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)原因：在ACTION中配置了fileUpload拦截器后忘记了配置默认拦截器：defautlStack。注意当ACTION中配置自己的拦截器后需要显示配置默认

拦截器defaultStack

13--在国际化时候抛空指针异常：

16:31:12,812 ERROR [jsp]:253 - Servlet.service() for servlet jsp threw exception
java.lang.NullPointerException at java.text.MessageFormat.applyPattern(MessageFormat.java:414)

at java.text.MessageFormat.(MessageFormat.java:350)
at com.opensymphony.xwork2.DefaultTextProvider.getText(DefaultTextProvider.java:70)

原因：忘记了在struts.xml中配置国际化常量，或者在struts.properties中配置全局国际化常量 struts.custom.i18n.resources=globeMessage

14-- struts action的配置文件加载失败：

Unable to load configuration. - result - file:/D:/Java/apache-tomcat-5.5.20/webapps/mysts/WEB-INF/classes/test.xml:10:26

Caused by: No result type specified for result named 'error', perhaps the parent package does not specify the result type? - result - file:/D:/Java/apache-tomcat-5.5.20/webapps/mysts/WEB-INF/classes/test.xml:10:26
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.buildResults(XmlConfigurationProvider.java:609)

原因：忘记了继承包struts-default

15-- struts action 配置文件注意事项：

1. 别忘记了继承struts-default默认配置包

2.如果配置命名空间，一定要以"/"开始，例如：namespace="/test"

3.每个模块struts action配置文件中都可以配置全局result，global-result 经测试不会冲突，STRTUS会智能寻找该Action请求的

模块STRUTS ACTION配置包

关键字: 警告: no configuration found for the specified action

警告: No configuration found for the specified action: 'ShowMessage' in namespace: ''. Form action defaulting to 'action' attribute's literal value.

解决方法：

经过测试发现，是没有正确使用tag的原因，这种情况下，正确的写法应该是，

您是否添加了action这个呢？

ply 2011-09-02 23:07 发表评论

Linux下配置免安装版Tomcat .

ply — Thu, 01 Sep 2011 15:06:00 GMT

实习过程中，需要在Linux环境下配置免安装版本的Tomcat，下面列出详细步骤，希望对大家有帮助。

一、下载免安装版Tomcat

打开Tomcat主页http://tomcat.apache.org/，下载Tomcat免安装版，我这里下载的是apache-tomcat-7.0.2.tar.gz。

二、配置Java环境变量

Java的环境变量已经在前几篇文章里有了概述，详细见：http://www.fengwenxuan.com/index.php/red-hat-enterprise-linux/238.html

三、解压Tomcat

将Tomcat解压缩到/usr/local目录下

# tar zxvf apache-tomcat-7.0.2.tar.gz

四、启动Tomcat

# cd /usr/local/apache-tomcat-7.0.2/bin

# ./startup.sh

如果启动成功，shell终端会出现如下提示：

Using CATALINA_BASE: /usr/local/apache-tomcat-7.0.2

Using CATALINA_HOME: /usr/local/apache-tomcat-7.0.2

Using CATALINA_TMPDIR: /usr/local/apache-tomcat-7.0.2/temp

Using JRE_HOME: /usr/local/jdk1.6.0_21

如果终端报错，基本上可以肯定是Jdk环境变量没有配置好，仔细在检查一下Jdk环境变量的配置

五、测试Tomcat

打开火狐浏览器，地址栏输入http://localhost:8080，回车后看到Tomcat的LOGO，表示一切正常。也可以更改Tomcat目录下的conf文件夹，里面有一个server.xml文件，修改成使用80端口，这样浏览器只要输入http://localhost/就可以直接进入你的主页了。

六、停止Tomcat

# cd /usr/local/apache-tomcat-7.0.2/bin

# ./shutdown.sh

七、设置开机自动启动Tomcat

方法一：

在/usr/local/apache-tomcat-7.0.2/bin/startup.sh 为:

