Spring4 MVC ContentNegotiatingViewResolver多种输出格式实例

本文演示支持多种输出格式，这里 Spring4%uA0MVC应用程序使用了%uA0Spring%uA0ContentNegotiatingViewResolver%uA0。我们将生成应用程序输出XML，JSON，PDF，XLS和HTML格式，全部采用基于注解配置的。

ContentNegotiatingViewResolver是 ViewResolver 使用所请求的媒体类型的一个实现(基于文件类型扩展，输出格式URL参数指定类型或接受报头)来选择一个合适的视图一个请求。ContentNegotiatingViewResolver本身并不解决视图，只不表示为其他的 ViewResolver，您可以配置来处理特定的视图(XML，JSON，PDF，XLS，HTML，..)。

这里需要使用到以下技术：

Spring 4.0.6.RELEASE
jackson-databind 2.4.1.3
jackson-annotations 2.4.1
lowagie itext 4.2.1
Apache POI 3.10-beta2
Maven 3
JDK 1.6
Tomcat 7.0.54
Eclipse JUNO Service Release 2

我们现在就开始！

第1步：创建目录结构

以下将是本实例的最终目录结构：

我们将使用Spring%uA0Java配置(注释)。现在，让我们来添加/更新上述项目结构中提到的内容。

第2步：用所需的依赖更新 pom.xml

<?xml version="1.0"?>
<project
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
	xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">

	<modelVersion>4.0.0</modelVersion>
	<groupId>com.yiibai.springmvc</groupId>
	<artifactId>ContentNegotiatingViewResolver</artifactId> <packaging>war</packaging>
	<version>1.0.0</version>
	<name>Spring4MVCContentNegotiatingViewResolverExample</name>

	<properties>
		<springframework.version>4.0.6.RELEASE</springframework.version>
	</properties>

	<dependencies>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-core</artifactId>
			<version>${springframework.version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-web</artifactId>
			<version>${springframework.version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>${springframework.version}</version>
		</dependency>

		<!-- Needed for XML View (with JAXB2) -->
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-oxm</artifactId>
			<version>${springframework.version}</version>
		</dependency>

		<!-- Needed for JSON View -->
		<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-databind</artifactId>
			<version>2.4.1.3</version>
		</dependency>
		<dependency>
			<groupId>com.fasterxml.jackson.core</groupId>
			<artifactId>jackson-annotations</artifactId>
			<version>2.4.1</version>
		</dependency>

		<!-- Needed for PDF View -->
		<dependency>
			<groupId>com.lowagie</groupId>
			<artifactId>itext</artifactId>
			<version>4.2.1</version>
		</dependency>
		
		<!-- Needed for XLS View -->		
		<dependency>
			<groupId>org.apache.poi</groupId>
			<artifactId>poi</artifactId>
			<version>3.10-beta2</version>
		</dependency>

		<!-- Servlet dependencies -->
		<dependency>
			<groupId>javax.servlet</groupId>
			<artifactId>javax.servlet-api</artifactId>
			<version>3.1.0</version>
		</dependency>
		<dependency>
		    <groupId>javax.servlet</groupId>
		    <artifactId>jstl</artifactId>
		    <version>1.2</version>
		</dependency>
		<dependency>
			<groupId>javax.servlet.jsp</groupId>
			<artifactId>javax.servlet.jsp-api</artifactId>
			<version>2.3.1</version>
		</dependency>

	</dependencies>


	<build>
		<pluginManagement>
			<plugins>
				<plugin>
					<groupId>org.apache.maven.plugins</groupId>
					<artifactId>maven-war-plugin</artifactId>
					<version>2.4</version>
					<configuration>
						<warSourceDirectory>src/main/webapp</warSourceDirectory>
						<warName>ContentNegotiatingViewResolver</warName> <failOnMissingWebXml>false</failOnMissingWebXml>
					</configuration>
				</plugin>
			</plugins>
		</pluginManagement>

		<finalName>ContentNegotiatingViewResolver</finalName> </build>
</project>
%uA0

上面解析 PDF 的依赖库有点问题，可修改为以下测试构建就没有问题：

 <dependency>
             <groupId>com.lowagie</groupId>
          <artifactId>itext</artifactId>
          <version>2.1.7</version>
          <scope>compile</scope>
        </dependency>

spring-oxm是为了支持XML输出生成(使用JAXB2)。%uA0jackson-databind%uA0&jackson-annotations%uA0提供JSON输出支持。iText的提供PDF生成库，支持PDF输出。%uA0Apache%uA0POI将有助于产生XLS输出格式。

