{"id":53297,"date":"2016-03-02T10:00:23","date_gmt":"2016-03-02T08:00:23","guid":{"rendered":"http:\/\/www.javacodegeeks.com\/?p=53297"},"modified":"2016-03-01T10:23:16","modified_gmt":"2016-03-01T08:23:16","slug":"configure-multiple-view-resolvers-spring","status":"publish","type":"post","link":"https:\/\/www.javacodegeeks.com\/2016\/03\/configure-multiple-view-resolvers-spring.html","title":{"rendered":"Configure multiple View Resolvers in Spring"},"content":{"rendered":"

1. Introduction<\/h2>\n

In Spring, the View Resolver is provided to resolve the view with the data available in the model, without tightly binding to a\u00a0View technology, be it JSP, Velocity or Thymeleaf. Spring makes it easy and flexible to configure one or multiple\u00a0View Resolvers<\/strong>, as\u00a0per the need would be.<\/p>\n

2. Spring MVC application flow<\/h2>\n

Before we proceed with understanding how multiple View Resolvers<\/strong>\u00a0serve the purpose, lets take a quick recap of the Spring MVC application flow<\/a>.<\/p>\n

    \n
  1. Incoming request comes through web.xml<\/strong>, dispatcher servlet<\/strong> and hits the controller<\/strong>.<\/li>\n
  2. Controller interacts with the application layers and prepares the model<\/strong>.<\/li>\n
  3. Controller returns the ModelAndView<\/strong>, with model and the view name.<\/li>\n
  4. The ViewResolver<\/strong> provides a mapping between view names and actual views.<\/li>\n
  5. The View<\/strong> interface addresses the request of a view to respective View technology.<\/li>\n
  6. The view is then rendered onto the browser along with the model data.<\/li>\n<\/ol>\n

    3. Implementation<\/h2>\n

    Let\u2019s start with the pom dependencies.<\/p>\n

    pom.xml<\/em><\/strong><\/p>\n

    <!-- Spring 3 dependencies -->\r\n<dependency>\r\n\t<groupId>org.springframework<\/groupId>\r\n\t<artifactId>spring-core<\/artifactId>\r\n\t<version>${spring.version}<\/version>\r\n<\/dependency>\r\n \r\n<dependency>\r\n\t<groupId>org.springframework<\/groupId>\r\n\t<artifactId>spring-web<\/artifactId>\r\n\t<version>${spring.version}<\/version>\r\n<\/dependency>\r\n \r\n<dependency>\r\n\t<groupId>org.springframework<\/groupId>\r\n\t<artifactId>spring-webmvc<\/artifactId>\r\n\t<version>${spring.version}<\/version>\r\n<\/dependency>\r\n \r\n<!-- Jackson JSON Mapper -->\r\n<dependency>\r\n\t<groupId>org.codehaus.jackson<\/groupId>\r\n\t<artifactId>jackson-mapper-asl<\/artifactId>\r\n\t<version>${jackson.version}<\/version>\r\n<\/dependency>\r\n \r\n<!-- JSTL Dependency -->\r\n<dependency>\r\n\t<groupId>jstl<\/groupId>\r\n\t<artifactId>jstl<\/artifactId>\r\n\t<version>${jstl.version}<\/version>\r\n<\/dependency><\/pre>\n
    Not much change in the web.xml.<\/p>\n
    web.xml<\/em><\/strong><\/p>\n
    <?xml version=\"1.0\" encoding=\"ISO-8859-1\"?>\r\n<web-app xmlns:xsi=\"http:\/\/www.w3.org\/2001\/XMLSchema-instance\"\r\n\txmlns=\"http:\/\/java.sun.com\/xml\/ns\/javaee\"\r\n\txsi:schemaLocation=\"http:\/\/java.sun.com\/xml\/ns\/javaee\r\n\thttp:\/\/java.sun.com\/xml\/ns\/javaee\/web-app_2_5.xsd\"\r\n\tid=\"WebApp_ID\" version=\"2.5\">\r\n \r\n\t<display-name>MultipleViewResolversExample<\/display-name>\r\n \r\n\t<servlet>\r\n\t\t<servlet-name>mvc-dispatcher<\/servlet-name>\r\n\t\t<servlet-class>org.springframework.web.servlet.DispatcherServlet<\/servlet-class>\r\n\t\t<load-on-startup>1<\/load-on-startup>\r\n\t<\/servlet>\r\n \r\n\t<servlet-mapping>\r\n\t\t<servlet-name>mvc-dispatcher<\/servlet-name>\r\n\t\t<url-pattern>\/API\/*<\/url-pattern>\r\n\t<\/servlet-mapping>\r\n \r\n<\/web-app><\/pre>\n
    Here is the mvc-dispatcher-servlet, which has multiple View Resolvers defined<\/strong>.
     
