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Java面试题集(六)

2017-05-01 14:44 489 查看
以下为框架补充部分:

Struts 2中,Action通过什么方式获得用户从页面输入的数据,又是通过什么方式把其自身的数据传给视图的?
Action从页面获取数据有三种方式:
①通过Action属性接受参数
②通过域模型获取参数
③通过模型驱动获取参数 (ModelDriven<T>)
Action将数据存入值栈(Value Stack)中,视图可以通过表达式语言(EL)从值栈中获取数据。
阐述Struts 2中的Action如何编写?Action是否采用了单例?
Struts2的Action有三种写法:
①POJO
②实现Action接口重写execute()方法
③继承ActionSupport类
Action没有像Servlet一样使用单实例多线程的工作方式,很明显,每个Action要接收不同用户的请求参数,这就意味着Action是有状态的,因此在设计上使用了每个请求对应一个Action的处理方式。

hibernate如何实现分页查询?
通过Hibernate实现分页查询,开发人员只需要提供HQL语句、查询起始行数(setFirstresult()方法)和最大查询行数(setMaxResult()方法),并调用Query接口的list()方法,Hibernate会自动生成分页查询的SQL语句。

web.xml 的作用?
用于配置Web应用的相关信息,如:监听器(listener)、过滤器(filter)、Servlet、相关参数、会话超时时间、安全验证方式、错误页面等。
例如:
①配置spring上下文加载监听器加载Spring配置文件:

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<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>    



<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>

②配置Spring的OpenSessionInView过滤器来解决延迟加载和Hibernate会话关闭的矛盾:

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<filter>      
  <filter-name>openSessionInView</filter-name>      
  <filter-class>      
     org.springframework.orm.hibernate3.support.OpenSessionInViewFilter      
  </filter-class>      
</filter>      
<filter-mapping>      
  <filter-name>openSessionInView</filter-name>      
  <url-pattern>/*</url-pattern>      
</filter-mapping>  



<filter>
<filter-name>openSessionInView</filter-name>
<filter-class>
org.springframework.orm.hibernate3.support.OpenSessionInViewFilter
</filter-class>
</filter>
<filter-mapping>
<filter-name>openSessionInView</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>


③配置会话超时时间为10分钟:

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<session-config>      
     <session-timeout>10</session-timeout>      
   </session-config>  



<session-config>
<session-timeout>10</session-timeout>
</session-config>


④配置404和Exception的错误页面:

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<error-page>      
  <error-code>404</error-code>      
  <location>/error.jsp</location>      
</error-page>        
<error-page>      
  <exception-type>java.lang.Exception</exception-type>      
  <location>/error.jsp</location>      
</error-page>   



<error-page>
<error-code>404</error-code>
<location>/error.jsp</location>
</error-page>
<error-page>
<exception-type>java.lang.Exception</exception-type>
<location>/error.jsp</location>
</error-page>


⑤配置安全认证方式:

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  <security-constraint>      
      <web-resource-collection>      
       <web-resource-name>ProtectedArea</web-resource-name>      
        <url-pattern>/admin/*</url-pattern>      
       <http-method>GET</http-method>      
        <http-method>POST</http-method>      
      </web-resource-collection>      
      <auth-constraint>      
        <role-name>admin</role-name>      
      </auth-constraint>      
    </security-constraint>             
    <login-config>      
      <auth-method>BASIC</auth-method>      
    </login-config>      
    <security-role>      
      <role-name>admin</role-name>      
</security-role>  



<security-constraint>
<web-resource-collection>
<web-resource-name>ProtectedArea</web-resource-name>
<url-pattern>/admin/*</url-pattern>
<http-method>GET</http-method>
<http-method>POST</http-method>
</web-resource-collection>
<auth-constraint>
<role-name>admin</role-name>
</auth-constraint>
</security-constraint>
<login-config>
<auth-method>BASIC</auth-method>
</login-config>
<security-role>
<role-name>admin</role-name>
</security-role>


你的项目中使用过哪些JSTL标签?
项目中主要使用了JSTL的核心标签库,包括<c:if>、<c:choose>、<c:
when>、<c: otherwise>、<c:forEach>等,主要用于构造循环和分支结构以控制显示逻辑。
说明:虽然JSTL标签库提供了core、sql、fmt(日期或数字格式化)、xml等标签库,但是实际开发中建议只使用核心标签库(core),而且最好只使用分支和循环标签并辅以表达式语言(EL),这样才能真正做到数据显示和业务逻辑的分离,这才是最佳实践。

如何在Web项目中配置Spring的IoC容器?