第3步：创建Spring配置文件类

com.yiibai.springmvc.configuration.AppConfig

package com.yiibai.springmvc.configuration

import java.util.ArrayList
import java.util.List

import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.ComponentScan
import org.springframework.context.annotation.Configuration
import org.springframework.http.MediaType
import org.springframework.oxm.jaxb.Jaxb2Marshaller
import org.springframework.web.accept.ContentNegotiationManager
import org.springframework.web.servlet.ViewResolver
import org.springframework.web.servlet.config.annotation.ContentNegotiationConfigurer
import org.springframework.web.servlet.config.annotation.EnableWebMvc
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter
import org.springframework.web.servlet.view.ContentNegotiatingViewResolver
import org.springframework.web.servlet.view.InternalResourceViewResolver
import org.springframework.web.servlet.view.JstlView

import com.yiibai.springmvc.model.Pizza
import com.yiibai.springmvc.viewresolver.ExcelViewResolver
import com.yiibai.springmvc.viewresolver.JsonViewResolver
import com.yiibai.springmvc.viewresolver.Jaxb2MarshallingXmlViewResolver
import com.yiibai.springmvc.viewresolver.PdfViewResolver

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = "com.yiibai.springmvc")
public class AppConfig extends WebMvcConfigurerAdapter {

	/*
	 * Configure ContentNegotiationManager
	 */
	@Override
	public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
		configurer.ignoreAcceptHeader(true).defaultContentType(
				MediaType.TEXT_HTML)
	}

	/*
	 * Configure ContentNegotiatingViewResolver
	 */
	@Bean
	public ViewResolver contentNegotiatingViewResolver(ContentNegotiationManager manager) {
		ContentNegotiatingViewResolver resolver = new ContentNegotiatingViewResolver()
		resolver.setContentNegotiationManager(manager)

		// Define all possible view resolvers
		List<ViewResolver> resolvers = new ArrayList<ViewResolver>()

		resolvers.add(jaxb2MarshallingXmlViewResolver())
		resolvers.add(jsonViewResolver())
		resolvers.add(jspViewResolver())
		resolvers.add(pdfViewResolver())
		resolvers.add(excelViewResolver())
		
		resolver.setViewResolvers(resolvers)
		return resolver
	}

	/*
	 * Configure View resolver to provide XML output Uses JAXB2 marshaller to
	 * marshall/unmarshall POJO&aposs (with JAXB annotations) to XML
	 */
	@Bean
	public ViewResolver jaxb2MarshallingXmlViewResolver() {
		Jaxb2Marshaller marshaller = new Jaxb2Marshaller()
		marshaller.setClassesToBeBound(Pizza.class)
		return new Jaxb2MarshallingXmlViewResolver(marshaller)
	}

	/*
	 * Configure View resolver to provide JSON output using JACKSON library to
	 * convert object in JSON format.
	 */
	@Bean
	public ViewResolver jsonViewResolver() {
		return new JsonViewResolver()
	}

	/*
	 * Configure View resolver to provide PDF output using lowagie pdf library to
	 * generate PDF output for an object content
	 */
	@Bean
	public ViewResolver pdfViewResolver() {
		return new PdfViewResolver()
	}

	/*
	 * Configure View resolver to provide XLS output using Apache POI library to
	 * generate XLS output for an object content
	 */
	@Bean
	public ViewResolver excelViewResolver() {
		return new ExcelViewResolver()
	}

	/*
	 * Configure View resolver to provide HTML output This is the default format
	 * in absence of any type suffix.
	 */
	@Bean
	public ViewResolver jspViewResolver() {
		InternalResourceViewResolver viewResolver = new InternalResourceViewResolver()
		viewResolver.setViewClass(JstlView.class)
		viewResolver.setPrefix("/WEB-INF/views/")
		viewResolver.setSuffix(".jsp")
		return viewResolver
	}

}

让我们来讨论说明上面的类的详细信息：

第一步是建立它用于通过委托给ContentNegotiationManager，以确定所请求的媒体类型的请求是%uA0ContentNegotiationStrategy%uA0列表的一个实例。默认情况下PathExtensionContentNegotiationStrategy被查询(使用URL扩展名，例如. .xls, .pdf,.json.)，接着ParameterContentNegotiationStrategy(使用请求参数%uA0‘format=xls’，例如)，其次是HeaderContentNegotiationStrategy(使用HTTP接受头)。

	public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
		configurer.ignoreAcceptHeader(true).defaultContentType(
				MediaType.TEXT_HTML)
	}
%uA0

在我们的例子中，我们将使用URL扩展名来帮助确定媒体类型。此外，我们还设置默认介质类型TEXT_HTML在没有文件扩展名或当文件类型是未知时，这意味着JSP视图解析器将被用于在没有[known]%uA0URL扩展中。

下面是 pizza.jsp 默认使用JSP视图解析器内容

<%@ page language="java" contentType="text/html charset=utf-8"  pageEncoding="utf-8"%>
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
	<meta http-equiv="Content-Type" content="text/html charset=utf-8">
	<title>Pizza JSP View</title>
</head>
<body>
	<table border="1">
		<tr>
		<td>NAME</td>
		<td>Flavor</td>
		<td>Toppings</td>
		</tr>
		<tr>
			<td>${pizza.name}</td>
			<td>${pizza.flavor}</td>
			<td>
				<c:forEach var="item" items="${pizza.toppings}">
					<c:out value="${item}"/>&nbsp 
				</c:forEach>
			</td>
		</tr>
	</table>
</body>
</html>

下一步是配置 ContentNegotaionViewResolver 本身，

	public ViewResolver contentNegotiatingViewResolver(ContentNegotiationManager manager) {
		ContentNegotiatingViewResolver resolver = new ContentNegotiatingViewResolver()
		resolver.setContentNegotiationManager(manager)

		// Define all possible view resolvers
		List<ViewResolver> resolvers = new ArrayList<ViewResolver>()

		resolvers.add(jaxb2MarshallingXmlViewResolver())
		resolvers.add(jsonViewResolver())
		resolvers.add(jspViewResolver())
		resolvers.add(pdfViewResolver())
		resolvers.add(excelViewResolver())
		
		resolver.setViewResolvers(resolvers)
		return resolver
	}

我们需要设置 ContentNegotiationManager由Spring 注入，和为每一个应用程序可能会产生输出格式设置不同的解析器，。

最后，我们已经创建了不同的视图解析器以对 XML，JSON，PDF，XLS 和 HTML 输出，我们将在节中讨论。

第4步：创建不同的视图解析器

现在，让我们创建塔实际视图解析器

XML View Resolver:

这个视图解析器依赖于JAXB2编组/解组产生XML输出。domain类需要和JAXB2注释进行注释。

com.yiibai.springmvc.viewresolver.Jaxb2MarshallingXmlViewResolver

package com.yiiibai.springmvc.viewresolver

import java.util.Locale

import org.springframework.oxm.Marshaller
import org.springframework.web.servlet.View
import org.springframework.web.servlet.ViewResolver
import org.springframework.web.servlet.view.xml.MarshallingView

public class Jaxb2MarshallingXmlViewResolver implements ViewResolver {

	private Marshaller marshaller

    
    public Jaxb2MarshallingXmlViewResolver(Marshaller marshaller) {
        this.marshaller = marshaller
    }
    
    
    @Override
    public View resolveViewName(String viewName, Locale locale) throws Exception {
        MarshallingView view = new MarshallingView()
        view.setMarshaller(marshaller)
        return view
    }

}

下面是域对象(标注了标准的XML注释)在我们的例子：

com.yiibai.springmvc.model.Pizza

package com.yiibai.springmvc.model

import java.util.ArrayList
import java.util.List

import javax.xml.bind.annotation.XmlElement
import javax.xml.bind.annotation.XmlRootElement

@XmlRootElement(name = "pizza")
public class Pizza {
	
	private String name
	
	private String flavor
	
	private List<String> toppings = new ArrayList<String>()
	
	public Pizza(){
		
	}
	
	public Pizza(String name){
		this.name = name
		this.flavor = "spicy"
		this.toppings.add("Cheese")
		this.toppings.add("bakon")
	}
	
	@XmlElement
	public void setName(String name) {
		this.name = name
	}

	public String getName() {
		return name
	}

	@XmlElement
	public void setFlavor(String flavor) {
		this.flavor = flavor
	}

	public String getFlavor() {
		return flavor
	}

	public List<String> getToppings() {
		return toppings
	}
	
	@XmlElement
	public void setToppings(List<String> toppings) {
		this.toppings = toppings
	}
	
