在练习ssh项目时遇到的问题及解决方法

1.通配符的匹配很全面, 但无法找到元素 'context:property-placeholder' 的声明

2.报下错时，需要导入struts2-spring-plugin-2.2.1.jar包

严重: Exception starting filter struts2
Unable to load configuration. - action - file:/F:/Tomcat7.0/webapps/Map/WEB-INF/classes/struts.xml:7:55
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:428)
at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:69)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:51)
at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:279)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:260)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:105)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4939)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5633)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
at org.apache.catalina.startup.HostConfig.reload(HostConfig.java:1548)
at org.apache.catalina.startup.HostConfig.checkResources(HostConfig.java:1512)
at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1748)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:333)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1370)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1542)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1552)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1520)
at java.lang.Thread.run(Thread.java:745)
Caused by: Unable to load configuration. - action - file:/F:/Tomcat7.0/webapps/Map/WEB-INF/classes/struts.xml:7:55
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:69)
at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:371)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:415)
... 19 more
Caused by: Action class [mapAction] not found - action - file:/F:/Tomcat7.0/webapps/Map/WEB-INF/classes/struts.xml:7:55
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.verifyAction(XmlConfigurationProvider.java:420)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addAction(XmlConfigurationProvider.java:365)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:479)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:275)
at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:111)
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:204)
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:66)
... 21 more

3.报下错时，需要在web.xml中配置ContextLoaderListener,使得在启动web容器时，自动加载applicationContext.xml文件。

严重: Exception starting filter struts2
Class: com.opensymphony.xwork2.spring.SpringObjectFactory
File: SpringObjectFactory.java
Method: getClassInstance
Line: 220 - com/opensymphony/xwork2/spring/SpringObjectFactory.java:220:-1
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:428)
at org.apache.struts2.dispatcher.ng.InitOperations.initDispatcher(InitOperations.java:69)
at org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter.init(StrutsPrepareAndExecuteFilter.java:51)
at org.apache.catalina.core.ApplicationFilterConfig.initFilter(ApplicationFilterConfig.java:279)
at org.apache.catalina.core.ApplicationFilterConfig.getFilter(ApplicationFilterConfig.java:260)
at org.apache.catalina.core.ApplicationFilterConfig.<init>(ApplicationFilterConfig.java:105)
at org.apache.catalina.core.StandardContext.filterStart(StandardContext.java:4939)
at org.apache.catalina.core.StandardContext.startInternal(StandardContext.java:5633)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:147)
at org.apache.catalina.startup.HostConfig.reload(HostConfig.java:1548)
at org.apache.catalina.startup.HostConfig.checkResources(HostConfig.java:1512)
at org.apache.catalina.startup.HostConfig.check(HostConfig.java:1748)
at org.apache.catalina.startup.HostConfig.lifecycleEvent(HostConfig.java:333)
at org.apache.catalina.util.LifecycleSupport.fireLifecycleEvent(LifecycleSupport.java:117)
at org.apache.catalina.util.LifecycleBase.fireLifecycleEvent(LifecycleBase.java:90)
at org.apache.catalina.core.ContainerBase.backgroundProcess(ContainerBase.java:1370)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1542)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.processChildren(ContainerBase.java:1552)
at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1520)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
at com.opensymphony.xwork2.spring.SpringObjectFactory.getClassInstance(SpringObjectFactory.java:220)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.verifyResultType(XmlConfigurationProvider.java:530)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addResultTypes(XmlConfigurationProvider.java:501)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.addPackage(XmlConfigurationProvider.java:457)
at com.opensymphony.xwork2.config.providers.XmlConfigurationProvider.loadPackages(XmlConfigurationProvider.java:275)
at org.apache.struts2.config.StrutsXmlConfigurationProvider.loadPackages(StrutsXmlConfigurationProvider.java:111)
at com.opensymphony.xwork2.config.impl.DefaultConfiguration.reloadContainer(DefaultConfiguration.java:204)
at com.opensymphony.xwork2.config.ConfigurationManager.getConfiguration(ConfigurationManager.java:66)
at org.apache.struts2.dispatcher.Dispatcher.init_PreloadConfiguration(Dispatcher.java:371)
at org.apache.struts2.dispatcher.Dispatcher.init(Dispatcher.java:415)
... 19 more

web.xml中添加：

<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:applicationContext.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

4.postgresql数据库表(表名最好都小写)的主键自增设置参考Postgresql 创建主键并设置自动递增的三种方法，由于事先已建好表，所以用了第三种方法：

对maps表生成自动增长序列，在sql编辑器下执行下列语句

CREATE SEQUENCE maps_id_seq
START WITH 1
INCREMENT BY 1
NO MINVALUE
NO MAXVALUE
CACHE 1;

接着执行

alter table maps alter column id set default nextval('maps_id_seq');

就可以在插入数据时实现主键自增操作了。

接着在与Hibernate一起使用时，配置Maps.hbm.xml时也需要设置主键的自增模式，参考NHibernate 连接PostgreSql的配置，以及generator配置id自增长，可写成如下：

<id name="id" type="java.lang.Integer">
<column name="id" />
<generator class="sequence">
<param name="sequence">maps_id_seq</param>
</generator>
</id>

其中maps_id_seq就是先前生成的自增序列，如下所示：

可自行设置递增量和当前值。