Spring开发指南读书笔记（一）

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Spring给程序员提供了一个轻量级的构建技术框架。它主要的特性就是控制反转IOC和面向切面AOP编程。

它的作用是使用基本的Bean来完成EJB可以完成的工作，提高了代码的可重用性，简单、松耦合和可测试性。

一个简单的Spring例子：

public interface Action {

public String execute(String str);
}

实现类：

public class LowerAction implements Action{

private String message;

public String getMessage() {
return message;
}

public void setMessage(String message) {
this.message = message;
}

public String execute(String str) {
return (getMessage()+str).toLowerCase();
}
}

spring配置文件：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
<bean id="TheAction" class ="com.spring.LowerAction">
  <property name="message">
   <value>Hello</value>
  </property>
</bean>
</beans>

测试：

public void testQickStart(){
  ApplicationContext ctx=new FileSystemXmlApplicationContext("bean.xml");
  Action action=(Action)ctx.getBean("TheAction");
  System.out.println(action.execute("Jeff Cheng"));
}

在spring中的依赖注入有3种实现类型：接口注入、设值注入和构造子注入。所谓依赖注入，就是在运行期由容器将依赖关系注入到组件之中。而程序员只须负责对接口的编程而不必理会接口具体是如何实现的。

一个完整的Bean配置

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
<description>Spring Bean Configuration Sample</description>
<bean id="TheAction"
  class="com.spring.UpperAction"
  singleton="true"                                        //是否采用单例
  init-method="init"
  destroy-method="cleanup"
  depends-on="ActionManager">                //是否依赖其他Bean
  <property name="message">
   <value>HeLLo</value>
  </property>
  <property name="dataSource">
   <ref local="dataSource"/>                       //指定属性对其他Bean的引用关系
  </property>
</bean>

<bean id="dataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
  <property name="jndiName">
   <value>java:comp/env/jdbc/sample</value>
  </property>
</bean>
</beans>

测试代码：

BeanFactory提供了针对Java Bean的管理功能，而ApplicationContext覆盖了BeanFactory的全部功能并提供了更为框架的实现。

1.国际化支持：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>

<bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
               
  <property name="basenames">
   <list>
    <value>messages</value>
   </list>
  </property>
</bean>
</beans>

Spring会自动在classpath路径中搜索配置文件加载：

messages_zh_CN.properties，messages_zh.properties，message.properties

2.资源访问：Application.getResource("...")；

3.事件传播：

可以通过设置listener实现

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>
<description>Spring Login Action</description>
<bean id="loginaction" class ="com.spring.LoginAction"/>
<bean id="listener" class="com.spring.ActionListener"/>
</beans>

LoginAction.java：

public class LoginAction implements ApplicationContextAware{
private ApplicationContext applicationContext;

public void setApplicationContext(ApplicationContext applicationContext)
   throws BeansException {
   this.applicationContext=applicationContext;
}
  public int login(String username,String password){
  ActionEvent event=new ActionEvent(username);
  this.applicationContext.publishEvent(event);
  System.out.println("finish");
  return 0;
}
}

ActionListenser.java：

public class ActionListener implements ApplicationListener{

public void onApplicationEvent(ApplicationEvent event) {
  if(event instanceof ActionEvent){
   System.out.println(event.toString());
  }
}
}

ActionEvent.java：

public class ActionEvent extends ApplicationEvent{

public ActionEvent(Object source) {
super(source);
}
}

测试类：

public void testLoginAction(){
  ApplicationContext ctx=new FileSystemXmlApplicationContext("loginBean.xml");
  LoginAction action=(LoginAction)ctx.getBean("loginaction");
  action.login("Jeff Cheng", "mypass");
}

对于web应用，我们可以在web.xml中配置ContextLoaderListener或ContextLoderServlet

<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>

</listener>

或

<servlet>
  <servlet-name>context</servlet-name>
  <servlet-class>org.springframework.web.context.ContextLoaderServlet</servlet-class>
  <load-on-startup>1</load-on-startup>
</servlet>

Spring高级特性：与MVC框架的整合

MVC框架的运作流程：

1.将Web页面中的输入元素封装成一个请求数据对象。

2.根据请求不同，调度相应的逻辑处理单元，并将请求数据对象作为参数传入。

3.逻辑单元完成运算后，返回一个结果对象。

4.将结果数据对象中的数据与预先设计的表现层相融合并展现给用户。

Struts：成熟的设计，丰富的资源和开发群体
Webwork2：设计理念更加先进，代码与Servlet API分离，单元测试便利，BS与CS转换方便，基于对模板技术(Velocity、FreeMarker和XSLT)的支持。
SpringMVC：在依赖注入和AOP方面更加优秀，但MVC框架与底层框架的分离不如webwork，难以脱离servlet容器独立运行。