}

JSON View Resolver:

这个视图解析器是使用 Spring%uA0MappingJackson2JsonView 为了将 POJO 对象转换成 JSON 视图。

com.yiibai.springmvc.viewresolver.JsonViewResolver

package com.yiibai.springmvc.viewresolver

import java.util.Locale

import org.springframework.web.servlet.View
import org.springframework.web.servlet.ViewResolver
import org.springframework.web.servlet.view.json.MappingJackson2JsonView

public class JsonViewResolver implements ViewResolver{

	@Override
	public View resolveViewName(String viewName, Locale locale) throws Exception {
		MappingJackson2JsonView view = new MappingJackson2JsonView()
        view.setPrettyPrint(true)       
        return view
      }

}

PDF View Resolver:

这个视图解析器使用lowagie%uA0iText库实际生成PDF输出。还要注意的是实际的视图，从SpringꂫstractPdfView%uA0内部使用%uA0lowagie%uA0iText%uA0库扩展。

com.yiibai.springmvc.viewresolver.PdfView

package com.yiibai.springmvc.viewresolver

import java.awt.Color
import java.util.Map

import javax.servlet.http.HttpServletRequest
import javax.servlet.http.HttpServletResponse

import org.springframework.web.servlet.view.document.AbstractPdfView

import com.lowagie.text.Document
import com.lowagie.text.Element
import com.lowagie.text.pdf.PdfPTable
import com.lowagie.text.pdf.PdfWriter
import com.yiibai.springmvc.model.Pizza

public class PdfView extends AbstractPdfView {

	@Override
	protected void buildPdfDocument(Map<String, Object> model,
			Document document, PdfWriter writer, HttpServletRequest request,
			HttpServletResponse response) throws Exception {

		Pizza pizza = (Pizza) model.get("pizza")

		PdfPTable table = new PdfPTable(3)
		table.getDefaultCell().setHorizontalAlignment(Element.ALIGN_CENTER)
		table.getDefaultCell().setVerticalAlignment(Element.ALIGN_MIDDLE)
		table.getDefaultCell().setBackgroundColor(Color.lightGray)

		table.addCell("Name")
		table.addCell("Flavor")
		table.addCell("Toppings")

		table.addCell(pizza.getName())
		table.addCell(pizza.getFlavor())

		StringBuffer toppings = new StringBuffer("")
		for (String topping : pizza.getToppings()) {
			toppings.append(topping)
			toppings.append(" ")
		}
		table.addCell(toppings.toString())
		document.add(table)

	}

}

com.yiibai.springmvc.viewresolver.PdfViewResolver类代码：

package com.yiibai.springmvc.viewresolver

import java.util.Locale

import org.springframework.web.servlet.View
import org.springframework.web.servlet.ViewResolver

public class PdfViewResolver implements ViewResolver{

	@Override
	public View resolveViewName(String viewName, Locale locale) throws Exception {
		PdfView view = new PdfView()
		return view
      }
	
}

XLS View Resolver:

这个视图解析器是使用Apache%uA0POI库实际生成%uA0Microsoft%uA0XLS输出。还要注意的是实际的视图，从SpringꂫstractExcelView%uA0内部使用%uA0Apache%uA0POI库扩展。

com.yiibai.springmvc.viewresolver.ExcelView

package com.yiibai.springmvc.viewresolver

import java.util.Map

import javax.servlet.http.HttpServletRequest
import javax.servlet.http.HttpServletResponse

import org.apache.poi.hssf.usermodel.HSSFWorkbook
import org.apache.poi.ss.usermodel.Cell
import org.apache.poi.ss.usermodel.CellStyle
import org.apache.poi.ss.usermodel.IndexedColors
import org.apache.poi.ss.usermodel.Row
import org.apache.poi.ss.usermodel.Sheet
import org.springframework.web.servlet.view.document.AbstractExcelView

import com.yiibai.springmvc.model.Pizza

public class ExcelView extends AbstractExcelView {

	@Override
	protected void buildExcelDocument(Map<String, Object> model,
			HSSFWorkbook workbook, HttpServletRequest request,
			HttpServletResponse response) throws Exception {

