整合Servlet到Spring容器

有时在Spring(3.2.5)项目中，如果使用到Servlet，可能希望Servlet实例作为bean受Spring容器管理，这样也能自动注入其他需要的bean，查了下，发现只针对过滤器提供了代理类org.springframework.web.filter.DelegatingFilterProxy，并没有提供针对Servlet的代理类，于是模仿着写了下面的代理类:
??
package org.springframework.web.servlet;
?
import java.io.IOException;
import javax.servlet.Servlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.util.Assert;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.context.support.WebApplicationContextUtils;
?
?
/**
?*? Servlet代理类，将Servlet托管于Spring容器，以便直接在Servlet内部自动注入其他bean<br>
?*? 参考 {@code org.springframework.web.filter.DelegatingFilterProxy}<br>
?*/
@SuppressWarnings("serial")
public class DelegatingServletProxy extends HttpServletBean {
?
?private String contextAttribute;
?private WebApplicationContext webApplicationContext;
?private String targetBeanName;
?private boolean targetServletLifecycle = true;
?private volatile Servlet delegate;
?private final Object delegateMonitor = new Object();
?
?public DelegatingServletProxy() {
?}
?
?public DelegatingServletProxy(Servlet delegate) {
? Assert.notNull(delegate, "delegate Servlet object must not be null");
? this.delegate = delegate;
?}
?
?public DelegatingServletProxy(String targetBeanName) {
? this(targetBeanName, null);
?}
?
?public DelegatingServletProxy(String targetBeanName, WebApplicationContext wac) {
? Assert.hasText(targetBeanName, "target Servlet bean name must not be null or empty");
? this.setTargetBeanName(targetBeanName);
? this.webApplicationContext = wac;
? if (wac != null) {
?? this.setEnvironment(wac.getEnvironment());
? }
?}
?
?public void setContextAttribute(String contextAttribute) {
? this.contextAttribute = contextAttribute;
?}
?
?public String getContextAttribute() {
? return this.contextAttribute;
?}
?
?public void setTargetBeanName(String targetBeanName) {
? this.targetBeanName = targetBeanName;
?}
?
?protected String getTargetBeanName() {
? return this.targetBeanName;
?}
?
?public void setTargetServletLifecycle(boolean targetServletLifecycle) {
? this.targetServletLifecycle = targetServletLifecycle;
?}
?
?protected boolean isTargetServletLifecycle() {
? return this.targetServletLifecycle;
?}
?
?@Override
?protected void initServletBean() throws ServletException {
? synchronized (this.delegateMonitor) {
?? if (this.delegate == null) {
??? if (this.targetBeanName == null) {
???? this.targetBeanName = this.getServletName();
??? }
??? WebApplicationContext wac = this.findWebApplicationContext();
??? if (wac != null) {
???? this.delegate = this.initDelegate(wac);
??? }
?? }
? }
?}
?
?@Override
?public void service(ServletRequest req, ServletResponse resp) throws ServletException, IOException {
? Servlet delegateToUse = this.delegate;
? if (delegateToUse == null) {
?? synchronized (this.delegateMonitor) {
??? if (this.delegate == null) {
???? WebApplicationContext wac = this.findWebApplicationContext();
???? if (wac == null) {
????? throw new IllegalStateException("No WebApplicationContext found: no ContextLoaderListener registered?");
???? }
???? this.delegate = this.initDelegate(wac);
??? }
??? delegateToUse = this.delegate;
?? }
? }
? this.invokeDelegate(delegateToUse, req, resp);
?}
?
?@Override
?public void destroy() {
? Servlet delegateToUse = this.delegate;
? if (delegateToUse != null) {
?? this.destroyDelegate(delegateToUse);
? }
?}
?
?protected WebApplicationContext findWebApplicationContext() {
? if (this.webApplicationContext != null) {
?? if (this.webApplicationContext instanceof ConfigurableApplicationContext) {
??? if (!((ConfigurableApplicationContext) this.webApplicationContext).isActive()) {
???? ((ConfigurableApplicationContext) this.webApplicationContext).refresh();
??? }
?? }
?? return this.webApplicationContext;
? }
? String attrName = this.getContextAttribute();
? if (attrName != null) {
?? return WebApplicationContextUtils.getWebApplicationContext(super.getServletContext(), attrName);
? }
? else {
?? return WebApplicationContextUtils.getWebApplicationContext(super.getServletContext());
? }
?}
?
?protected Servlet initDelegate(WebApplicationContext wac) throws ServletException {
? Servlet delegate = wac.getBean(this.getTargetBeanName(), Servlet.class);
? if (this.isTargetServletLifecycle()) {
?? delegate.init(super.getServletConfig());
? }
? return delegate;
?}
?
?protected void invokeDelegate(Servlet delegate, ServletRequest req, ServletResponse resp) throws ServletException, IOException {
? delegate.service(req, resp);
?}
?
?protected void destroyDelegate(Servlet delegate) {
? if (this.isTargetServletLifecycle()) {
?? delegate.destroy();
? }
?}
?
}
?
//======================================================//
用法：
1、比如存在test.TestServlet，配置到spring对应xml中：
?<bean id="testServlet" class="test.TestServlet" />
?
2、在web.xml配置如下：
<servlet>
? <servlet-name>testServlet</servlet-name>
? <servlet-class>org.springframework.web.servlet.DelegatingServletProxy</servlet-class>
? <init-param>
?? <param-name>targetBeanName</param-name>
?? <param-value>testServlet</param-value>
? </init-param>
? <load-on-startup>10</load-on-startup>
?</servlet>
?
然后在TestServlet中可自动注入需要的bean。

整合Servlet到Spring容器

原文：http://long4063167370.iteye.com/blog/2150842