單例模式

//讀取配置文件的工具類-單例模式
public class ConfigManager {
    private static Properties properties;
    private static ConfigManager configManager;

    // 私有構造器-讀取數據庫配置文件
    private ConfigManager() {
        properties = new Properties();
        String configFile = "database.properties";
        InputStream is 
 
= ConfigManager.class.getClassLoader()
                .getResourceAsStream(configFile);
        try {
            properties.load(is);
            is.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    // 全局訪問點
    public static ConfigManager getInstance() {
        
 
if (configManager == null) {
            configManager = new ConfigManager();
        }
        return configManager;
    }

    public String getValue(String key) {
        return properties.getProperty(key);
    }

}

　懶漢模式

　餓漢模式

Spring MVC-Controller的單例管理

搭建超市訂單管理系統的配置文件

　applicationContext-jdbc.xml

<!-- 使spring掃描包下的所有類，讓標註spring註解的類生效 
        若掃描到有@Component @Controller @Service等這些註解的類，則把這些類註冊為bean -->
<context:component-scan base-package="cn.smbms.service"/> 
<context:component-scan base-package="cn.smbms.dao"/>

　springmvc-servlet.xml

<!-- 控制器的掃描 -->                                                                      
<context:component-scan base-package="cn.smbms.controller"/>                         
<mvc:annotation-driven/>                                                             
                                                                                     
<!-- 靜態資源文件的引入 -->                                                                   
<mvc:resources location="/statics/" mapping="/statics/**"/>                          
                                                                                     
<!-- 視圖解析：prefix：前綴，suffix：後綴 -->                                                    
<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">     
    <property name="prefix" value="/WEB-INF/jsp/"/>                                  
    <property name="suffix" value=".jsp"/>                                           
</bean>                                                                              
                                                                                     
<!-- 全局異常 -->                                                                        
<bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
    <property name="exceptionMappings">                                              
        <props>                                                                      
            <prop key="java.lang.RuntimeException">error</prop>                      
        </props>                                                                     
    </property>                                                                      
</bean>                                                                              

　web.xml

<!-- log4j config path -->                                                                
<context-param>                                                                           
    <param-name>log4jConfigLocation</param-name>                                          
    <param-value>classpath:log4j.properties</param-value>                                 
</context-param>                                                                          
<!-- webapp root path -->                                                                 
<context-param>                                                                           
    <param-name>webAppRootKey</param-name>                                                
    <param-value>SMBMS.root</param-value>                                                 
</context-param>                                                                          
<!-- Spring相關的配置 -->                                                                      
<context-param>                                                                           
    <param-name>contextConfigLocation</param-name>                                        
    <param-value>classpath:applicationContext-*.xml</param-value>                         
</context-param>                                                                          
                                                                                          
<!-- 監聽器 -->                                                                              
<listener>                                                                                
    <listener-class>org.springframework.web.util.Log4jConfigListener</listener-class>     
</listener>                                                                               
<!-- 初始化Spring容器 -->                                                                      
<listener>                                                                                
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>                                                                               
                                                                                          
<!-- 字符編碼過濾器 -->                                                                          
<filter>                                                                                  
    <filter-name>encodingFilter</filter-name>                                             
    <filter-class>                                                                        
        org.springframework.web.filter.CharacterEncodingFilter                            
    </filter-class>                                                                       
    <init-param>                                                                          
        <param-name>encoding</param-name>                                                 
        <param-value>UTF-8</param-value>                                                  
    </init-param>                                                                         
    <init-param>                                                                          
        <!-- 強制編碼格式 -->                                                                   
        <param-name>forceEncoding</param-name>                                            
        <param-value>true</param-value>                                                   
    </init-param>                                                                         
</filter>                                                                                 
<filter-mapping>                                                                          
    <filter-name>encodingFilter</filter-name>                                             
    <url-pattern>/*</url-pattern>                                                         
</filter-mapping>                                                                         
                                                                                          
<!-- 配置Servlet -->                                                                        
<servlet>                                                                                 
    <servlet-name>springmvc</servlet-name>                                                
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>      
    <init-param>                                                                          
        <param-name>contextConfigLocation</param-name>                                    
        <param-value>classpath:springmvc-servlet.xml</param-value>                        
    </init-param>                                                                         
    <load-on-startup>1</load-on-startup>                                                  
</servlet>                                                                                
<servlet-mapping>                                                                         
    <servlet-name>springmvc</servlet-name>                                                
    <url-pattern>/</url-pattern>                                                          
</servlet-mapping>                                                                        

單例模式及搭建配置文件