java(三)

空判断

list == null || list.isEmpty()

isNull()和containsKey()使用场景

如何判断json里面某个key存不存在org.json.JSONObject的!json.isNull("XXX") net.sf.json.JSONObject的json.containsKey("XXX") 

查看后台的logs情况

cd logstail -f catalina.out(运行后，相当于console)sz catalina.out

Java web 框架：
web.xml：

<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" id="WebApp_ID" version="2.5">    <display-name>xxxx</display-name>    <context-param>        <param-name>contextConfigLocation</param-name>        <param-value>classpath:spring/applicationContext*.xml</param-value>    </context-param>    <!--Spring的ApplicationContext 载入 -->    <listener>        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>    </listener>    <!-- 编码过滤器，以UTF8编码 -->    <filter>        <filter-name>encodingFilter</filter-name>        <filter-class>org.springframework.web.filter.CharacterEncodingFilter</filter-class>        <init-param>            <param-name>encoding</param-name>            <param-value>UTF8</param-value>        </init-param>    </filter>    <filter-mapping>        <filter-name>encodingFilter</filter-name>        <url-pattern>/*</url-pattern>    </filter-mapping>    <!-- 配置SpringMVC框架入口 -->    <servlet>        <servlet-name>xxx</servlet-name>        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>        <load-on-startup>1</load-on-startup>        <init-param>            <param-name>contextConfigLocation</param-name>            <param-value>classpath:xxx.xml</param-value>        </init-param>    </servlet>    <servlet-mapping>        <servlet-name>xxx</servlet-name>        <url-pattern>/rest/*</url-pattern>    </servlet-mapping>    <welcome-file-list>        <welcome-file>index.html</welcome-file>    </welcome-file-list></web-app>

Mapper（模板）.xml

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="cn.mapper.UserMapper"></mapper>

log4j.properties

log4j.rootLogger=DEBUG,A1log4j.logger.com.taotao = DEBUGlog4j.logger.org.mybatis = DEBUGlog4j.appender.A1=org.apache.log4j.ConsoleAppenderlog4j.appender.A1.layout=org.apache.log4j.PatternLayoutlog4j.appender.A1.layout.ConversionPattern=%-d{yyyy-MM-dd HH:mm:ss,SSS} [%t] [%c]-[%p] %m%n

mybatis-config（模板）.xml

<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE configuration  PUBLIC "-//mybatis.org//DTD Config 3.0//EN"  "http://mybatis.org/dtd/mybatis-3-config.dtd"><configuration>    <properties resource="jdbc.properties" />    <typeAliases>        <!-- 设置别名 -->        <package name="cn.mybatis.pojo" />    </typeAliases>    <!-- 配置数据库连接的环境 -->    <environments default="development">        <environment id="development">            <transactionManager type="JDBC" />            <dataSource type="POOLED">                <property name="driver" value="${jdbc.driver}" />                <property name="url" value="${jdbc.url}" />                <property name="username" value="${jdbc.username}" />                <property name="password" value="${jdbc.password}" />            </dataSource>        </environment>    </environments>    <mappers>        <package name="cn.mybatis.mapper" />    </mappers></configuration>

SpringMVC（模板）.xml

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"    xmlns:context="http://www.springframework.org/schema/context"    xmlns:mvc="http://www.springframework.org/schema/mvc"    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-4.0.xsd        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd"></beans>

applicationContext.xml

<beans xmlns="http://www.springframework.org/schema/beans"    xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd    http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd    http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd">    <!-- 使用spring自带的占位符替换功能 -->    <bean        class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">        <!-- 允许JVM参数覆盖 -->        <property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE" />        <!-- 忽略没有找到的资源文件 -->        <property name="ignoreResourceNotFound" value="true" />        <!-- 配置资源文件 -->        <property name="locations">            <list>                <value>classpath:xxxx.properties</value>            </list>        </property>    </bean>    <!-- 扫描包 -->    <context:component-scan base-package="com.taotao"/>     <!-- 定义数据源 -->    <bean id="dataSource" class="com.jolbox.bonecp.BoneCPDataSource"        destroy-method="close">        <!-- 数据库驱动 -->        <property name="driverClass" value="${jdbc.driver}" />        <!-- 相应驱动的jdbcUrl -->        <property name="jdbcUrl" value="${jdbc.url}" />        <!-- 数据库的用户名 -->        <property name="username" value="${jdbc.username}" />        <!-- 数据库的密码 -->        <property name="password" value="${jdbc.password}" />        <!-- 检查数据库连接池中空闲连接的间隔时间，单位是分，默认值：240，如果要取消则设置为0 -->        <property name="idleConnectionTestPeriod" value="60" />        <!-- 连接池中未使用的链接最大存活时间，单位是分，默认值：60，如果要永远存活设置为0 -->        <property name="idleMaxAge" value="30" />        <!-- 每个分区最大的连接数 -->        <!--             判断依据：请求并发数         -->        <property name="maxConnectionsPerPartition" value="100" />        <!-- 每个分区最小的连接数 -->        <property name="minConnectionsPerPartition" value="5" />    </bean></beans>

jdbc.properties

jdbc.driverClassName=com.mysql.jdbc.Driverjdbc.url=jdbc:mysql://127.0.0.1:3306/taotao?useUnicode=true&characterEncoding=utf8&autoReconnect=true&allowMultiQueries=truejdbc.username=rootjdbc.password=123456

applicationContext-transaction.xml

<beans xmlns="http://www.springframework.org/schema/beans"    xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"    xmlns:aop="http://www.springframework.org/schema/aop" xmlns:tx="http://www.springframework.org/schema/tx"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd    http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.0.xsd    http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop-4.0.xsd http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-4.0.xsd    http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-4.0.xsd">    <!-- 定义事务管理器 -->    <bean id="transactionManager"        class="org.springframework.jdbc.datasource.DataSourceTransactionManager">        <property name="dataSource" ref="dataSource" />    </bean>    <!-- 定义事务策略 -->    <tx:advice id="txAdvice" transaction-manager="transactionManager">        <tx:attributes>            <!--所有以query开头的方法都是只读的 -->            <tx:method name="query*" read-only="true" />            <!--其他方法使用默认事务策略 -->            <tx:method name="*" />        </tx:attributes>    </tx:advice>    <aop:config>        <!--pointcut元素定义一个切入点，execution中的第一个星号 用以匹配方法的返回类型，            这里星号表明匹配所有返回类型。 com.abc.dao.*.*(..)表明匹配cn.itcast.mybatis.service包下的所有类的所有             方法 -->        <aop:pointcut id="myPointcut" expression="execution(* cn.itcast.mybatis.service.*.*(..))" />        <!--将定义好的事务处理策略应用到上述的切入点 -->        <aop:advisor advice-ref="txAdvice" pointcut-ref="myPointcut" />    </aop:config></beans>