今天要分享用Java Config初始化Java Web應用程式，不需要再撰寫web.xml檔，這項feature是自Servlet 3.0以後才支援，也意味著Tomcat 7以後才能跑，Springframwork提供一開始提供一個介面WebApplicationInitializer提供實作DispatchServlet，後來提供實作WebApplicationInitializer​兩個抽象類別 AbstractDispatcherServletInitializer( for載入Spring組態設定檔, 如)application context.xml以及AbstractAnnotationConfigDispatcherServletInitializer( for 載入Java Config Class)，其實差別僅在於前者必須透過XmlWebApplicationContext載入xml組態檔，後者提供Java Config class檔，前者code如下，新增一個class WebConfigForWebApplicationContext並繼承AbstractDispatcherServletInitializer，

package tw.blogger.springtech.springmvc.config;

import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.XmlWebApplicationContext;
import org.springframework.web.servlet.support.AbstractDispatcherServletInitializer;

public class WebConfigForWebApplicationContext extends
		AbstractDispatcherServletInitializer {

	@Override
	protected WebApplicationContext createServletApplicationContext() {
		// TODO Auto-generated method stub
		XmlWebApplicationContext ctx=new XmlWebApplicationContext();
		ctx.setConfigLocation("/WEB-INF/springconfig/dispatchservletcontext.xml");
		return ctx;
	}

	@Override
	protected String[] getServletMappings() {
		// TODO Auto-generated method stub
//		return null;
		 return new String[] { "/" };
	}

	@Override
	protected WebApplicationContext createRootApplicationContext() {
		// TODO Auto-generated method stub
		//return null;
		XmlWebApplicationContext ctx=new XmlWebApplicationContext();
		ctx.setConfigLocation("/WEB-INF/springconfig/service.xml"); //如果有多個xml要載入的話，
													                //可以選擇setConfigLocations，以陣列型式傳入
		return ctx;
	}

}

另外service.xml改寫成ServiceConfig，boneCP的相關參數值用官方建議數值，然後新增jdbcTemplate bean以及拿掉MyDAO:

package tw.blogger.springtech.springmvc.config;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.core.env.Environment;
import org.springframework.jdbc.core.JdbcTemplate;

import com.jolbox.bonecp.BoneCPDataSource;


@PropertySource(value="classpath:jdbc.properties")
@Configuration
public class ServiceConfig {
	
	@Autowired
	Environment env; //Environment物件存放Profile以及Property Source
	
	@Bean
	public BoneCPDataSource datasource(){
		BoneCPDataSource datasource = new BoneCPDataSource();
		/*以下就設定一些dataSource的參數，url, username及password key/value pair
		 * 另外存在jdbc.properties檔裡，再用eng.getProperty("key")取得value，
		 */
        datasource.setDriverClass("com.mysql.jdbc.Driver");
        datasource.setJdbcUrl(env.getProperty("jdbc.url"));
        datasource.setUsername(env.getProperty("jdbc.username"));
        datasource.setPassword(env.getProperty("jdbc.password"));
        datasource.setIdleConnectionTestPeriodInMinutes(60);
        datasource.setIdleMaxAgeInMinutes(420);
        datasource.setMaxConnectionsPerPartition(30);
        datasource.setMinConnectionsPerPartition(10);
        datasource.setPartitionCount(3);
        datasource.setAcquireIncrement(5);
        datasource.setStatementsCacheSize(100);
       
 
        return datasource;
	}
	
	@Bean
	public JdbcTemplate jdbcTemplate(){
		return new JdbcTemplate(datasource()); //Dependency Injection只需要呼叫方法即可
	}
}

Java Config的code如下，新增一個class WebConfigForJavaConfig並繼承AbstractAnnotationDispatcherServletInitializer，:

package tw.blogger.springtech.springmvc.config;

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

public class WebConfigForJavaConfig extends
AbstractAnnotationConfigDispatcherServletInitializer {

@Override
protected Class<?>[] getRootConfigClasses() {
// TODO Auto-generated method stub
// return null;
return new Class<?> []{ServiceConfig.class}; //如同contextListener載入Service.xml或是其他helper
}

@Override
protected Class<?>[] getServletConfigClasses() {
// TODO Auto-generated method stub
//return null;
return new Class<?>[]{MVCConfig.class}; //傳回DispatchServlet Java Config Class
}

@Override
protected String[] getServletMappings() {
// TODO Auto-generated method stub
//return null;
return new String[] {"/"}; //相當於Servlet Mapping底下的<url-pattern>/</url-pattern>
}

}

Java Config以及XML載入只能選一個，否則Server無法正常啟動，因為兩個基本上都是註冊DispatchServlet，錯誤訊息如下。

資訊: Spring WebApplicationInitializers detected on classpath: [tw.blogger.springtech.springmvc.config.WebConfigForJavaConfig@4a1ed3fc, tw.blogger.springtech.springmvc.config.WebConfigForWebApplicationContext@6cfca244]
.......
Caused by: java.lang.IllegalArgumentException: Failed to register servlet with name 'dispatcher'.Check if there is another servlet registered under the same name.
......


如果拿掉一個，成功執行畫以及專案目錄截圖如下:

<img src="http://ithelp.ithome.com.tw/upload/images/20141005/2014100522522154315b258199d_resize_600.png" style="height:304px; width:600px"></img><img src="http://ithelp.ithome.com.tw/upload/images/20141005/2014100522523654315b340d5b9_resize_600.png" style="height:534px; width:427px"></img>

另外之前的專案都忘記放入log4j的設定檔，放置位置在src/main/resources，其xml code如下:

<?xml version="1.0" encoding="UTF-8"?>

<log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">

	<!-- Appenders -->
	<appender name="console" class="org.apache.log4j.ConsoleAppender">
		<param name="Target" value="System.out" />
		<layout class="org.apache.log4j.PatternLayout">
			<param name="ConversionPattern" value="%d{HH:mm:ss} [%t] %c{1} - %m%n" />
		</layout>
	</appender>
	
	<logger name="tw.blogger.springtech.springmvc.mvc">
		<level value="debug" />
	</logger>

	<logger name="org.springframework.http">
		<level value="debug" />
	</logger>

	<logger name="org.springframework.web">
		<level value="debug" />
	</logger>

	<root>
		<priority value="warn" />
		<appender-ref ref="console" />
	</root>
	
</log4j:configuration>

個人通常都看http、web及自己有興趣的部分，之後也可以再加。

今天就先到這裡，明天繼續囉