A, SpringMVC main source analytic process

A, spring mvc features

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1. Review of servlet and jsp execution process

Flow Description:

1. Servlet request
2. Business logic
3. Set Business Model
4. forward jsp Servlet
5. jsp Servlet returns parsed html package

2, spring mvc features

in the spring or essentially the Servlet mvc process, package and simplify the development process, improve ease of use, and using the program logic structure becomes more clearly on the basis thereof

1. Annotation-based URL Xie Ying
2. Form parameter mapping
3. Caching
4. Global unified exception handling
5. Implement Interceptor

3, the request processing flow

4, spring mvc example

For ease of understanding, this gives a simple, minimal spring mvc configuration example:

web.xml servlet configuration:

<servlet>
    <servlet-name>dispatcherServlet</servlet-name>
    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
    <init-param>
        <param-name>contextConfigLocation</param-name>
        <param-value>
            classpath:/spring-mvc.xml
        </param-value>
    </init-param>
</servlet>

<servlet-mapping>
    <servlet-name>dispatcherServlet</servlet-name>
    <url-pattern>/</url-pattern>
</servlet-mapping>
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Written Controller Methods:

public class SimpleController implements Controller {
    @Override
    public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
        ModelAndView modelAndView = new ModelAndView("/WEB-INF/page/userView.jsp");
        modelAndView.addObject("name","cyan");
        return modelAndView;
    }
}
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Configuring spring-mvc.xml file

<bean name="/hello.do" class="com.cyan.controller.SimpleController"></bean>
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The whole process is how to achieve?

1. How dispatchServlet find the corresponding Control?
2. How to perform a business method invocations among Control?

In the interview to answer the above questions is good, we have to figure out spring mvc system components.

Two, mvc architecture Detailed

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1, spring mvc framework to solve the problem

From a technical point of view to think, for any reason an existing framework for their existence, and that reason is to solve practical problems. Or provide a better solution to the problem solution. spring mvc it solves the problem?

1. URL mapping
2. Form parameter mapping
3. Call the target Control
4. Data model mapping
5. View resolution
6. Exception Handling

Solving the above problems are reflected in the spring mvc among the following components:

• Handler Mapping
  • Xie mapping controller url
• Handler Adapter
  • The controller executes adapter
• ViewResolver
  • View warehouse
• view
  • Specific analytical view
• HandlerExceptionResolver
  • Abnormal catcher
• HandlerInterceptor
  • Interceptor

Which corresponds to a specific uml follows:

mvc various components of the implementation process:

2, HandlerMapping Comments

Mvc url path to solve the problem of mapping and Controller image, DispatcherServlet is based on this component to find the corresponding Controller, if not found will be reported No mapping found for HTTP request with URI exception.

HandlerMapping interface structure analysis:

HandlerMapping action is to find the corresponding URL through Handler, but HandlerMapping.getHandler () method does not return directly to the image Handler, but returns to HandlerExecutionChain image, by HandlerExecutionChain.getHandler () returns the final handler

Common implementation class:

The three mainstream mapping as follows:

1. SimpleUrlHandlerMapping: url based on manual configuration and control mapping Xie
2. BeanNameUrlHandlerMapping: ioc name has been based on "/" at the beginning of the line when Bean registration to reflect Xie.
3. RequestMappingHandlerMapping: configuring a corresponding enantiomeric Xie based annotation @RequestMapping

SimpleUrlHandlerMapping :

Written Controller Methods:

public class SimpleHandler implements HttpRequestHandler {

    @Override
    public void handleRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.setAttribute("name","tangtang");
        request.getRequestDispatcher("/WEB-INF/page/userView.jsp").forward(request,response);
    }
}
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Write spring-mvc.xml profile:

<bean id="simpleHandler" class="com.cyan.handler.SimpleHandler"></bean>

<bean class="org.springframework.web.servlet.handler.SimpleUrlHandlerMapping">
    <property name="order" value="100"></property>
    <property name="mappings">
        <props>
            <prop key="hello2.do">simpleHandler</prop>
        </props>
    </property>
</bean>
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SimpleUrlHandlerMapping architecture:

SimpleUrlHandlerMapping key source initialization process:

> org.springframework.web.servlet.handler.SimpleUrlHandlerMapping#setMappings()
> org.springframework.web.servlet.handler.SimpleUrlHandlerMapping#initApplicationContext()
> org.springframework.web.servlet.handler.SimpleUrlHandlerMapping#registerHandlers()
> org.springframework.web.servlet.handler.AbstractUrlHandlerMapping#registerHandler()
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The main processes are: to map the path handler objects (if lazy loading, compared with the bean name) into LinkedHashMap

Get Handler Process Key Source:

> org.springframework.web.servlet.DispatcherServlet#getHandler()
> org.springframework.web.servlet.handler.AbstractHandlerMapping#getHandler()
> org.springframework.web.servlet.handler.AbstractUrlHandlerMapping#getHandlerInternal()
> org.springframework.web.util.UrlPathHelper#getLookupPathForRequest()
> org.springframework.web.util.UrlPathHelper#getPathWithinApplication()

> org.springframework.web.servlet.handler.AbstractUrlHandlerMapping#lookupHandler()

> org.springframework.web.servlet.handler.AbstractHandlerMapping#getHandlerExecutionChain
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Main process: obtaining url path, find Handler, packaging execution chain

BeanNameUrlHandlerMapping :

BeanNameUrlHandlerMapping on a SimpleUrlHandlerMapping to realize, the only difference is inherited from AbstractDetectingUrlHandlerMapping, the handler can be found url mapping configuration in the absence of a case by a corresponding detectHandlers.