JAVA_HOME=/home/fwx/jdk1.6.0_14

CLASSPATH=.:$JAVA_HOME/lib/tools.jar

PATH=$JAVA_HOME/bin:$PATH

export JAVA_HOME CLASSPATH PATH

export CATALINA_HOME=/usr/local/apache-tomcat-7.0.2
/usr/local/tomcat/bin/catalina.sh start

在/etc/rc.d/rc.local中加入:
/usr/local/apache-tomcat-7.0.2/bin/startup.sh

方法二：
1、把下面的代码保存为tomcat文件，并让它成为可执行文件 chmod 755 tomcat.
#!/bin/bash
#
# fengwx0413@163.com
# /etc/rc.d/init.d/tomcat
# init script for tomcat precesses
#
# processname: tomcat
# description: tomcat is a j2se server
# chkconfig: 2345 86 16
# description: Start up the Tomcat servlet engine.

if [ -f /etc/init.d/functions ]; then
        . /etc/init.d/functions
elif [ -f /etc/rc.d/init.d/functions ]; then
        . /etc/rc.d/init.d/functions
else
        echo -e "/atomcat: unable to locate functions lib. Cannot continue."
        exit -1
fi

RETVAL=$?
CATALINA_HOME="/usr/local/apache-tomcat-7.0.2"

case "$1" in
start)
        if [ -f $CATALINA_HOME/bin/startup.sh ];
          then
            echo $"Starting Tomcat"
            $CATALINA_HOME/bin/startup.sh
        fi
        ;;
stop)
        if [ -f $CATALINA_HOME/bin/shutdown.sh ];
          then
            echo $"Stopping Tomcat"
            $CATALINA_HOME/bin/shutdown.sh
        fi
        ;;
*)
        echo $"Usage: $0 {start|stop}"
        exit 1
        ;;
esac

exit $RETVAL

2、将tomcat文件拷贝到/etc/init.d/下，并运行：chkconfig --add tomcat

3、在apache-tomcat-7.0.2/bin/catalina.sh文件中加入以下语句：
export JAVA_HOME=/home/fwx/jdk1.6.0_14
export CATALINA_HOME=/usr/local/apache-tomcat-7.0.2

export CATALINA_BASE=/usr/local/apache-tomcat-7.0.2
export CATALINA_TMPDIR=/usr/local/apache-tomcat-7.0.2/temp

启动tomcat： service tomcat start
停止tomcat: service tomcat stop　

ply 2011-09-01 23:06 发表评论

采用过滤器解决中文乱码问题

ply — Sun, 21 Aug 2011 15:13:00 GMT

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;

public class CharacterEncodingFilter implements Filter{

    private FilterConfig config;
    private String encoding;
    private boolean enable;

    public void destroy() {

    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain filterChain) throws IOException, ServletException {

        if(this.enable){
            request.setCharacterEncoding(encoding);
            response.setCharacterEncoding(encoding);
        }

        filterChain.doFilter(request, response);


    }

    public void init (FilterConfig config ) throws ServletException {
        this.config = config;
        loadConfigParams();


    }

    private void loadConfigParams() {
        this.encoding= this.config.getInitParameter("enconding");
        String flag = this.config.getInitParameter("enable");
        if(flag.equalsIgnoreCase("true")){
            this.enable = true;
        }else{
            this.enable = false;
        }


    }

}

web.xml

    encondingFilter
    com.morning.web.filter.CharacterEncodingFilter

        enconding
        utf-8


        enable
        true

encondingFilter
*.do

ply 2011-08-21 23:13 发表评论

JAVA经典算法40题

ply — Sun, 21 Aug 2011 15:11:00 GMT

摘要: 1: JAVA经典算法40题 2: 【程序1】题目：古典问题：有一对兔子，从出生后第3个月起每个月都生一对兔子，小兔子长到第四个月后每个月又生一对兔子，假如兔子都不死，问每个月的兔子总数为多少？ 3: 1.程序分析：兔子的规律为数列1,1,2,3,5,8,13,21.... ... 阅读全文

ply 2011-08-21 23:11 发表评论