純代碼配置 SSM 框架 (二)

純代碼配置 SSM 框架 (二)

入口說明

Web 應用最重要的配置文件就是 web.xml 配置，它是 web 項目啓動時首先被容器讀取的配置文件,根據其中的配置創建實例並完成參數初始化等以保證項目能夠正確啓動運行。在 Spring MVC 框架中，只要實現 WebApplicationInitializer 接口，並重寫 void onStartup(ServletContext servletContext) throws ServletException; 方法，即可讓 Servlet 3.0 容器自動引導。

下面是 WebApplicationInitializer 接口的源碼，非常簡單。

package org.springframework.web;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;

public interface WebApplicationInitializer {
    void onStartup(ServletContext var1) throws ServletException;
}

官方的接口說明如下

Interface to be implemented in Servlet 3.0+ environments in order to configure the ServletContext programmatically – as opposed to (or possibly in conjunction with) the traditional web.xml-based approach.

這個 SPI 的實現將被 SpringServletContainerInitializer 自動檢測到，它本身是由任何 Servlet 3.0 容器自動引導的。

Implementations of this SPI will be detected automatically by SpringServletContainerInitializer, which itself is bootstrapped automatically by any Servlet 3.0 container.

實現該接口可以在 Servlet 3.0 + 環境中以編程方式配  ServletContext ，而不是(或結合)傳統的基於 web.xml 文件配置。

配置

web.xml 中配置的項目主要有:上下文參數、監聽器、過濾器。因爲純代碼配置，上下文參數會直接在代碼中配置中配置、過濾器將由DispatcherServlet配置，因此在該配置中，主要配置相關的監聽器。

WebInitializer配置如下:

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.core.annotation.Order;
import org.springframework.web.WebApplicationInitializer;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;

@Order(1)
public class WebInitializer implements WebApplicationInitializer {
    private static final Logger logger = LoggerFactory.getLogger(WebInitializer.class);

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        logger.info("onStartup");
        Log4j2Config.config(servletContext);
        SpringConfig.config(servletContext);
        DruidConfig.config(servletContext);
    }
}

@Order(1) : 通過該註解、規定了 Spring 加載順序。

因爲項目使用了 Druid 數據緩衝池、 2.x版本Log4j 日誌框架、和 Spring 相關監聽器。

Log4j2Config 配置如下:

import javax.servlet.ServletContext;
import java.util.EnumSet;

import static javax.servlet.DispatcherType.*;

public final class Log4j2Config {
    public static void config(ServletContext servletContext) {
        servletContext.setInitParameter("isLog4jAutoInitializationDisabled", "true");
        servletContext.getFilterRegistration("log4jServletFilter")
                .addMappingForUrlPatterns(
                        EnumSet.of(REQUEST, FORWARD, INCLUDE, ERROR, ASYNC),
                        false,
                        "/*");
    }
}

SpringConfig 配置如下:

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.web.context.request.RequestContextListener;
import org.springframework.web.filter.CharacterEncodingFilter;
import org.springframework.web.util.IntrospectorCleanupListener;

import javax.servlet.DispatcherType;
import javax.servlet.FilterRegistration;
import javax.servlet.ServletContext;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.Map;

public final class SpringConfig {
    private static final Logger logger = LoggerFactory.getLogger(SpringConfig.class);

    private static final String ENCODING_FILTER = "encodingFilter";

    public static void config(ServletContext servletContext) {
        logger.debug("RequestContextListener:request作用域");
        servletContext.addListener(RequestContextListener.class);
        logger.debug("IntrospectorCleanupListener:主要負責處理由JavaBeansIntrospector的使用而引起的緩衝泄露");
        servletContext.addListener(IntrospectorCleanupListener.class);
        logger.info("Spring字符集過濾器");
        FilterRegistration.Dynamic dynamic = servletContext.addFilter(ENCODING_FILTER, CharacterEncodingFilter.class);
        Map<String, String> map = new HashMap<>();
        map.put("encoding", "UTF-8");
        map.put("forceEncoding", "true");
        dynamic.setInitParameters(map);
        dynamic.addMappingForUrlPatterns(EnumSet.of(
                DispatcherType.REQUEST,
                DispatcherType.FORWARD,
                DispatcherType.INCLUDE,
                DispatcherType.ERROR,
                DispatcherType.ASYNC),
                false,
                "/*");
    }
}

DruidConfig 配置如下:

import com.alibaba.druid.support.http.StatViewServlet;
import com.alibaba.druid.support.http.WebStatFilter;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import javax.servlet.DispatcherType;
import javax.servlet.FilterRegistration;
import javax.servlet.ServletContext;
import javax.servlet.ServletRegistration;
import java.util.EnumSet;
import java.util.HashMap;
import java.util.Map;

public final class DruidConfig {
    private static final Logger logger = LoggerFactory.getLogger(DruidConfig.class);

    private static final String DRUID_WEB_STAT_FILTER = "DruidWebStatFilter";
    private static final String DRUID_STAT_VIEW_SERVLET = "DruidStatViewServlet";

    public static void config(ServletContext servletContext) {
        logger.info("配置阿里雲監控");
        configDruidWebStatFilter(servletContext);
        configDruidStatView(servletContext);
    }

    private static void configDruidStatView(ServletContext servletContext) {
        logger.info("配置druid頁面顯示");
        ServletRegistration.Dynamic dynamic = servletContext.addServlet(DRUID_STAT_VIEW_SERVLET, StatViewServlet.class);
        Map<String, String> map = new HashMap<>();
        map.put("profileEnable", "true");
        map.put("resetEnable", "true");
        map.put("loginUsername", "賬號");
        map.put("loginPassword", "密碼");
        dynamic.setInitParameters(map);
        dynamic.addMapping("/druid/*");
    }

    private static void configDruidWebStatFilter(ServletContext servletContext) {
        logger.info("阿里數據源,連接池啓用Web監控統計功能START");
        FilterRegistration.Dynamic dynamic = servletContext.addFilter(DRUID_WEB_STAT_FILTER, WebStatFilter.class);
        Map<String, String> map = new HashMap<>();
        map.put("exclusions", "*.js,*.gif,*.jpg,*.png,*.css,*.ico,/druid/*");
        dynamic.setInitParameters(map);
        dynamic.addMappingForUrlPatterns(EnumSet.of(
                DispatcherType.REQUEST,
                DispatcherType.FORWARD,
                DispatcherType.INCLUDE,
                DispatcherType.ERROR,
                DispatcherType.ASYNC),
                false,
                "/*");
    }
}