Schematic:

RequestMappingHandlerMapping：

Annotation-based implementation, in the following sections explain Xie Ying comment in detail when speaking.

Handler type :

In AbstractUrlHandlerMapping, we can see the storage handler of Map value type is Object, it means that all classes can do to Handler to use?

Handler corresponding type as follows:

• Controller Interface:
• HttpRequestHandler Interface:
• HttpServlet Interface:
• @RequestMapping method Notes

Handler can be seen that there is no unified interface, when dispatchServlet get the current corresponding Handler how to call it? Call it what method? There are two solutions: one is to use instanceof to determine Handler type and then calls related methods. Is achieved by introducing two adapters, each adapter implementation calls the specified Handler (spring latter)

3, HandlerAdapter Detailed

Here spring mvc mode by using an adapter adapted to call the specified Handler, different Adapter Handler depending on the type of which the Handler HandlerAdapter correspondence is as follows:

Handler Class	The corresponding adapter	description
Controller	SimpleControllerHandlerAdapter	Standard controller, return ModelAndView
HttpRequestHandler	HttpRequestHandlerAdapter	Self-service processing request, does not need to view by modelAndView
Servlet	SimpleServletHandlerAdapter	Standards-based servlet processing
Handler Method	RequestMappingHandlerAdapter	The method of processing based on the corresponding @requestMapping

HandlerAdapter interface methods :

FIG HandlerAdapter interface structure :

• The demonstration is based Servlet processing SimpleServletHandlerAdapter

Written Controller Methods:

public class HelloServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
            response.getWriter().println("hello lingqi");
    }

    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }
}
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Write spring-mvc.xml profile:

<bean id="/helloServlet" class="com.cyan.servlet.HelloServlet"></bean>
<bean class="org.springframework.web.servlet.handler.SimpleServletHandlerAdapter"></bean>
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After the above example, when the IOC instantiate classes, corresponding to the DispatcherServlet handler will look through the adapter org.springframework.web.servlet.DispatcherServlet # getHandlerAdapter () method, if no abnormality will be reported as follows: javax.servlet. ServletException: No adapter for handler ......

Gets Adapter Process Key Source:

> org.springframework.web.servlet.DispatcherServlet#getHandlerAdapter()
> 
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4, ViewResolver with View Comments

After finding the corresponding Adapter adapter calls it will be based on business processing, after processing the business side will return a ModelAndView, to find the corresponding view for processing. In () in org.springframework.web.servlet.DispatcherServlet # resolveViewName traverse viewResolvers list to find, if not found it will report a Could not resolve view with name abnormalities.

BeanNameViewResolver example:

Writing a custom view:

public class MyView implements View {
    @Override
    public void render(Map<String, ?> map, HttpServletRequest request, HttpServletResponse response) throws Exception {
        response.getWriter().println("hello "+map.get("name"));
    }

    @Override
    public String getContentType() {
        return null;
    }
}
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Write spring-mvc.xml profile:

<bean name="/myController" class="com.cyan.controller.MyController"></bean>
<bean class="org.springframework.web.servlet.view.BeanNameViewResolver"></bean>
<bean name="myView" class="com.cyan.view.MyView"></bean>
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Written Controller Methods:

public class MyController implements Controller {
    @Override
    public ModelAndView handleRequest(HttpServletRequest httpServletRequest, HttpServletResponse httpServletResponse) throws Exception {
        ModelAndView modelAndView = new ModelAndView("myView");
        modelAndView.addObject("name","qingzi");
        return modelAndView;
    }
}
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InternalResourceViewResolver example:

Write spring-mvc.xml profile:

<bean name="/hello1.do" class="com.cyan.controller.SimpleController"></bean>

<bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/page/"/>
    <property name="suffix" value=".jsp"/>
    <property name="viewClass" value="org.springframework.web.servlet.view.InternalResourceView"/>
</bean>
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Written Controller Methods:

public class SimpleController implements Controller {

    @Override
    public ModelAndView handleRequest(HttpServletRequest request, HttpServletResponse response) throws Exception {
        ModelAndView modelAndView = new ModelAndView("userView");
        modelAndView.addObject("name","cyan");
        return modelAndView;
    }
}
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In the next step is based ViewResolver.resolveViewName () obtains the corresponding View returns to parse and generate Html. VIEW corresponding to the following structure: