Java常用基础代码

1.加载properties文件

Properties properties = new Properties(); 

properties.load(Properties.class.getResourceAsStream("/config.properties"));

properties.load(Thread.currentThread().getContextClassLoader().getResourceAsStream("config.properties"));

2.获取绝对路径

${pageContext.request.contextPath} 

 

3.获取路径

HttpServletRequest request = (HttpServletRequest)pageContext.getRequest();

String contextPath=request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+"/";

 

4.运行Junit注解配置

@RunWith(SpringJUnit4ClassRunner.class) // 整合

@ContextConfiguration(locations = "classpath:spring-bean-*.xml") // 加载配置 

 

5.加载spring文件，获取bean

ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
RegisterDAO registerDAO = (RegisterDAO)ac.getBean("RegisterDAO");

ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("classpath:spring/spring.xml");
RedisTemplate redisTemplate = (RedisTemplate)context.getBean("redisTemplate");

如果是两个以上:
ApplicationContext ac = new ClassPathXmlApplicationContext(new String[]{"applicationContext.xml","dao.xml"});

或者用通配符:

ApplicationContext ac = new ClassPathXmlApplicationContext("classpath:/*.xml"); 

6.计算总页码数

(totalCount + pageInfo.getLength() - 1) / pageInfo.getLength()

7.分页算法

pageInfo.setStart((page-1)*pageSize);

8.对URL进行编码

URLDecoder.decode(str,"UTF-8");

URLEncoder.encode(str,"UTF-8");

 

9.将Set集合转为List,这样获得的list并不能有序排列

List<Topic> topicList = new ArrayList<Topic>(user.getTopics());

 

10.将list有序排列 

Collections.sort(topicList, new Comparator<Topic>() {  

   public int compare(Topic arg0, Topic arg1) {  

       return arg0.getTopicId().compareTo(arg1.getTopicId()); // 按照id排列  

   }  

});  

11.CDATA

AND <![CDATA[ (ac.length>= #{start,jdbcType=INTEGER})  ]]>

12.DecimalFormat 

DecimalFormat df = new DecimalFormat("####.00");
Double joinRate=new Double(df.format(temp*100));

13.Spring异常

<!-- 异常处理 -->
<bean class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
<property name="defaultErrorView" value="errorPage/systemError"/> <!-- 默认为500，系统错误(error.jsp) -->
<property name="defaultStatusCode" value="500"/>
<!-- 配置多个statusCode -->
<property name="statusCodes">
<props>
<prop key="500">500</prop>
<prop key="404">404</prop>
</props>
</property>
<property name="exceptionMappings">
<props>
<!-- 这里你可以根据需要定义N多个错误异常转发 -->
<prop key="com.Exception">errorPage/systemError</prop>
<prop key="com.alibaba.dubbo.rpc.RpcException">errorPage/netError</prop>
</props>
</property>
</bean>

 

public static void main(String[] args)throws Exception{
    File file = new File("F:\a.png");
    String a=file.separator;
    System.out.println(a);
    String fileName=file.getName();
    String prefix=fileName.substring(fileName.lastIndexOf("."));
    String datePag = new SimpleDateFormat("yyyyMMdd").format(new Date());
    String ctime = new SimpleDateFormat("yyyyMMddhhmmss").format(new Date());
    System.out.println(ctime);
    System.out.println(prefix);
    String path="D:\"+ctime;
    String pathPag="D:\"+datePag;
    File data = new File(path);
    File dataPag = new File(pathPag);
    if(!dataPag.exists())
        dataPag.mkdirs();
    FileInputStream fis = new FileInputStream(file);
    byte[] b = new byte[1024];
    int len = 0;
    FileOutputStream fos = new FileOutputStream(pathPag+"\"+ctime+prefix);
    while((len=fis.read(b))!=-1){
        fos.write(b,0,len);
    }
    fos.close();
    fis.close();
}