    <\/div> <\/div><\/p>\n
    mvc-dispatcher-servlet.xml<\/em><\/strong><\/p>\n
    <beans xmlns=\"http:\/\/www.springframework.org\/schema\/beans\"\r\n\txmlns:context=\"http:\/\/www.springframework.org\/schema\/context\"\r\n\txmlns:mvc=\"http:\/\/www.springframework.org\/schema\/mvc\" xmlns:xsi=\"http:\/\/www.w3.org\/2001\/XMLSchema-instance\"\r\n\txsi:schemaLocation=\"http:\/\/www.springframework.org\/schema\/mvc http:\/\/www.springframework.org\/schema\/mvc\/spring-mvc.xsd\r\n\thttp:\/\/www.springframework.org\/schema\/beans http:\/\/www.springframework.org\/schema\/beans\/spring-beans-3.0.xsd http:\/\/www.springframework.org\/schema\/context \r\n        http:\/\/www.springframework.org\/schema\/context\/spring-context-3.0.xsd http:\/\/www.springframework.org\/schema\/mvc http:\/\/www.springframework.org\/schema\/mvc\/spring-mvc-3.0.xsd\">\r\n \r\n\t<mvc:annotation-driven \/>\r\n\t<context:component-scan base-package=\"com.jcombat.controller\" \/>\r\n \r\n\t<!-- Bean View Resolver -->\r\n\t<bean class=\"org.springframework.web.servlet.view.BeanNameViewResolver\">\r\n\t\t<property name=\"order\" value=\"0\" \/>\r\n\t<\/bean>\r\n \r\n\t<!-- JSP View Resolver -->\r\n\t<bean\r\n\t\tclass=\"org.springframework.web.servlet.view.InternalResourceViewResolver\">\r\n\t\t<property name=\"prefix\">\r\n\t\t\t<value>\/WEB-INF\/<\/value>\r\n\t\t<\/property>\r\n\t\t<property name=\"suffix\">\r\n\t\t\t<value>.jsp<\/value>\r\n\t\t<\/property>\r\n\t\t<property name=\"order\" value=\"1\" \/>\r\n\t<\/bean>\r\n \r\n\t<bean name=\"jsonView\"\r\n\t\tclass=\"org.springframework.web.servlet.view.json.MappingJacksonJsonView\" \/>\r\n \r\n<\/beans><\/pre>\n
    Note that the two View Resolvers configured are InternalResourceViewResolver<\/strong> and\u00a0BeanNameViewResolver<\/a><\/strong>. We have\u00a0also set the priorities using the order<\/strong> property of the View Resolver. So\u00a0BeanNameViewResolver\u00a0<\/strong>has a higher priority. This means that when the ModelAndView<\/strong> object is returned, the\u00a0BeanNameViewResolver <\/strong>checks for the available bean views with the view name that is returned. If the matching bean view is found, it is rendered. If not, the next View Resolver i.e.\u00a0InternalResourceViewResolver<\/strong>, comes into the picture, and similarly\u00a0checks for the JSPs with the view name that is returned with\u00a0ModelAndView<\/strong>. If it is found, the view is rendered. But if not, and\u00a0there is no more View Resolvers down the hierarchy, an\u00a0appropriate exception is thrown.<\/p>\n
    Moving ahead with the implemetation, we have the same Employee entity class, as we have been using recently.<\/p>\n
    Employee.java<\/em><\/strong><\/p>\n
    package com.jcombat.bean;\r\n \r\npublic class Employee {\r\n\tprivate String empId;\r\n\tprivate String name;\r\n\t\r\n\tpublic String getEmpId() {\r\n\t\treturn empId;\r\n\t}\r\n\tpublic void setEmpId(String empId) {\r\n\t\tthis.empId = empId;\r\n\t}\r\n\tpublic String getName() {\r\n\t\treturn name;\r\n\t}\r\n\tpublic void setName(String name) {\r\n\t\tthis.name = name;\r\n\t}\r\n}<\/pre>\n
    Let\u2019s now write down the EmployeeController<\/strong>.<\/p>\n
    EmployeeController.java<\/em><\/p>\n
    package com.jcombat.controller;\r\n \r\nimport org.springframework.stereotype.Controller;\r\nimport org.springframework.web.bind.annotation.PathVariable;\r\nimport org.springframework.web.bind.annotation.RequestMapping;\r\nimport org.springframework.web.bind.annotation.RequestMethod;\r\nimport org.springframework.web.servlet.ModelAndView;\r\n \r\nimport com.jcombat.bean.Employee;\r\n \r\n@Controller\r\n@RequestMapping(value = \"\/Employee\")\r\npublic class EmployeeController {\r\n \r\n\t@RequestMapping(value = \"\/{name}\/{empId}\", method = RequestMethod.GET)\r\n\tpublic ModelAndView process(\r\n\t\t\t@PathVariable(\"name\") String name,\r\n\t\t\t@PathVariable(\"empId\") String empId) {\r\n\t\tModelAndView modelAndView = new ModelAndView();\r\n\t\tEmployee employee = new Employee();\r\n\t\temployee.setEmpId(empId);\r\n\t\temployee.setName(name);\r\n\t\tmodelAndView.setViewName(\"employeeDetails\");\r\n\t\tmodelAndView.addObject(\"employee\", employee);\r\n\t\treturn modelAndView;\r\n\t}\r\n}<\/pre>\n
    We now make sure the JSP with the view name \u2013 employeeDetails<\/strong>, exists.<\/p>\n
    employeeDetails.jsp<\/em><\/strong><\/p>\n
    <%@page contentType=\"text\/html\" pageEncoding=\"UTF-8\"%>\r\n<!DOCTYPE HTML PUBLIC \"-\/\/W3C\/\/DTD HTML 4.01 Transitional\/\/EN\"\r\n   \"http:\/\/www.w3.org\/TR\/html4\/loose.dtd\">\r\n<html>\r\n\t<head>\r\n\t\t<meta http-equiv=\"Content-Type\" content=\"text\/html; charset=ISO-8859-1\">\r\n\t\t<title>Via JSP View Resolver<\/title>\r\n\t<\/head>\r\n\t<body>\r\n\t\t<!-- Retrieve the model data through JSTL -->\r\n\t\t<p>${employee.empId}<\/p>\r\n\t\t<p>${employee.name}<\/p>\r\n\t<\/body>\r\n<\/html><\/pre>\n
    4. Running the application<\/h2>\n
    When we\u00a0run the application, below is what we see.<\/p>\n
    \"Snap1\"<\/a><\/p>\n
    Note that we don\u2019t have any bean view with name employeeDetails<\/strong>,\u00a0but rather matches\u00a0with the actual JSP view file employeeDetails.jsp<\/strong>. Hence, the view gets resolved as JSP.<\/p>\n
    Now let\u2019s return the view name as jsonView<\/strong>, modifying the below statement in the controller method.<\/p>\n
    modelAndView.setViewName(\"jsonView\");<\/pre>\n
    BeanNameViewResolver<\/strong> being higher in priority, this time finds the bean view with the name jsonView<\/strong>, and instead of rendering the JSP view, the same URI now returns a JSON<\/strong>.<\/p>\n
    \"Snap2\"<\/a><\/p>\n
    5. Download the source code<\/h2>\n