		Pizza pizza = (Pizza) model.get("pizza")

		Sheet sheet = workbook.createSheet("sheet 1")
		CellStyle style = workbook.createCellStyle()
		style.setFillForegroundColor(IndexedColors.GREY_40_PERCENT.index)
		style.setFillPattern(CellStyle.SOLID_FOREGROUND)
		style.setAlignment(CellStyle.ALIGN_CENTER)
		Row row = null
		Cell cell = null
		int rowCount = 0
		int colCount = 0

		// Create header cells
		row = sheet.createRow(rowCount++)

		cell = row.createCell(colCount++)
		cell.setCellStyle(style)
		cell.setCellValue("Name")

		cell = row.createCell(colCount++)
		cell.setCellStyle(style)
		cell.setCellValue("Flavor")

		cell = row.createCell(colCount++)
		cell.setCellStyle(style)
		cell.setCellValue("Toppings")

		// Create data cells
		row = sheet.createRow(rowCount++)
		colCount = 0
		row.createCell(colCount++).setCellValue(pizza.getName())
		row.createCell(colCount++).setCellValue(pizza.getFlavor())

		StringBuffer toppings = new StringBuffer("")
		for (String topping : pizza.getToppings()) {
			toppings.append(topping)
			toppings.append(" ")
		}
		row.createCell(colCount++).setCellValue(toppings.toString())

		for (int i = 0 i < 3 i++)
			sheet.autoSizeColumn(i, true)

	}

}

com.yiibai.springmvc.viewresolver.ExcelViewResolver

package com.yiibai.springmvc.viewresolver

import java.util.Locale

import org.springframework.web.servlet.View
import org.springframework.web.servlet.ViewResolver

public class ExcelViewResolver implements ViewResolver{

	@Override
	public View resolveViewName(String viewName, Locale locale) throws Exception {
		ExcelView view = new ExcelView()
		return view
      }
	
}

这是所有 ContentNegotaingViewResolver%uA0需要的配置。

完成这个例子并让它可以运行，让我们添加缺少 Spring%uA0MVC 配置。

第5步：创建控制器类

下面是一个简单的基于REST的控制器作为我们的示例。

com.yiibai.springmvc.controller.AppController

package com.yiibai.springmvc.controller

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

import com.yiibai.springmvc.model.Pizza

@Controller
public class AppController {

	@RequestMapping(value="/pizzavalley/{pizzaName}", method = RequestMethod.GET)
	public String getPizza(@PathVariable String pizzaName, ModelMap model) {
 
		Pizza pizza = new Pizza(pizzaName)
		model.addAttribute("pizza", pizza)
 
		return "pizza"
 
	}
	
}

第6步：创建初始化类

添加一个初始化类实现WebApplicationInitializer如下图所示(在这种情况下，作为替代在%uA0web.xml%uA0中定义的任何 Spring%uA0配置)。在Servlet%uA03.0的容器启动时，这个类会被加载并实例及其 onStartup方法将通过servlet容器调用。

com.yiibai.springmvc.configuration.AppInitializer

package com.yiibai.springmvc.configuration

import javax.servlet.ServletContext
import javax.servlet.ServletException
import javax.servlet.ServletRegistration

import org.springframework.web.WebApplicationInitializer
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext
import org.springframework.web.servlet.DispatcherServlet

public class AppInitializer implements WebApplicationInitializer {

	public void onStartup(ServletContext container) throws ServletException {

		AnnotationConfigWebApplicationContext ctx = new AnnotationConfigWebApplicationContext()
		ctx.register(AppConfig.class)
		ctx.setServletContext(container)

		ServletRegistration.Dynamic servlet = container.addServlet(
				"dispatcher", new DispatcherServlet(ctx))

		servlet.setLoadOnStartup(1)
		servlet.addMapping("/")
	}

}
%uA0

更新：请注意，上面的类可以写成更加简洁[和它的首选方式]，通过扩展ꂫstractAnnotationConfigDispatcherServletInitializer%uA0基类，如下所示：

package com.yiibai.springmvc.configuration

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer

public class AppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

	@Override
	protected Class<?>[] getRootConfigClasses() {
		return new Class[] { AppConfig.class }
	}
 
	@Override
	protected Class<?>[] getServletConfigClasses() {
		return null
	}
 
	@Override
	protected String[] getServletMappings() {
		return new String[] { "/" }
	}

}