首先来看看与SpringMVC的搭配：

web.xml容器配置文件
<servlet>
<servlet-name>Dispatcher</servlet-name>
<servlet-class>

org.springframework.web.servlet.DispatcherServlet //负责调度的核心引擎

</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/Config.xml</param-value>
</init-param>
</servlet>
<servlet-mapping>
<servlet-name>Dispatcher</servlet-name>
<url-pattern>*.do</url-pattern>
</servlet-mapping>

spring核心配置文件：
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>

<bean id="viewResolver" class ="org.springframework.web.servlet.view.InternalResourceViewResolver">
                       
  <property name="viewClass">
   <value>org.springframework.web.servlet.view.JstlView</value>
  </property>

  <property name="prefix">                   //设定名称前缀
   <value>WEB-INF/view/</value>
  </property>

  <property name="suffix">                   //设定名称后缀
   <value>.jsp</value>
  </property>
</bean>

<bean id="RegisterValidator" class="com.validator.RegisterValidator"/>


<bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
  <property name="mappings">
   <props>
    <prop key="/register.do">RegisterAction</prop>
    <prop key="/login.do">LoginAction</prop>
   </props>
  </property>
</bean>


<bean id="RegisterAction" class="com.action.RegisterAction">
  <property name="commandClass">
   <value>com.reqbean.RegisterInfo</value>
  </property>

  <property name="validator">
   <ref local="RegisterValidator"/>
  </property>

  <property name="formView">
   <value>register</value>
  </property>

  <property name="successView">
   <value>RegisterSuccess</value>
  </property>
</bean>

<bean id="LoginAction" class="com.action.LoginAction">
  <property name="commandClass">
   <value>com.action.LoginInfo</value>
  </property>

  <property name="fail_view">
   <value>loginfail</value>
  </property>

  <property name="success_view">
   <value>main</value>
  </property>
</bean>


<bean id="exceptionResolver" class="org.springframework.web.servlet.handler.SimpleMappingExceptionResolver">
  <property name="defaultErrorView">
   <value>failure</value>
  </property>

  <property name="exceptionMappings">
   <props>
    <prop key="java.sql.SQLException">showDBError</prop>
    <prop key="java.lang.RuntimeException">showError</prop>
   </props>
  </property>
</bean>


<bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
  <property name="basename">
   <value>messages</value>
  </property>
</bean>

<bean id="localeResolver" class="org.springframework.web.servlet.i18n.AcceptHeaderLocaleResolver">
</bean>


</beans>

LoginAction.java：

public class LoginAction extends SimpleFormController{

private String fail_view;
private String success_view;

protected ModelAndView onSubmit(Object cmd,BindException ex)throws Exception{
  LoginInfo loginInfo=(LoginInfo)cmd;

  if(login(loginInfo)==0){
   HashMap result_map=new HashMap();
   result_map.put("logininfo", loginInfo);
   List msgList=new LinkedList();
   msgList.add("msg1");
   msgList.add("msg2");
   msgList.add("msg3");

   result_map.put("messages", msgList);
   return new ModelAndView(this.getSuccess_view(),result_map);
  }else{
   return new ModelAndView(this.getFail_view());
  }
}

private int login(LoginInfo loginInfo){
  if("JeffCheng".equalsIgnoreCase(loginInfo.getUsername())
    &&"123".equals(loginInfo.getPassword())){
   return 0;
  }
  return 1;
}

public String getFail_view(){
  return fail_view;
}

public String getSuccess_view(){
  return success_view;
}

public void setFail_view(String fail_view) {
  this.fail_view = fail_view;
}

public void setSuccess_view(String success_view) {
this.success_view = success_view;
}

