java Struts2和Freemarker整合應用靜態頁面

利用Struts2生成靜態頁面其實很靈活，很強大，尤其是利用Struts2對Freemarker較好的支持，充分利用Freemarker的模板功能來生成靜態 頁面。

基本思路為：利用Struts2對自定義result type的支持，自定義能夠生成靜態頁面的result type，結合模板引擎Freemarker可以實現大批量靜態頁面的生成。

參看org.apache.struts2.views.freemarker.FreemarkerResult的代碼實現，自定義了自己的生成靜態頁 面的result type。此種方案不單純用于生成靜態頁面，其實也可以用于生成諸如wml、xhtml等內容，具體可以參考Struts2缺省提供的各種result type的實現。

package com.mobilesoft.esales.webapp.action; 
import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.Writer;
import java.util.Locale; 
import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse; 
import org.apache.struts2.ServletActionContext;
import org.apache.struts2.dispatcher.StrutsResultSupport;
import org.apache.struts2.views.freemarker.FreemarkerManager;
import org.apache.struts2.views.util.ResourceUtil; 
import com.opensymphony.xwork2.ActionContext;
import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.LocaleProvider;
import com.opensymphony.xwork2.inject.Inject;
import com.opensymphony.xwork2.util.ValueStack; 
import freemarker.template.Configuration;
import freemarker.template.ObjectWrapper;
import freemarker.template.Template;
import freemarker.template.TemplateException;
import freemarker.template.TemplateModel;
import freemarker.template.TemplateModelException; 

public class FreemarkerResult extends StrutsResultSupport { 
    private static final long serialVersionUID = -3778230771704661631L; 
    protected ActionInvocation invocation;
    protected Configuration configuration;
    protected ObjectWrapper wrapper;
    protected FreemarkerManager freemarkerManager;
    private Writer writer;
    protected String location;
    private String pContentType = “text/html”; 
    protected String fileName; // 要生成的靜態頁面名稱
    protected String filePath; // 要生成的靜態頁面的路徑
    protected String staticTemplate; // 用于生成靜態頁面Freemarker模板的路徑 
    public FreemarkerResult() {
        super();
    } 
    public FreemarkerResult(String location) {
        super(location);
    } 
    @Inject
    public void setFreemarkerManager(FreemarkerManager mgr) {
        this.freemarkerManager = mgr;
    } 
    public void setContentType(String aContentType) {
        pContentType = aContentType;
    } 
    public String getContentType() {
        return pContentType;
    } 
    public void doExecute(String location, ActionInvocation invocation)
            throws IOException, TemplateException {
        this.location = location;
        this.invocation = invocation;
        this.configuration = getConfiguration();
        this.wrapper = getObjectWrapper(); 
        this.fileName = (String) conditionalParse(fileName, invocation);
        this.staticTemplate = (String) conditionalParse(staticTemplate, invocation);
        this.filePath = ((String) conditionalParse(filePath, invocation)) == null ? “”
                : ((String) conditionalParse(filePath, invocation)); 
        if (!location.startsWith(”/”)) {
            ActionContext ctx = invocation.getInvocationContext();
            HttpServletRequest req = (HttpServletRequest) ctx
                    .get(ServletActionContext.HTTP_REQUEST);
            String base = ResourceUtil.getResourceBase(req);
            location = base + “/” + location;
        } 
        //生成html頁面的模板類
        Template template = configuration.getTemplate(location, deduceLocale());
        // 生成靜態頁面的的模板類
        Template staticTemplate = configuration.getTemplate(this.staticTemplate,
                deduceLocale()); 
        TemplateModel model = createModel();
        String path = ServletActionContext.getServletContext().getRealPath(
                filePath)
                + File.separator;
        Writer out = new BufferedWriter(new OutputStreamWriter(
                new FileOutputStream(path + fileName))); 
        if (preTemplateProcess(template, model)) {
            try {
                staticTemplate.process(model, out);
                template.process(model, getWriter());
            } finally {
                postTemplateProcess(template, model);
                postTemplateProcess(staticTemplate, model);
            }
        }
    } 
    protected Configuration getConfiguration() throws TemplateException {
        return freemarkerManager.getConfiguration(ServletActionContext
                .getServletContext());
    } 
    protected ObjectWrapper getObjectWrapper() {
        return configuration.getObjectWrapper();
    } 
    public void setWriter(Writer writer) {
        this.writer = writer;
    } 
    protected Writer getWriter() throws IOException {
        if (writer != null) {
            return writer;
        }
        return ServletActionContext.getResponse().getWriter();
    } 
    protected TemplateModel createModel() throws TemplateModelException {
        ServletContext servletContext = ServletActionContext
                .getServletContext();
        HttpServletRequest request = ServletActionContext.getRequest();
        HttpServletResponse response = ServletActionContext.getResponse();
        ValueStack stack = ServletActionContext.getContext().getValueStack(); 
        Object action = null;
        if (invocation != null)
            action = invocation.getAction(); // Added for NullPointException
        return freemarkerManager.buildTemplateModel(stack, action,
                servletContext, request, response, wrapper);
    } 
    protected Locale deduceLocale() {
        if (invocation.getAction() instanceof LocaleProvider) {
            return ((LocaleProvider) invocation.getAction()).getLocale();
        } else {
            return configuration.getLocale();
        }
    } 
    protected void postTemplateProcess(Template template, TemplateModel data)
            throws IOException {
    } 
    protected boolean preTemplateProcess(Template template, TemplateModel model)
            throws IOException {
        Object attrContentType = template.getCustomAttribute(”content_type”); 
        if (attrContentType != null) {
            ServletActionContext.getResponse().setContentType(
                    attrContentType.toString());
        } else {
            String contentType = getContentType(); 
            if (contentType == null) {
                contentType = “text/html”;
            } 
            String encoding = template.getEncoding(); 
            if (encoding != null) {
                contentType = contentType + “; charset=” + encoding;
            } 
            ServletActionContext.getResponse().setContentType(contentType);
        } 
        return true;
    } 
    public String getFileName() {
        return fileName;
    } 
    public void setFileName(String fileName) {
        this.fileName = fileName;
    } 
    public String getFilePath() {
        return filePath;
    } 
    public void setFilePath(String filePath) {
        this.filePath = filePath;
    } 
    public String getStaticTemplate() {
        return staticTemplate;
    } 
    public void setStaticTemplate(String staticTemplate) {
        this.staticTemplate = staticTemplate;
    }
}