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[Java教程]Spring学习(六)—— Spring注解(二)


核心原理

1.       用户发送请求给服务器。url:user.do

2.       服务器收到请求。发现Dispatchservlet可以处理。于是调用DispatchServlet。

3.       DispatchServlet内部,通过HandleMapping检查这个url有没有对应的Controller。如果有,则调用Controller。

4、    Control开始执行

5.       Controller执行完毕后,如果返回字符串,则ViewResolver将字符串转化成相应的视图对象;如果返回ModelAndView对象,该对象本身就包含了视图对象信息。

6.       DispatchServlet将执视图对象中的数据,输出给服务器。

7.       服务器将数据输出给客户端。

spring3.0中相关jar包的含义

 

org.springframework.aop-3.0.3.RELEASE.jar

spring的aop面向切面编程

org.springframework.asm-3.0.3.RELEASE.jar

spring独立的asm字节码生成程序

org.springframework.beans-3.0.3.RELEASE.jar

IOC的基础实现

org.springframework.context-3.0.3.RELEASE.jar

IOC基础上的扩展服务

org.springframework.core-3.0.3.RELEASE.jar

spring的核心包

org.springframework.expression-3.0.3.RELEASE.jar

spring的表达式语言

org.springframework.web-3.0.3.RELEASE.jar

web工具包

org.springframework.web.servlet-3.0.3.RELEASE.jar

mvc工具包

 

 

@Controller控制器定义

和Struts1一样,Spring的Controller是Singleton的。这就意味着会被多个请求线程共享。因此,我们将控制器设计成无状态类。

 

在spring 3.0中,通过@controller标注即可将class定义为一个controller类。为使spring能找到定义为controller的bean,需要在spring-context配置文件中增加如下定义:

 

 

<context:component-scan base-package="com.sxt.web"/>

 

 

         注:实际上,使用@component,也可以起到@Controller同样的作用。

@RequestMapping

 

    在类前面定义,则将url和类绑定。

   在方法前面定义,则将url和类的方法绑定

@RequestParam

         一般用于将指定的请求参数付给方法中形参。示例代码如下:

 

@RequestMapping(params="method=reg5")  public String reg5(@RequestParam("name")String uname,ModelMap map) {    System.out.println("HelloController.handleRequest()");    System.out.println(uname);    return"index";  }

 

    这样,就会将name参数的值付给uname。当然,如果请求参数名称和形参名称保持一致,则不需要这种写法。

@SessionAttributes

    将ModelMap中指定的属性放到session中。示例代码如下:

@Controller@RequestMapping("/user.do")@SessionAttributes({"u","a"})  //将ModelMap中属性名字为u、a的再放入session中。这样,request和session中都有了。publicclass UserController {  @RequestMapping(params="method=reg4")  public String reg4(ModelMap map) {     System.out.println("HelloController.handleRequest()");    map.addAttribute("u","uuuu"); //将u放入request作用域中,这样转发页面也可以取到这个数据。    return"index";  }}

<body>  <h1>**********${requestScope.u.uname}</h1>  <h1>**********${sessionScope.u.uname}</h1> </body>

   

    注:名字为”user”的属性再结合使用注解@SessionAttributes可能会报错。

 

@ModelAttribute

      这个注解可以跟@SessionAttributes配合在一起用。可以将ModelMap中属性的值通过该注解自动赋给指定变量。

    示例代码如下:

 

package com.sxt.web;import javax.annotation.Resource;import org.springframework.stereotype.Controller;import org.springframework.ui.ModelMap;import org.springframework.web.bind.annotation.ModelAttribute;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.SessionAttributes;@Controller@RequestMapping("/user.do")@SessionAttributes({"u","a"}) publicclass UserController {    @RequestMapping(params="method=reg4")  public String reg4(ModelMap map) {    System.out.println("HelloController.handleRequest()");    map.addAttribute("u","尚学堂高淇");    return"index";  }    @RequestMapping(params="method=reg5")public String reg5(@ModelAttribute("u")String uname ,ModelMap map) {    System.out.println("HelloController.handleRequest()");    System.out.println(uname);    return"index";  }  } 

先调用reg4方法,再调用reg5方法。 

Controller类中方法参数的处理

 

Controller类中方法返回值的处理

1.       返回string(建议)

a)         根据返回值找对应的显示页面。路径规则为:prefix前缀+返回值+suffix后缀组成

b)         代码如下:

 

@RequestMapping(params="method=reg4")  public String reg4(ModelMap map) {    System.out.println("HelloController.handleRequest()");    return"index";  }

 

前缀为:/WEB-INF/jsp/    后缀是:.jsp

在转发到:/WEB-INF/jsp/index.jsp

 

2.       也可以返回ModelMap、ModelAndView、map、List、Set、Object、无返回值。一般建议返回字符串!

 

请求转发和重定向

         代码示例:

package com.sxt.web;import javax.annotation.Resource;import org.springframework.stereotype.Controller;import org.springframework.ui.ModelMap;import org.springframework.web.bind.annotation.ModelAttribute;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.SessionAttributes; @Controller@RequestMapping("/user.do")publicclass UserController {    @RequestMapping(params="method=reg4")  public String reg4(ModelMap map) {    System.out.println("HelloController.handleRequest()");//   return "forward:index.jsp";//   return "forward:user.do?method=reg5"; //转发//   return "redirect:user.do?method=reg5"; //重定向    return"redirect:http://www.baidu.com"; //重定向  }    @RequestMapping(params="method=reg5")  public String reg5(String uname,ModelMap map) {    System.out.println("HelloController.handleRequest()");    System.out.println(uname);    return"index";  }  }     

         访问reg4方法,既可以看到效果。

  

获得request对象、session对象

普通的Controller类,示例代码如下:

 

@Controller@RequestMapping("/user.do")publicclass UserController {  @RequestMapping(params="method=reg2")  public String reg2(String uname,HttpServletRequest req,ModelMap map){    req.setAttribute("a", "aa");    req.getSession().setAttribute("b", "bb");    return"index";  }}

ModelMap

         是map的实现,可以在其中存放属性,作用域同request。下面这个示例,我们可以在modelMap中放入数据,然后在forward的页面上显示这些数据。通过el表达式、JSTL、java代码均可。代码如下:

        

package com.sxt.web; import org.springframework.stereotype.Controller;import org.springframework.ui.ModelMap;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.servlet.mvc.multiaction.MultiActionController; @Controller@RequestMapping("/user.do")publicclass UserController extends MultiActionController {    @RequestMapping(params="method=reg")  public String reg(String uname,ModelMap map){    map.put("a", "aaa");    return"index";  }}

<%@ page language="java" import="java.util.*" pageEncoding="gbk"%><%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html> <head></head> <body>    <h1>${requestScope.a}</h1>    <c:out value="${requestScope.a}"></c:out> </body></html>


将属性u的值赋给形参uname




ModelAndView模型视图类

见名知意,从名字上我们可以知道ModelAndView中的Model代表模型,View代表视图。即,这个类把要显示的数据存储到了Model属性中,要跳转的视图信息存储到了view属性。我们看一下ModelAndView的部分源码,即可知其中关系:

[java] view plaincopy 
public class ModelAndView {    /** View instance or view name String */   private Object view;    /** Model Map */   private ModelMap model;    /**   * Indicates whether or not this instance has been cleared with a call to {@link #clear()}.   */   private boolean cleared = false;     /**   * Default constructor for bean-style usage: populating bean   * properties instead of passing in constructor arguments.   * @see #setView(View)   * @see #setViewName(String)   */   public ModelAndView() {   }    /**   * Convenient constructor when there is no model data to expose.   * Can also be used in conjunction with <code>addObject</code>.   * @param viewName name of the View to render, to be resolved   * by the DispatcherServlet's ViewResolver   * @see #addObject   */   public ModelAndView(String viewName) {     this.view = viewName;   }    /**   * Convenient constructor when there is no model data to expose.   * Can also be used in conjunction with <code>addObject</code>.   * @param view View object to render   * @see #addObject   */   public ModelAndView(View view) {     this.view = view;   }    /**   * Creates new ModelAndView given a view name and a model.   * @param viewName name of the View to render, to be resolved   * by the DispatcherServlet's ViewResolver   * @param model Map of model names (Strings) to model objects   * (Objects). Model entries may not be <code>null</code>, but the   * model Map may be <code>null</code> if there is no model data.   */   public ModelAndView(String viewName, Map<String, ?> model) {     this.view = viewName;     if (model != null) {       getModelMap().addAllAttributes(model);     }   }    /**   * Creates new ModelAndView given a View object and a model.   * <emphasis>Note: the supplied model data is copied into the internal   * storage of this class. You should not consider to modify the supplied   * Map after supplying it to this class</emphasis>   * @param view View object to render   * @param model Map of model names (Strings) to model objects   * (Objects). Model entries may not be <code>null</code>, but the   * model Map may be <code>null</code> if there is no model data.   */   public ModelAndView(View view, Map<String, ?> model) {     this.view = view;     if (model != null) {       getModelMap().addAllAttributes(model);     }   }    /**   * Convenient constructor to take a single model object.   * @param viewName name of the View to render, to be resolved   * by the DispatcherServlet's ViewResolver   * @param modelName name of the single entry in the model   * @param modelObject the single model object   */   public ModelAndView(String viewName, String modelName, Object modelObject) {     this.view = viewName;     addObject(modelName, modelObject);   }    /**   * Convenient constructor to take a single model object.   * @param view View object to render   * @param modelName name of the single entry in the model   * @param modelObject the single model object   */   public ModelAndView(View view, String modelName, Object modelObject) {     this.view = view;     addObject(modelName, modelObject);   }     /**   * Set a view name for this ModelAndView, to be resolved by the   * DispatcherServlet via a ViewResolver. Will override any   * pre-existing view name or View.   */   public void setViewName(String viewName) {     this.view = viewName;   }    /**   * Return the view name to be resolved by the DispatcherServlet   * via a ViewResolver, or <code>null</code> if we are using a View object.   */   public String getViewName() {     return (this.view instanceof String ? (String) this.view : null);   }    /**   * Set a View object for this ModelAndView. Will override any   * pre-existing view name or View.   */   public void setView(View view) {     this.view = view;   }    /**   * Return the View object, or <code>null</code> if we are using a view name   * to be resolved by the DispatcherServlet via a ViewResolver.   */   public View getView() {     return (this.view instanceof View ? (View) this.view : null);   }    /**   * Indicate whether or not this <code>ModelAndView</code> has a view, either   * as a view name or as a direct {@link View} instance.   */   public boolean hasView() {     return (this.view != null);   }    /**   * Return whether we use a view reference, i.e. <code>true</code>   * if the view has been specified via a name to be resolved by the   * DispatcherServlet via a ViewResolver.   */   public boolean isReference() {     return (this.view instanceof String);   }    /**   * Return the model map. May return <code>null</code>.   * Called by DispatcherServlet for evaluation of the model.   */   protected Map<String, Object> getModelInternal() {     return this.model;   }    /**   * Return the underlying <code>ModelMap</code> instance (never <code>null</code>).   */   public ModelMap getModelMap() {     if (this.model == null) {       this.model = new ModelMap();     }     return this.model;   }    /**   * Return the model map. Never returns <code>null</code>.   * To be called by application code for modifying the model.   */   public Map<String, Object> getModel() {     return getModelMap();   }     /**   * Add an attribute to the model.   * @param attributeName name of the object to add to the model   * @param attributeValue object to add to the model (never <code>null</code>)   * @see ModelMap#addAttribute(String, Object)   * @see #getModelMap()   */   public ModelAndView addObject(String attributeName, Object attributeValue) {     getModelMap().addAttribute(attributeName, attributeValue);     return this;   }    /**   * Add an attribute to the model using parameter name generation.   * @param attributeValue the object to add to the model (never <code>null</code>)   * @see ModelMap#addAttribute(Object)   * @see #getModelMap()   */   public ModelAndView addObject(Object attributeValue) {     getModelMap().addAttribute(attributeValue);     return this;   }    /**   * Add all attributes contained in the provided Map to the model.   * @param modelMap a Map of attributeName -> attributeValue pairs   * @see ModelMap#addAllAttributes(Map)   * @see #getModelMap()   */   public ModelAndView addAllObjects(Map<String, ?> modelMap) {     getModelMap().addAllAttributes(modelMap);     return this;   }     /**   * Clear the state of this ModelAndView object.   * The object will be empty afterwards.   * <p>Can be used to suppress rendering of a given ModelAndView object   * in the <code>postHandle</code> method of a HandlerInterceptor.   * @see #isEmpty()   * @see HandlerInterceptor#postHandle   */   public void clear() {     this.view = null;     this.model = null;     this.cleared = true;   }    /**   * Return whether this ModelAndView object is empty,   * i.e. whether it does not hold any view and does not contain a model.   */   public boolean isEmpty() {     return (this.view == null && CollectionUtils.isEmpty(this.model));   }    /**   * Return whether this ModelAndView object is empty as a result of a call to {@link #clear}   * i.e. whether it does not hold any view and does not contain a model.   * <p>Returns <code>false</code> if any additional state was added to the instance   * <strong>after</strong> the call to {@link #clear}.   * @see #clear()   */   public boolean wasCleared() {     return (this.cleared && isEmpty());   }     /**   * Return diagnostic information about this model and view.   */   @Override   public String toString() {     StringBuilder sb = new StringBuilder("ModelAndView: ");     if (isReference()) {       sb.append("reference to view with name '").append(this.view).append("'");     }     else {       sb.append("materialized View is [").append(this.view).append(']');     }     sb.append("; model is ").append(this.model);     return sb.toString();   } } 






 

[java] view plaincopy
测试代码如下:
package com.sxt.web;  import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.servlet.ModelAndView; import org.springframework.web.servlet.mvc.multiaction.MultiActionController;  import com.sxt.po.User;  @Controller @RequestMapping("/user.do") public class UserController extends MultiActionController {      @RequestMapping(params="method=reg")   public ModelAndView reg(String uname){     ModelAndView mv = new ModelAndView();     mv.setViewName("index"); //   mv.setView(new RedirectView("index"));          User u = new User();     u.setUname("高淇");     mv.addObject(u);  //查看源代码,得知,直接放入对象。属性名为”首字母小写的类名”。 一般建议手动增加属性名称。     mv.addObject("a", "aaaa");     return mv;   }  } <%@ page language="java" import="java.util.*" pageEncoding="gbk"%> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html>  <head>  </head>  <body>     <h1>${requestScope.a}</h1>     <h1>${requestScope.user.uname}</h1>  </body> </html> 

地址栏输入:http://localhost:8080/springmvc03/user.do?method=reg