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Spring已集成jsp的环境下同时集成Velocity

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Spring集成Velocity时所需的扩展类

VelocityLayoutView.java

package com.my.velocity;

import java.io.StringWriter;
import java.util.Locale;

import javax.servlet.http.HttpServletResponse;

import org.apache.velocity.Template;
import org.apache.velocity.context.Context;
import org.apache.velocity.exception.ResourceNotFoundException;
import org.springframework.core.NestedIOException;
import org.springframework.web.servlet.view.velocity.VelocityToolboxView;

public class VelocityLayoutView extends VelocityToolboxView {
    /**
     * The default {@link #setLayoutUrl(String) layout url}.
     */
    public static final String DEFAULT_LAYOUT_URL = "layout.vm";
    public static final String DEFAULT_LAYOUT_DIR = "/";
    /**
     * The default {@link #setLayoutKey(String) layout key}.
     */
    public static final String DEFAULT_LAYOUT_KEY = "layout";

    /**
     * The default {@link #setScreenContentKey(String) screen content key}.
     */
    public static final String DEFAULT_SCREEN_CONTENT_KEY = "screen_content";

    private String layoutUrl = DEFAULT_LAYOUT_URL;

    private String layoutKey = DEFAULT_LAYOUT_KEY;
    private String screenContentKey = DEFAULT_SCREEN_CONTENT_KEY;
    private String layoutDir = DEFAULT_LAYOUT_DIR;

    /**
     * Set the layout template to use. Default is {@link #DEFAULT_LAYOUT_URL "layout.vm"}.
     * @param layoutUrl the template location (relative to the template
     * root directory)
     */
    public void setLayoutUrl(String layoutUrl) {
        this.layoutUrl = layoutUrl;
    }
    public String getLayoutDir() {
        return layoutDir;
    }

    public void setLayoutDir(String layoutDir) {
        this.layoutDir = layoutDir;
    }

    /**
     * Set the context key used to specify an alternate layout to be used instead
     * of the default layout. Screen content templates can override the layout
     * template that they wish to be wrapped with by setting this value in the
     * template, for example:<br>
     * <code>#set( $layout = "MyLayout.vm" )</code>
     * <p>Default key is {@link #DEFAULT_LAYOUT_KEY "layout"}, as illustrated above.
     * @param layoutKey the name of the key you wish to use in your
     * screen content templates to override the layout template
     */
    public void setLayoutKey(String layoutKey) {
        this.layoutKey = layoutKey;
    }

    /**
     * Set the name of the context key that will hold the content of
     * the screen within the layout template. This key must be present
     * in the layout template for the current screen to be rendered.
     * <p>Default is {@link #DEFAULT_SCREEN_CONTENT_KEY "screen_content"}:
     * accessed in VTL as <code>$screen_content</code>.
     * @param screenContentKey the name of the screen content key to use
     */
    public void setScreenContentKey(String screenContentKey) {
        this.screenContentKey = screenContentKey;
    }

    /**
     * Overrides <code>VelocityView.checkTemplate()</code> to additionally check
     * that both the layout template and the screen content template can be loaded.
     * Note that during rendering of the screen content, the layout template
     * can be changed which may invalidate any early checking done here.
     */
    @Override
    public boolean checkResource(Locale locale) throws Exception {
        if (!super.checkResource(locale)) {
            return false;
        }

        try {
            // Check that we can get the template, even if we might subsequently get it again.
            getTemplate(this.layoutUrl);
            return true;
        }
        catch (ResourceNotFoundException ex) {
            throw new NestedIOException("Cannot find Velocity template for URL [" + this.layoutUrl +
                    "]: Did you specify the correct resource loader path?", ex);
        }
        catch (Exception ex) {
            throw new NestedIOException(
                    "Could not load Velocity template for URL [" + this.layoutUrl + "]", ex);
        }
    }

    /**
     * Overrides the normal rendering process in order to pre-process the Context,
     * merging it with the screen template into a single value (identified by the
     * value of screenContentKey). The layout template is then merged with the
     * modified Context in the super class.
     */
    @Override
    protected void doRender(Context context, HttpServletResponse response) throws Exception {
        renderScreenContent(context);

