rails3 the mysql configuration: Problem: Error: Please install the mysql2 adapter: `gem install activerecord-mysql2-adapter` The solution: Open the Web project Gemfile (in the root directory of the project site), will gem 'sqlite3' (If the command is
All the xhtml pages, Netbeans IDE encoding are both set to UTF8, but the back-end database this does not correspond to the encoding. First modified the mysql configuration file: my.ini (or my.conf), [mysql] default-character-set=UTF8 [mysqld] default
What is Clojure? Is a new language? Trouble is not Fana? This is the first language is not enough you with? Yes, each language is generally a little thing, but to so something special from time to learn the full reason. However, Clojure is really qui
1, set global wait_timeout = 10; vs set wait_timeout = 10; no need restart mysql 2, On thread startup, the session wait_timeout value is initialized from the global wait_timeout value or from the global interactive_timeout value, depending on the typ
mysql The installation startup problems To install the MySQL database linux os ,mysql-5.1.23-rc-linux-x86_64-icc-glibc23.tar.gz If you always read during the installation of the configuration file parameters, you can use the following command # Insta
MYSQL database coding problems exist, the main character will be reflected in the database, garbled, WEB page display unusual character. Summed up as only one reason: there will be places where there coding coding inconsistencies. WEB Development: MY
Using MySQL without a doubt the most headaches is the famous MySQL garbled, although always with Oracle, but as a good lightweight database, MySQL is undoubtedly the best choice. Long time no use in Linux, MySQL, and have again met in Ubuntu10.04 gar
To solve the problem MYSQL does not support Chinese MySQL's default encoding is Latin1, does not support Chinese, so how to modify MySQL's default encoding it, to UTF-8 the following example to illustrate the need to note that there is much room to m
First introduced to the situation I encounter: Action from the JSP page spread in the Chinese language is no problem, save the time it was the Chinese, save the results page is displayed in Chinese, but the database is garbled. Cause of the problem i
In our client and the remote connection with Mysql database server process, prone to the following questions: ERROR 2003 (HY000): Can't connect to MySQL server on '192.168.0.19' (111) Mysql database for this reason that the default configuration file
To reproduce the problem Let us first look at the following procedure: public class StaticInitSequence { //-------------------Static fields------------------- private static int staticIntVar = 10; private static int staticComputeIntVar = (int)(Math.r
ubuntu mysql After f Bahrain One is the copy from the support-files under. Copied to the mysql installation directory. And one in / etc / mysql / my.cnf here. When mysql start is to use the mysql installation directory under f file.
mysql table field memo varchar (700), I insert into table1 (memo) values ('attention to warm cold'); Insert in mysql browser when prompted to insert the total length of the data too long, Was found to be the table coding problem, modify the encoding
Recently I was asked whether a field in MySQL = NULL or && NULL is not matching the data in the framework of the layer or in the storage engine layer, and I said, if you look at the InnoDB table and the MyISAM table has this phenomenon , it is more
Sql file is created in the implementation of this table is always prompt an error, &KEY` user_id `(` user_id `) USING BTREE,& error encountered USING BTREE always eventually found to be low-mysql version, so relieved the original to re-install t