}

RegisterAction.java：

public class RegisterAction extends SimpleFormController{

protected ModelAndView onSubmit(Object cmd, BindException ex)
   throws Exception {
  Map rsMap=new HashMap();
  rsMap.put("logininfo", cmd);
  return new ModelAndView(this.getSuccessView(), rsMap);
}
}
RegisterValidator.java：

public class RegisterValidator implements Validator{

public boolean supports(Class clazz) {
return RegisterInfo.class.isAssignableFrom(clazz);
}

public void validate(Object obj, Errors errors) {
  RegisterInfo regInfo=(RegisterInfo)obj;
  if(regInfo.getUsername().length()<4){
   errors.rejectValue("username","less4chars",null,"用户名长度必须大于4个字母!");
  }
  /*检查用户名是否已经存在
  if(UserDao.getUser(regInfo.getUsername())!=null){
   errors.rejectValue("username","existed",null,"用户已存在");
  }
  */
  if(regInfo.getPassword1().length()<6){
   errors.rejectValue("password1","less6chars",null,"密码长度必须大于6个字母!");
  }
  if(!regInfo.getPassword2().equals(regInfo.getPassword1())){
   errors.rejectValue("password2","notsame",null,"两次输入密码不一致!");
  }
}
}

RegisterInfo.java：

public class RegisterInfo {
private String username;
private String password1;
private String password2;

public String getUsername() {
  return username;
}
public void setUsername(String username) {
  this.username = username;
}
public String getPassword1() {
  return password1;
}
public void setPassword1(String password) {
  this.password1 = password;
}

public String getPassword2() {
  return password2;
}
public void setPassword2(String password) {
  this.password2 = password;
}
}

LoginInfo.java：

public class LoginInfo {
private String username;
private String password;

public String getUsername() {
  return username;
}
public void setUsername(String username) {
  this.username = username;
}
public String getPassword() {
  return password;
}
public void setPassword(String password) {
  this.password = password;
}
}

main.jsp：

<%@ taglib uri="http://java.sun.com/jstl/core" prefix="c"%>

<body>
<p>Login Success!</p>
<p>Current User:
<c:out value="${logininfo.username}" /><br>
</p>

<p>Your current messages:</p>
<c:forEach items="${messages}" var="item" begin="0" end="9" step="1" varStatus="var">
  <c:choose>
   <c:when test="${var.index%2==0}">
   *
   </c:when>
   <c:otherwise>
   !
   </c:otherwise>
  </c:choose>
  <c:out value="${item}" /><br>
</c:forEach>
</body>

register.jsp：

<%@ taglib uri="http://java.sun.com/jstl/core" prefix="c"%>
<%@ taglib uri="http://www.springframework.org/tags" prefix="spring"%>

  </table>
<p>
  <input type="submit" value="提交" name="B1">
  <input type="reset" value="重置" name="B2">
</p>
</form>
</body>

RegisterSuccess.jsp：

showError.jsp：

<body>
<%Exception ex=(Exception)request.getAttribute("Exception"); %>
<h2>Exception:<%ex.getMessage(); %></h2>
<p/>
<%ex.printStackTrace(new java.io.PrintWriter(out)); %>
</body>

模版技术：

XSLT：基于XML的表现层模版技术，移植性强，界面开发难度大，语法复杂，调试难度大，性能比较低下，内存占用较大
Velocity：最为成熟的模版技术，得到广泛的应用。
FreeMarker：表现逻辑和业务逻辑划分严格，模板不允许对Servlet API直接操作，禁止对HttpServletRequest对象直接访问，保证了层次间的清晰。提供了对JSP Tag的良好的支持，在生产效率和学习成本上具有优势。

下面用FreeMarker来改造上面的例子：

Config.xml：

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd">
<beans>

<bean id="viewResolver" class ="org.springframework.web.servlet.view.freemarker.FreeMarkerViewResolver">
  <property name="viewClass">
   <value>org.springframework.web.servlet.view.freemarker.FreeMarkerView</value>
  </property>

  <property name="cache">
   <value>false</value>
  </property>

  <property name="suffix">
   <value>.ftl</value>
  </property>
</bean>

<bean id="freemarkerConfig" class="org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer">
  <property name="templateLoaderPath">
   <value>WEB-INF/view/</value>
  </property>
</bean>


<bean id="urlMapping" class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
  <property name="mappings">
   <props>
    <prop key="/login.do">LoginAction</prop>
   </props>
  </property>
</bean>


<bean id="LoginAction" class="com.action.LoginAction">
  <property name="commandClass">
   <value>com.action.LoginInfo</value>
  </property>

  <property name="fail_view">
   <value>loginfail</value>
  </property>

  <property name="success_view">
   <value>main</value>
  </property>
</bean>
</beans>

main.ftl：

<html>
<head>
<title>Welcome!</title>
</head>
<body>
<h1>Current User:${logininfo.username}</h1>
<#list messages as msg>
  <#if msg_index%2=0>
   *
  <#else>
   !
  </#if>
  ${msg}<br>
</#list>
</body>
</html>