        // Velocity context now includes any mappings that were defined
        // (via #set) in screen content template.
        // The screen template can overrule the layout by doing
        // #set( $layout = "MyLayout.vm" )
        String layoutUrlToUse = (String) context.get(this.layoutKey);
        if (layoutUrlToUse != null) {
            if (logger.isDebugEnabled()) {
                logger.debug("Screen content template has requested layout [" + layoutUrlToUse + "]");
            }
            if(this.layoutDir != null){
                layoutUrlToUse = this.layoutDir + layoutUrlToUse;
            }
        }
        else {
            // No explicit layout URL given -> use default layout of this view.
            layoutUrlToUse = this.layoutUrl;
        }

        mergeTemplate(getTemplate(layoutUrlToUse), context, response);
    }

    /**
     * The resulting context contains any mappings from render, plus screen content.
     */
    private void renderScreenContent(Context velocityContext) throws Exception {
        if (logger.isDebugEnabled()) {
            logger.debug("Rendering screen content template [" + getUrl() + "]");
        }

        StringWriter sw = new StringWriter();
        Template screenContentTemplate = getTemplate(getUrl());
        screenContentTemplate.merge(velocityContext, sw);

        // Put rendered content into Velocity context.
        velocityContext.put(this.screenContentKey, sw.toString());
    }
}

VelocityResolver.java

package com.my.velocity;

import org.springframework.web.servlet.view.AbstractUrlBasedView;
import org.springframework.web.servlet.view.velocity.VelocityViewResolver;

public class VelocityResolver extends VelocityViewResolver {

    private String layoutUrl;
    private String layoutKey;
    private String screenContentKey;
    private String layoutDir;

    public String getLayoutDir() {
        return layoutDir;
    }
    public void setLayoutDir(String layoutDir) {
        this.layoutDir = layoutDir;
    }
    /**
     * Set the layout template to use. Default is "layout.vm".
     * @param layoutUrl the template location (relative to the template
     * root directory)
     * @see VelocityLayoutView#setLayoutUrl
     */
    public void setLayoutUrl(String layoutUrl) {
        this.layoutUrl = layoutUrl;
    }

    /**
     * Set the context key used to specify an alternate layout to be used instead
     * of the default layout. Screen content templates can override the layout
     * template that they wish to be wrapped with by setting this value in the
     * template, for example:<br>
     * <code>#set( $layout = "MyLayout.vm" )</code>
     * <p>The default key is "layout", as illustrated above.
     * @param layoutKey the name of the key you wish to use in your
     * screen content templates to override the layout template
     * @see VelocityLayoutView#setLayoutKey
     */
    public void setLayoutKey(String layoutKey) {
        this.layoutKey = layoutKey;
    }

    /**
     * Set the name of the context key that will hold the content of
     * the screen within the layout template. This key must be present
     * in the layout template for the current screen to be rendered.
     * <p>Default is "screen_content": accessed in VTL as
     * <code>$screen_content</code>.
     * @param screenContentKey the name of the screen content key to use
     * @see VelocityLayoutView#setScreenContentKey
     */
    public void setScreenContentKey(String screenContentKey) {
        this.screenContentKey = screenContentKey;
    }

    /**
     * Requires VelocityLayoutView.
     * @see VelocityLayoutView
     */
    protected Class requiredViewClass() {
        return VelocityLayoutView.class;
    }

    protected AbstractUrlBasedView buildView(String viewName) throws Exception {
        VelocityLayoutView view = (VelocityLayoutView) super.buildView(viewName);
        //设置模版文件(layout)的根目录
        if(this.layoutDir != null){
            view.setLayoutDir(this.layoutDir);
        }
        if (this.layoutUrl != null) {
            view.setLayoutUrl(this.layoutUrl);
        }

        if (this.layoutKey != null) {
            view.setLayoutKey(this.layoutKey);
        }
        if (this.screenContentKey != null) {
            view.setScreenContentKey(this.screenContentKey);
        }
        return view;
    }
}

标签:java,spring,velocity

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