After a week of hard work has finally solved the problem, especially to extract the experience down note. This article will address the following question several garbled. Chinese into mysql table appears garbled, mysql from JSP page to read the data
Reproduced /tech/1000/61.html Quote I believe a friend of mine encountered this problem, especially not the first time installing mysql friends. Note: I said are in the mysql system windowsXP problem problem description is gener
mysql innodb in, or failure exists when the recovery recovery after a very long time problem, the next check, the original for the following reasons: When a fault occurs, restart the service, it will automatically resume operation before the database
&? xml version = '1 .0 'encoding =' UTF-8 '?& &! DOCTYPE hibernate-configuration PUBLIC &- / / Hibernate / Hibernate Configuration DTD 3.0 / / EN& & http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd && &
If the application to connect to local mysql, need to communicate with the database using the mysql.sock. adapter: mysql database: mydb username: root password: host: localhost socket: / var / lib / mysql / mysql.sock encoding: utf8 The Mysql itself
MySQL's character set support (Character Set Support) has two aspects: character set (Character set) and Sort (Collation). Character set support for refinement into four levels: Server (server), database (database), data table (table) and connection
Is transformed into the problem, find the height array, the demand max ((j-i + 1) * (min (height [i.. J]))), is equivalent to find one of the largest rectangle. Seeking F (a ^ b)% c because c is relatively small, the cycle can be derived section. Cod
Last group in a lot of people asking why their MySQL always garbled, one by one to answer very tired, where to paste it into the blog. Not much said to understand ..... see Figure Figure 1 Figure 2 Note into a red circle MySQL configuration has been
Freebsd mysql installed in the post-uninstall # Cd / usr / ports / database / mysql * / into the ports of the mysql installation directory # Make deinstall clean uninstall command Then when you install a new mysql error: mysql-server-5.4.2 cannot ins
Freebsd mysql installed in the post-uninstall # Cd / usr / ports / database / mysql * / into the ports of the mysql installation directory # Make deinstall clean uninstall command Then when you install the new mysql error: mysql-server-5.4.2 cannot i
Often encounter the &temporary table& and the &target list& merge of the situation, here merge_insert and merge_update a little stress. Is to first insert or the first update, this is a problem. Suppose &target list& of index
Modify the service executable file path Articles Category: JavaEye Problems that occur when installing mysql. In the mysqld-nt - install after installing the service. Net start mysql a &system error 2, the system can not find the file.& Solution
In cd / etc to create f as follows: # Example MySQL config file for medium systems. # # This is for a system with little memory (32M - 64M) where MySQL plays # An important part, or systems up to 128M where MySQL is used together with # Other
In order to smooth the development of a J2EE multi-language internationalization process, need to modify the database character set, my approach is as follows: Choose to install MySq UTF-8 character set Modify MySql installation directory configured
I am using a mysql-5.1.53-win32.msi the installation package, today reinstall mysql, always after the submission of the final configuration step, the installation fails, the process manager in the display program is not responding, mysql service star
MySql coding problems online order number: Here are a few under the MYSQL command: 1. View all character sets supported by the database 2. or \ View current status which includes of course the character
According to the online description. My.cnf file content changes 1. To find the cnf file location mysql find /-iname *. cnf 2. Casual copying one to the / etc / my.cnf - originally I did not copy here. But in / etc / mysql / my.cnf which i
According to the online description. Modify f file content 1 to find the cnf file location mysql find /-iname *. cnf 2. Just copy one to the / etc / my.cnf - I am not the original copy here. But in the / etc / mysql / my.cnf which
I am using mysql-5.1.53-win32.msi installation package today reinstall mysql, always after the submission of the final configuration step, the installation fails, the process manager in the display is unresponsive, mysql service starts Times 1067 err
Installing MySQL 5.0 First we install MySQL 5.0 like this: sudo apt-get install mysql-server mysql-client Create a password for the MySQL user root (replace yourrootsqlpassword with the password you want to use): sudo mysqladmin -u root password your
Like this. I created a sequence. first_ create sequence first_seq increment by 1 start with 100; Program, I use insert table values (first_seq.nextval ,.....); Now my question is, for example, I added 5 records. As Serial number attribute (the
The first step: simply delete MYSQL setup and installation program folder! ! (First stop mysql service and then deleted from the control panel) Step two: Check the C: \ WINDOWS directory and C: \ WINDOWS \ system32 whether the my.ini file, if it will
The original can be such that the mysql query select id, list, name from table where 'daodao' IN (list); (a) Note: 1. Table contains three fields id: int, list: varchar (255), name: varchar (255) In fact this is not enough, so that only when the name
To backup data, toss a mysql Toss nearly three days. Problems and solutions recorded as follows: Installation, Platform, redhat 5.5 x86-64bit, download the appropriate version of Quguan net mysql-server and mysql-client Using rpm package. running as
class MysqlPipeline(object): def process_item(self, item, spider): conn = MySQLdb.connect(host='localhost', user='root',passwd='') conn.set_character_set(&utf8&) conn.select_db('crawl_db'); cursor = conn.cursor() cursor.execute('set names utf8')
Wonder that strange, I use MySQL-Front Front tool to create a trigger using the wrong delimiter 1046 actually reported, but using cmd in the command, or can, indeed played a strange. . . Looking for a long time found that the trigger is created in a
Problem description: 1.mysql installation is complete, use service mysqld restart Always there stop mysqld service fails. 2. Using mysql-uroot-p log appears not find / var / lib / mysql / mysql.sock problem. 3. To use service mysqld status appear mys
Some time ago just completed a project, the database is MySQL5.0, persistence layer using Hibernate 3.2, not using the extra connection pool, then Hibernate will by default use it comes with a default connection pool, which is DriverManagerConnection
Problems encountered in the actual project is more, the Chinese say a mysql garbage problem, a student's, teacher help Tom, I have not plugged in the database over the Chinese, really did not find the problem, I tried a look at my program and found t
Windows7 + Apache + MySql + PHP problem of slow response to bother me for many days. Google has a lot of information, made a number of experiments have not tried many ways to solve well, only slightly improved. In the circle around the N, finally fou
First, install the 1, download the installation files to install MySQL MySQL needs the following two files: MySQL-server-4.0.16-0.i386.rpm MySQL-client-4.0.16-0.i386.rpm Download address: /downloads/mysql-4.0.html, open this page,
Have a question, why mysql is not installed on the same file directory? So many directories, what is the purpose then? May be a simple answer: In order to facilitate, consistent with storage standards, such as / Usr / bin Client programs and scripts
