[Spring MVC]之BeanNameViewResolver的用法（自定义View）

BeanNameViewResolver（自定义View）

BeanNameViewResolver这个视图解析器，用于返回自定义的视图。顾名思义，通过配置后，控制器返回自定义的视图的bean名，即可返回自定义的视图。

自定义View

package org.views;

import org.springframework.stereotype.Component;
import org.springframework.web.servlet.View;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.PrintWriter;
import java.util.Map;

@Component("myview")
public class MyView implements View {
    private static final String ContentType = "text/html;charset=utf-8";
	@Override
    public String getContentType() {
        return ContentType;
    }

    @Override
    public void render(Map<String, ?> map,
                       HttpServletRequest httpServletRequest,
                       HttpServletResponse response)
            throws Exception {

        response.setContentType(ContentType);
        PrintWriter writer = response.getWriter();
        map.forEach((k,v)->writer.println(k+" "+v));
        writer.println("<pre>this is bottom</pre>");
    }


}

分析：实现接口View(或者继承AbstractView)，其中方法render实际上跟servlet的service方法功能类似，只不过render方法还传入了模型（model）。@Component("myview")将该视图，声明为框架组件，而且BeanName设置为myview，所以需要将自定义的视图的路径添加到，调度器（dispatcherServlet）配置文件组件扫描标签中，如

<context:component-scan base-package="org.spring;org.spring2;org.views"/>

以上是通过注释的方式，配置自定义视图的使用。由BeanName也可以看出，也可以在配置文件中添加bean的方式实现相同效果,

<bean name="myview" class="org.views.MyView"/>

最后必须提醒，实现接口View时，一定要实现getContentType方法（即使实现了getContentType方法，也别以为是设置了响应体的类型，那你就错了），否则视图解析器将不会返回该视图，原因不明，实测如此。抽象类AbstractView实现了View接口，推荐使用继承抽象类AbstractView取代View接口。

package org.views;

import org.springframework.stereotype.Component;
import org.springframework.web.servlet.view.AbstractView;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.PrintWriter;
import java.util.Map;

@Component("myview")
public class MyView extends AbstractView {
    private static final String ContentType = "text/html;charset=utf-8";

    protected void renderMergedOutputModel(
            Map<String, Object> map,
            HttpServletRequest httpServletRequest,
            HttpServletResponse response
    ) throws Exception {
        response.setContentType(ContentType);
        PrintWriter writer = response.getWriter();
        map.forEach((k,v)->writer.println(k+" "+v));
        writer.println("<pre>this is bottom</pre>");
    }
}

控制器

package org.spring;

import org.springframework.stereotype.Controller;
import org.springframework.ui.ModelMap;
import org.springframework.web.bind.annotation.RequestMapping;


@Controller
public class HelloController {

    @RequestMapping(path = "/hello")
    public String execute(ModelMap modelMap) {
        modelMap.addAttribute(
                "testMessage",
                "<pre>hello huanghaifeng</pre>"
        );
        return "myview";
    }

}

分析：模型添加了一个属性，然后返回自定义视图的BeanName

配置文件

 <bean class="org.springframework.web.servlet.view.ContentNegotiatingViewResolver">
        <property name="viewResolvers">
            <list>
                <bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
                    <property name="prefix" value="/"/>
                    <property name="suffix" value=".jsp"/>
                </bean>
                <bean class="org.springframework.web.servlet.view.BeanNameViewResolver">
                    <property name="order" value="10"/>
                </bean>
            </list>
        </property>
    </bean>

这里，BeanNameViewResolver需要初始化order属性，这样InternalResourceViewResolver"就默认位于视图链的最后。