如果需要在Web项目中使用Spring的IoC容器,可以在Web项目配置文件web.xml中做出如下配置:

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<context-param>      
    <param-name>contextConfigLocation</param-name>      
    <param-value>/WEB-INF/daoContext.xml /WEB-INF/applicationContext.xml</param-value>      
</context-param>      
<listener>      
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>      
</listener>   



<context-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/daoContext.xml /WEB-INF/applicationContext.xml</param-value>
</context-param>
<listener>
<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>


如何在Web项目中配置Spring MVC?

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<servlet>  
<description>spring mvc servlet</description>  
<servlet-name>springMvc</servlet-name>  
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  
<init-param>  
<description>spring mvc 配置文件</description>  
<param-name>contextConfigLocation</param-name>  
<param-value>classpath:spring-mvc.xml</param-value>  
</init-param>  
<load-on-startup>1</load-on-startup>  
</servlet>  
<servlet-mapping>  
<servlet-name>springMvc</servlet-name>  
<url-pattern>*.do</url-pattern>  
</servlet-mapping>  



<servlet>
<description>spring mvc servlet</description>
<servlet-name>springMvc</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<description>spring mvc 配置文件</description>
<param-name>contextConfigLocation</param-name>
<param-value>classpath:spring-mvc.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>springMvc</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>


如何在Spring IoC容器中配置数据源?

1.DBCP配置:

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<bean id="dataSource"      
        class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">      
    <property name="driverClassName" value="${jdbc.driverClassName}"/>      
    <property name="url" value="${jdbc.url}"/>      
    <property name="username" value="${jdbc.username}"/>      
    <property name="password" value="${jdbc.password}"/>      
</bean>          
<context:property-placeholder location="jdbc.properties"/>    



<bean id="dataSource"
class="org.apache.commons.dbcp.BasicDataSource" destroy-method="close">
<property name="driverClassName" value="${jdbc.driverClassName}"/>
<property name="url" value="${jdbc.url}"/>
<property name="username" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</bean>
<context:property-placeholder location="jdbc.properties"/>


2.C3P0配置:

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<bean id="dataSource"      
        class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">      
    <property name="driverClass" value="${jdbc.driverClassName}"/>      
    <property name="jdbcUrl" value="${jdbc.url}"/>      
    <property name="user" value="${jdbc.username}"/>      
    <property name="password" value="${jdbc.password}"/>      
</bean>       
<context:property-placeholder location="jdbc.properties"/>   



<bean id="dataSource"
class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
<property name="driverClass" value="${jdbc.driverClassName}"/>
<property name="jdbcUrl" value="${jdbc.url}"/>
<property name="user" value="${jdbc.username}"/>
<property name="password" value="${jdbc.password}"/>
</bean>
<context:property-placeholder location="jdbc.properties"/>


3.Druid配置:

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<bean name="dataSource"  
      class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">  
<property name="url" value="${jdbc.url}" />  
<property name="username" value="${jdbc.username}" />  
<property name="password" value="${jdbc.password}" />  
</bean>       
<context:property-placeholder location="jdbc.properties"/>   



<bean name="dataSource"
class="com.alibaba.druid.pool.DruidDataSource" init-method="init" destroy-method="close">
<property name="url" value="${jdbc.url}" />
<property name="username" value="${jdbc.username}" />
<property name="password" value="${jdbc.password}" />
</bean>
<context:property-placeholder location="jdbc.properties"/>
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标签:  面试 java