MySQL master-slave synchronization mechanism is very convenient to solve the high concurrent read the application requirements, to the Web aspects of development has brought great convenience. However, this approach has a relatively large defects is
Original Address: http://blog.chinaunix.net/u2/82530/showart_1956918.html Download page: http://dev.mysql .com/downloads/mysql/5.0.html # downloads To the bottom of the page to find the Source downloads, this is the source version, download the first
Log appears 1130 is not allowed to connect to this MySql server problem, the solution is as follows: Root user name you want to use the root password from any host to connect to the mysql server, then. GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' IDENTI
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processed in 0.059 (s). 9 q(s)0、 需要标识符a) 不在函数内1、 非法表达式开始b) 可能:丢失括号 .2. no data founda) 可能:setInt(1,100)中,没有100这个值3. 找不到符号a) 可能:没导入包4. 指定了无效URLa) 可能:数据库名或IP错误,即连接出错5. 类路径没有找到a) 可能: ClassNotFoundException: oracle.jdbc.driver.OracleDriverb) 原因: 一般是指包名写错,或者没有import包,或者没有在类路径中找到jar文件c) 解决: 没有加载Oracle驱动jar,在.bash_profile中把ojdbc14.jar加进来6. 空指针异常a) 可能: 数据源错误 比如数据库名或IP错误7. 不能执行查询a) 可能: 数据库中表的问题,比如列名不存在8. invalid identitya) 可能: 列名出错9. 若在数据库中创建了 两个sequence ,运行时出现异常可能是先后执行了多次select语句,导致与原有的序列号产生冲突10. 表名或列名不存在a) 可能:表不存在或者没有插入数据到表中11. 不支持的类,类的版本错误a) 可能:没有导入jdk5.0,或者编译器仍为1.412. MappingNotFoundExceptiona) Maybe: In the Eclipse Not refersh , or not exist in the dirctory13. HibernateException: /hibernate.cfg.xml not founda) Maybe1: hibernate.cfg.xml not in the root directoryb) Maybe2: Could not parse configuration .c) resolve: database not connect or use another database14. ConstraintViolationExceptiona) Maybe: used a not true database15. 驱动没有找到 或者 JDBC Driver not found可能：连接数据库的驱动jar包不存在或者版本不一致，比如将旧的版本换成新的会造成该类错误16. 空指针异常 ， java.lang.NullPointerExceptiona) 可能1：数据库连接出错，比如在hibernate.cfg.xml中的数据错误会导致异常。17. 数据插入异常 ，GenericJDBCException: could not inserta) 可能1：没有建立表或者表中没有任何数据b) 可能2：插入数据后没有执行提交语句：commit18. LazyInitializationException 或者延迟加载异常a) 可能1：没有在查询语句中加fetch19. IdentifierGenerationExceptiona) 可能1：高位表没有初始化（比如hi_value中没有记录)20. could not initialize a collection: [hibernate.entity.Role.modules#32768] Syntax error: Encountered "-" at line 1, column 132.a) 错误原因：&set name="modules" table="module-role" lazy="false"&红色字部分中“-”为非法字符，替换为module_role21. could not insert collection rows: [hibernate.entity.Module.roles#1]在Module.hbm.xml文件的如下配置中加入inverse=”true”&set name="roles" table="module_role" inverse="true"&22．在部署Struts时，出现如下错误信息：HTTP Status 404 - Servlet action is not availabletype Status reportmessage Servlet action is not availabledescription The requested resource (Servlet action is not available) is not available.问题原因：1.、web.xml文件中未配置ActionServlet。2、struts-config.xml文件未配置你要访问的Action。3、你的jsp文件form标记中action属性的路径名称错误。4、非以上三种情况。针对以上4种情况相应的解决方案如下：1、在web.xml文件中加上ActionServlet的配置信息?????? /WEB-INF/struts-config.xml??2、在struts-config.xml文件检查你要访问的Action配置文件。3、检查jsp文件form标记中action属性的路径名称是否与struts-config.xml文件中action标记的path属性的路径名称一致。4、非以上情况的解决办法就是检查web容器的log日志，如果时tomcat则检查下logs目录下的localhost_log文件，看里边是否记录有错误信息，然后根据错误信息提示将其纠正。23．java.lang.NoClassDefFoundError: org/apache/commons/beanutils/Converter缺少spring-framework-2.0.3\lib\jakarta-commons\commons-beanutils.jar24.ava 代码Caused by: java.lang.NoClassDefFoundError: org/objectweb/asm/Type&&缺少spring-framework-2.0.3\lib\asm\asm-2.2.2.jar包,版本不同,该包的名字有相应的区别java 代码Caused by: java.lang.NoClassDefFoundError: org/dom4j/DocumentException&&缺少spring-framework-2.0.3\lib\dom4j\dom4j-1.6.1.jar包,版本不同,该包的名字有相应的区别把这个包进去就可以了：\Spring206\lib\dom4j、dom4j-1.6.1.jarjava 代码Caused by: java.lang.NoClassDefFoundError: org/apache/commons/collections/SequencedHashMap&&缺少spring-framework-2.0.3\lib\jakarta-commons\commons-collections.jar包,版本不同,该包的名字有相应的区别java 代码Caused by: java.lang.NoClassDefFoundError: net/sf/cglib/proxy/CallbackFilter&&缺少spring-framework-2.0.3\lib\cglib\cglib-nodep-2.1_3.jar包,版本不同,该包的名字有相应的区别java 代码Caused by: java.lang.NoClassDefFoundError: org/objectweb/asm/CodeVisitor&&缺少hibernate-3.2\lib\asm.jar包,版本不同,该包的名字有相应的区别java 代码org.hibernate.exception.SQLGrammarException: could not load an entity: [www.proudsoul.xml.User#1]JAVA工程与WEB工程包的区别:一个是asm.jar,一个是jta.jarjava 代码Caused by: java.lang.NoClassDefFoundError: javax/transaction/TransactionManager&&缺少spring-framework-2.0.3\lib\j2ee\jta.jar包,版本不同,该包的名字有相应的区别此种错误请检查相应的***.hbm.xml配置文件的配置25,Exception in thread "main" org.springframework.dao.InvalidDataAccessResourceUsageException: could not get nested exception is org.hibernate.exception.SQLGrammarException: could not get next sequence valueCaused by: org.hibernate.exception.SQLGrammarException: could not get next sequence value原因：没有加Sequence或者数据库的方言写错了26,我的配置文件&&&&&id name="id" column="id"&&&&&&&&&&&&&&generator class="native" /&&&&&&&&&&/id&然后我运行保存一条数据进去The database returned no natively generated identity value就会报这个错误因为你native是根据看底层数据库的能力选择identity, sequence 或者hilo中的一个而我建表的时候id没有指定alter table `student` change `id` `id` int auto_increment我们把我们的表的结构小小的改动一下就没问题了27,UpdateManager无法启动 15:21如果在应用程序安装过程中，暴力中断安装程序，会出现如下状况：1.apt-get remove 和dpkg --remove 无法删除软件 2.UpdateManager无法启动3.新立得软件包管理程序无法启动以上可能是deb损坏之类造成的sudo dpkg -r sqldveloper正在读取软件包列表... 完成正在分析软件包的依赖关系树... 完成E: 软件包 sqldeveloper 需要重新安装，但是我无法找到相应的安装文件。解决方法：1.从 /var/lib/dpkg/status 中把对应的段删掉重要：修改之前请先备份在status中找到你对应的包删除就OK了...28,Exception in thread "main" java.lang.NoClassDefFoundError: antlr/ANTLRException少了antlr-2.7.5H3.jar包,从D:\eclipse\eclipse\plugins\com.genuitec.org.hibernate.eclipse_4.1.1\myeclipse-data\3.0\lib29,Caused by:java.lang.NoClassDefFoundError: javax/transaction/Synchronization缺少Spring206\lib\j2ee\jta.jar30,Caused by:java.lang.IllegalArgumentException: Cannot convert value of type [$Proxy3] to required type [business.impl.PriceBiz] for property 'priceBiz': no matching editors or conversion strategy found在java类中设置priceBiz时应该设置的是接口PriceBizIf，而非实现类31, 数组越界可能1: 在命令行后面需要加入参数.可能2:加入的参数错误32, car is not mapped可能1: 在cfg.xml中没有增加映射的hbm.xml文件在&mapping.../&中&&33, 属性没有找到可能1: hbm.xml文件中的 &property name =""& 有问题, 也许是name的值与对应类中的成员名不一致34,SQLException: 无当前连接&&&&&&&&&&可能1:在比如创建帐户时没有对相应的方法添加到&list&中去,比如这个没有加入:&value&newAccount&/value&
Java代码&&
&bean&id="transactionAdvisor"&class="org.springframework.aop.support.NameMatchMethodPointcutAdvisor"& &&
&&&&property&name="advice"& &&
&&&&&ref&bean="advice"/& &&
&&&&/property& &&
&&&&property&name="mappedNames"& &&
&&&&&list& &&
&&&&&&value&transfer&/value& &&
&&&&&/list& &&
35,SQLException: Syntax error: Encountered "table" at line 1, column 8.可能1;执行SQL时出现冲突,可能是SQL语句中使用了关键字作为变量来用,比如&&&update order set balance=1000000;&&&其中order被用作表名来使用,这是错误的,因为order是个关键字,用在order by中36, Servlet /Spring-WebMvc threw load() exceptionorg.xml.sax.SAXParseException: Document root element "beans", must match DOCTYPE root "null".jar包的冲突,spring-1.2.6.jar和spring.jar出现在一个war的目录中:JBoss/server/all/deploy/Spring-WebMvc.war/WEB-INF/lib&&&37, java.sql.SQLException: 当事务仍处于活动状态时，无法关闭连接。38 ,validateJarFile(/home/soft01/Tomcat/webapps/sms-token-struts/WEB-INF/lib/servlet-api.jar)Servlet /sms-struts-tiles threw load() exceptionjava.lang.ClassNotFoundException: org.apache.struts.action.ActionServlet原因:在WEB-INF/lib/ 目录下有servlet-api.jar与/Tomcat/common/lib目录下的servlet-api.jar冲突了,把WEB-INF/lib/下的servlet-api.jar删除就可以了39,java.lang.ClassNotFoundException: org.springframework.web.struts.ContextLoaderPlugInMarking servlet action as unavailable10:30:47,088 ERROR [/NetCT_OSS]:3953 - Servlet /NetCT_OSS threw load() exceptionjavax.servlet.UnavailableException40,org.xml.sax.SAXParseException: Document root element "beans", must match DOCTYPE root "null".缺少MyEclipse/eclipse/plugins/com.genuitec.eclipse.springframework_5.5.0/data/2.0/dist/modules/spring-struts.jar41,Caused by: java.sql.BatchUpdateException: ORA-02291: integrity constraint (SD0702.FK82D343CF49A4B831) violated - parent key not foundCaused by: org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update有可能是ID生成策略的问题,我将它XML映射文件改成&generator class="increment" /&就好了42, 16:21:43,290 ERROR [org.apache.catalina.core.ContainerBase.[Catalina].[localhost].[/OSS].[action]] - Servlet.service() for servlet action threw exceptionorg.hibernate.NonUniqueObjectException: a different object with the same identifier value was already associated with the session: [entity.Module#2]java.util.ConcurrentModificationException原因:已经有对象拥有了所选择的module,用clear(),而不是remove();43,ERROR [org.apache.catalina.session.ManagerBase] - IOException while loading persisted sessions: java.io.InvalidClassException: entity.M local class incompatible: stream classdesc serialVersionUID = -5445758, local class serialVersionUID = -484429java.io.InvalidClassException: entity.M local class incompatible: stream classdesc serialVersionUID = -5445758, local class serialVersionUID = -484429在Module中加上一个关键字:transient44,Caused by: java.sql.BatchUpdateException: ORA-02292: integrity constraint (SD0702.SYS_C) violated - child record found原因:有其他的表引用了该表的外建,所以报这个异常,如果没有引用就不会出现45,出现数组越界的时候,看看是不是循环时没有加=,比如:for(int i = 1; i&arr.i++)可以改成for(int i = 1; i&=arr.i++)46.如果使用Ant和Junit是被报找不到test,检查一下是否误用了private出错信息：&&&&&failure message="No tests found in test.AllTest" type="junit.framework.AssertionFailedError"&junit.framework.AssertionFailedError: No tests found in test.AllTest该错误有个很特别的特点，当你不通过ant来运行测试，而是通过AllTest类来运行的话，可以正常运行。小心哦47.如果遇到报：表名无效，且jvm报严重错误，看看是不是用了数据库的保留关键字来做表名了，如User。48.使用ant时必须小心ant的classpath它用的不是IDE的classpath，小心!49.小心下边的异常，exception setting property value with CGLIB (set hibernate.cglib.use_reflection_optimizer=false for more info) setter of xp.bean.Users.?" type="net.sf.hibernate.PropertyAccessException"&java.lang.ClassCastException at xp.bean.UsersMetaClass1.setPropertyValues(&generated&) at net.sf.hibernate.persister.AbstractEntityPersister.setPropertyValues上次出现该错错误的原因是:源文件里我的class类型为一个类Contact contact而跑到mapping里却成了Set,呵呵厉害。50.突然间冒出大量的NullPointException重新build一下。51.="Flush during cascade is dangerous - this might occur if an object was deleted and then re-saved by cascade"52.Tapestry的出错信息：Class com.bookshop.Hello does not implement the IPage interface.location: context:/WEB-INF/Home.page, line 6原因：与显示有关的哪个java类没有从IPage家族继承。53.使用ant时给出的路径好象不允许出现空格。54.由于使用ant时用junit做测试的话，classpath中出现j2ee.jar的话，问题多多。例如xml格式的log文件生成不了，莫名其妙的NullPointException等。所以我设置了两个包个包含j2ee.jar，为编译用；一个没有,为junit用55.进行单元测试时，在查询返回后应马上assertNotNull()，这样可以更快速的定位NullPointException56.要使用ResourceBundle的话，要千万小心。必须用日志记录下它的状态。还有该属性文件应该放在classes下面。57.当要显示任何页面时，都被提示无效，那么应该检查一下lib目录了，还有一些很奇怪的异常，例如你明明可以找到一个类但是服务器却提示ClassNotDefException，那么估计是缺少了该类所必须的包了。或者多了不兼容的包，如, xdoclet系列包不被struts的lib目录所兼容58.编写clone时从Java编程思想(2nd)上学到的(732)：.引数传递过程中会自动产生别名(alias)。.没有局域对象(local objects)，只有局域性的(local)references。.reference受范围(scope)的限制，对象则否。.对象的寿命从来不是Java的讨论议题(因为有垃圾回收机制)59.try catch finally的域居然是分离的。60.jsp乱码的其中一个原因：charset="gb2312" 等号"="的两边不允许有空格。61.我的基于Displaytag的简单报表解决方案。http://displaytag.sourceforge.net/下载displaytag.jar和displaytag.tlddisplaytag.jar放在lib目录，而displaytag.tld放在WEB-INF目录，在web.xml中为displaytag.tld声明一下。&taglib&&&&&&taglib-uri&http://displaytag.org&/taglib-uri&&&&&&taglib-location&/WEB-INF/displaytag.tld&/taglib-location&&/taglib&在jsp里使用前，加上&%@ taglib uri="http://displaytag.org" prefix="display" %&&&&&&&&注意该软件有个bug，他要用的一个包common-lang.jar版本必须在2.0以上。如果碰到下面异常，则应坚持一下是否该包的版本问题。java.lang.NoSuchMethodError: mons.lang.StringUtils.capitalize(Ljava/lang/S)Ljava/lang/S然后就可放心使用了&display:column property = "xxx"/&其中xxx为对象中的带有getter的变量&。定义表格的样子，用css定义。如TABLE.its THEAD TR {BACKGROUND-COLOR: #69c}TABLE.its TR.even {BACKGROUND-COLOR: #def}在使用分页时，可能会出现这种情况，点击其他页时，弹出下载窗口，让你下载当前jsp页面，这是因为你在当前页面读取了数据的缘故。解决办法为在action里读取数据而不是在jsp里。可以参考http://www.displaytag.org/example-paging.jsp?d-26189-p=262.使用displaytag时，在一列中放入多个元素必须在display:table中定义一个id&display:table name = "allBooks" class = "its" pagesize = "5" id = "item"&&display:column title = "操作"&&&&&&a href = "/Bookshop/admin/bookManagement.do?action=view&id=&%=((Book)item).getId()%&" target = "_blank" &查看&/a&&&&&&a href = "/Bookshop/admin/bookManagement.do?action=edit&id=&%=((Book)item).getId()%&"&编辑&/a&&&&&&a href = "/Bookshop/admin/bookManagement.do?action=delete&id=&%=((Book)item).getId()%&"&删除&/a&&/display:column&要在displaytag中使用链接，必须具备paramId，否则不显示为链接&display:column property = "product.name" href = "viewDetailV2.0.jsp" title = "书名" paramId="item" paramProperty="product.id"/&可以这样使用display&display:column property = "product.id" title = "ID"/&其中product为对象63.&bean:write name = "xxxx" property = "xxx"/& 可以直接取到session.getAttribute()取到的东西。64.实验struts-upload例子时要注意的地方：&&&1.If you would rather write this file to another file, please check here:这一行要打钩&&&2.If you checked the box to write to a file, please specify the file path here:在这里要重命名如：c:\b.jpg上传成功的话，会出现提示 The file has been written to "c:\b.jpg"65.Hibernate的like可以这么用：&&&&&&Query query = session.createQuery("from src.persistent.Book as book where upper(book.name) like :name ");&&&&&&query.setString("name", "%");&&&&&&result = query.list();66.Hibernate出现 duplicate import : className异常也可能是因为忘了为持久类在configuration中addClass了&&&&&67.&logic:iterate id = "author" name = "authors"&name所引用的是session里的attribute。68.如果发现要出现询问下载的情况，有可能是因为要跳转的页面出现了问题。试试在要跳转到的页删掉&%@ page contentType="text/ charset=gb2312"%&69.如果JSP页面跳转时出现下边的错误信息：The request sent by the client was syntactically incorrect (Invalid path /web/shoppingCart was requested).原因是struts-config的action = "x" 写成了 action = "x.do"70.在struts中，strut-config.xml中，forward时使用redirect = "true"可以将.do重定向为.jsp71.以后在判断相等性之前先用logger把两个值显示出来。72.从session里getAttribute后，修改并不需要重新setAttribute一次。73.在hibernate中使用subclass是一棵继承树共用一个表，仅生成个mapping。每个类中必须有discrimator-value。在最上层的类中必须声明：@hibernate.discriminator column = "class"。不可以将子类添加到configuration里去。(即不可addClass(子类))使用Xdoclet的建立subclass的例子(该类是父类)而使用joined-subclass则是一类一表,也不许将子类添加进configuration里去。如果发现生成的mapping文件中joined-subclass的key column为空，那么可能是@hibernate.joined-subclass-key这句没有写对。用joined-subclass生成的表，仔细看。Member extends Customercreate table Customer (&&&id VARCHAR2(255) not null,&&&name VARCHAR2(255),&&&description VARCHAR2(255),&&&primary key (id))create table Member (&&&customer_id VARCHAR2(255) not null,&&&password VARCHAR2(255),&&&primary key (customer_id))74.在junit中尽量使用assertEquals代替assertT75.Hibernate如果Child extends Parent那么from Parent as parent 也将会将Child选出来，而from Child as child 则不会选出Parent76.Hibernate使用hibernate的one-to-one时，应该两方向都set,否则会报save NullPointExceptionparent.setChild(child);child.setParent(parent);77.Hibernate遇到下边的异常，估计是与因为外键出现了问题：java.lang.NullPointerExceptionat net.sf.hibernate.persister.AbstractEntityPersister.getPropertyValue(AbstractEntityPersister.java:675)at net.sf.hibernate.id.ForeignGenerator.generate(ForeignGenerator.java:33)如:* @hibernate.id generator-class = "foreign"* @hibernate.generator-param name = "property" value = "customer"* @hibernate.one-to-one name = "custmoer" class = "src.persistent.Customer"value的值和one-to-one 中name的值不符，则会出现上边的异常。如果不显示指定name则默认取成员变量名如Customer a则name = "a" 需要小心的是不是类名。所以，以后最好显示指定名字为好。78.出现异常：Exceptionobject references an unsaved transient instance - save the transient instance before flushing: src.persistent.Product原因没有为某对象进行set设置， 如上边的这个就是某对象没有调用setProduct79."xxx action = "/a" 不用.do和根目录名&a href = "b.do" 需要.do和根目录名80.Caused by: java.sql.SQLException: ORA-02291: 违反完整约束条件 (BOOKSHOP.FK4AAEE47687CCA6B) - 未找到父项关键字如果你觉得该做的e是出现这个问题，那么检查一下，是否将类的继承关系在hibernate的mapping中反映了出来。joined-subclass或subclass例如a extends b如果持久类c 需要Set的是持久类a，那么你把b传入，而b又没有在mapping中将父子关系反映出来的话，就会出现该异常81.使用DynaActionForm需要注意的问题在struts-config声明&form-bean name="memberloginForm" dynamic ="true" type="org.apache.struts.action.DynaActionForm"&&form-property name = "name" type = "java.lang.String"/&&form-property name = "password" type = "java.lang.String"/&&/form-bean&在Action里将form强制转化成DynaActionForm，然后get("属性名")就可以了82.struts的validate最简单实现1.首先准备好错误提示信息。xxx.properties 里errors.required={0} is required.(默认已有)2.Form必须从ValidatorForm继承3.不可以重载ValidatorForm的validate函数4.在validate.xml中为你想验证的表单进行验证设计。例如&form name="logonForm"&&&&&&field property="userName" depends="required"&&arg0 key="prompt.userName"/&(该参数将在显示错误信息是从xxx.properties读取prompt.userName,填入{}方括号里，取代0。如果是arg1将将填入{1}位置，以此类推。&&&&&/field&&/form&不需要在action里做任何处理。只管forward就行了。作为forward的目标页，不需要任何有关用于处理出错信息的处理。83.服务器报The requested resource (/xxxx/xxx.htm) is not available.的很奇怪的一个的可能原因在web.xml中定义的tld，没有找到或者是lib目录下的包太多出现了问题。如&taglib&&&&&&taglib-uri&/spring&/taglib-uri&&&&&&taglib-location&/WEB-INF/spring.tld&/taglib-location&&/taglib&如WEB-INF目录下不存在spring.tld的话，就会报上边的错误84.spring的xxx-servlet.xml的使用SimpleFormController系列的类问题：&bean id = "priceIncreaseForm" class="PriceIncreaseFormController"&&&&&&property name="sessionForm"&&value&true&/value&&/property&&&&&&property name="beanName"&&value&priceIncrease&/value&&/property&&&&&&property name="commandClass"&&value&PriceIncrease&/value&&/property&&&&&&property name="formView"&&value&priceIncrease&/value&&/property&&&&&&property name="successView"&&value&hello&/value&&/property&&&&&&property name="productManager"&&&&&&&&ref bean="prodMan"/&&&&&&/property&&/bean&这里要注意几个问题：(1)上边的PriceIncrease是了类名，必须在classes里存在该类，否则报：PropertyVetoExceptionsException: 1 errors:-- ErrorCodedPropertyVetoException: message=[Failed to convert property value of type [java.lang.String] to required type [java.lang.Class] for property named 'commandClass'; nested exception is:java.lang.IllegalArgumentException: Invalid class name [PriceIncrease]: PriceIncrease]; errorCode=[typeMismatch]java.lang.IllegalArgumentException: Invalid class name [PriceIncrease]: PriceIncrease(2)&property name="formView"&&value&priceIncrease&/value&&/property&这一行必不可少，priceIncrease是页面的名字，他将会是prefix + priceIncrease + suffix如果缺少该行，则报：javax.servlet.ServletException: Error in ModelAndView object or View resolution encountered by servlet with name 'pocketSpring': View to render cannot be null with ModelAndView [ModelAndView: materialized View is [null]; Model=[{priceIncrease=PriceIncrease@148e798, org.springframework.validation.BindException.priceIncrease=org.springframework.validation.BindException: BindException: 0 errors}]]使用Errors的rejectValue相关问题：rejectValue(java.lang.String field, java.lang.String errorCode, java.lang.Object[] errorArgs, java.lang.String defaultMessage)Reject the given field of the current object, using the given error description.当前对象指的是xxx-servlet.xml中与validator类有联系的哪个对象。&&&&&&&&&第一个是：当前对象的属性名，必须存在第二个是：将要从属性文件中读取的消息第三个是：传递给所读取的消息的参数，如：error.too-low=You have to specify a percentage higher than {0}!第四个是：当从属性文件中读取消息不成功时，所reject的值以后从request中读取parameter可以借用spring的RequestUtils包里的getStringParameterpublic static java.lang.String getStringParameter(javax.servlet.http.HttpServletRequest request,&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&java.lang.String name,&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&java.lang.String defaultVal)Get a string parameter, with a fallback value. Never throws an exception. Can pass a distinguished value to default to enable checks of whether it was supplied.不会抛异常Hibernate的问题：2.1rc的问题INFO: cache provider: net.sf.ehcache.hibernate.Providernet.sf.hibernate.HibernateException: could not instantiate CacheProvider:解决办法，2.1rc比以前的版本多需要一个包ehcache.jar85.static的问题static函数只可以访问static成员变量。而static变量可以被任何成员函数访问。86.java.lang.NoClassDefFoundError: javax/transaction/Synchronization];需要添加JTA.jar以后再遇到别的错误继续添加！
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