一个表单域自动绑定的Tag实现

package net.libo.web.taglib;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.Collection;
import java.util.Iterator;

import javax.servlet.jsp.JspException;
import javax.servlet.jsp.JspWriter;
import javax.servlet.jsp.tagext.BodyContent;
import javax.servlet.jsp.tagext.BodyTagSupport;

import org.apache.commons.beanutils.PropertyUtils;



import net.libo.web.util.HtmlEncoder;
import net.libo.web.util.HtmlUtils;



/**
 * @author Boyce
 * 
 */
public class FieldBindTag extends BodyTagSupport  {

    private Object[] beans = null;
    
    private String beanNames = null;
    
    /**
     * Sets bean names with value of the "bean" attribute.
     *
     * @param v      bean names
     */
    public void setBeans(String v) {
        beanNames = v;
    }
    /**
     * Gets bean names.
     *
     * @return bean names
     */
    public String getBeans() {
        return beanNames;
    }

    public int doStartTag() {
        String[] b = beanNames.split(",");
        ArrayList beanList = new ArrayList();
        for (int i=0;i            String name = b[i].trim();
            if (name.length() > 0) {
                Object bean = pageContext.findAttribute(name);     
                if (bean != null)beanList.add(bean);
            }
        }
        beans = beanList.toArray();
        return EVAL_BODY_AGAIN;
    }

    /**
     * Performs smart form population.
     *
     * @return SKIP_BODY
     */
    public int doAfterBody()  {
        BodyContent body = getBodyContent();
        try  {
            JspWriter out = body.getEnclosingWriter();
            String bodytext = body.getString();
            bodytext = populateForm(bodytext);
            out.print(bodytext);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        return SKIP_BODY;
    }


    /**
     * End of tag.
     *
     * @return EVAL_PAGE
     * @throws JspException 
     */
    public int doEndTag() throws JspException {
        beans = null;
        return EVAL_PAGE;
    }


 
        // ---------------------------------------------------------------- populate

        private String populateForm(String html) throws Exception {
                int i = 0, s = 0;
                StringBuffer result = new StringBuffer(html.length());
                String currentSelectName = null;
                while (true) {
                        // find starting tag
                        i =        html.indexOf('<', s);
                        if (i == -1) {
                                result.append(html.substring(s));
                                break;                // input tag not found
                        }
                        result.append(html.substring(s, i));        // tag found, all before tag is stored
                        s = i;

                        // find closing tag
                        i =        html.indexOf('>', i);
                        if (i == -1) {
                                result.append(html.substring(s));
                                break;                // closing tag not found
                        }
                        i++;

                        // match tags
                        String tag = html.substring(s, i);
            //System.out.println(tag);
            
                        String tagName = HtmlUtils.getTagName(tag);
                        if (tagName.equalsIgnoreCase("input") == true) {
                                String tagType = HtmlUtils.getAttribute(tag, "type");
                                if (tagType != null) {
                                        String name = HtmlUtils.getAttribute(tag, "name");
                    HashMap params = new HashMap();
                    params.put("name", name);
                    
                                        Object vobj = findValue(name);
                                        if (vobj != null) {
                                                String value = vobj.toString();
                                                tagType = tagType.toLowerCase();
                                                if (tagType.equals("text")) {
                                                        tag = HtmlUtils.addAttribute(tag, "value", value);
                                                } if (tagType.equals("hidden")) {
                                                        tag = HtmlUtils.addAttribute(tag, "value", value);
                                                } if (tagType.equals("image")) {
                                                        tag = HtmlUtils.addAttribute(tag, "value", value);
                                                } if (tagType.equals("password")) {
                                                        tag = HtmlUtils.addAttribute(tag, "value", value);
                                                } if (tagType.equals("checkbox")) {
                                                        String tagValue = HtmlUtils.getAttribute(tag, "value");
                                                        if (tagValue == null) {
                                                                tagValue = "true";
                                                        }
                                                        if (tagValue.equals(value)) {
                                                                tag = HtmlUtils.addAttribute(tag, "checked");
                                                        }
                                                } if (tagType.equals("radio")) {
                                                        String tagValue = HtmlUtils.getAttribute(tag, "value");
                                                        if (tagValue != null) {
                                                                if (tagValue.equals(value)) {
                                                                        tag = HtmlUtils.addAttribute(tag, "checked");
                                                                }
                                                        }
                                                }
                                        }
                                }
                        } else if (tagName.equalsIgnoreCase("textarea") == true) {
                                String name = HtmlUtils.getAttribute(tag, "name");
                                Object value = findValue(name);
                                if (value != null) {
                                        if (value != null) {
                                                tag += HtmlEncoder.encode(value.toString());
                                        }
                                }
                        } else if (tagName.equalsIgnoreCase("select") == true) {
                                currentSelectName = HtmlUtils.getAttribute(tag, "name");
                        } else if (tagName.equalsIgnoreCase("/select") == true) {
                                currentSelectName = null;
                        } else if (tagName.equalsIgnoreCase("option") == true) {
                                if (currentSelectName != null) {
                                        String tagValue = HtmlUtils.getAttribute(tag, "value");
                                        if (tagValue != null) {
                                                Object vals = findValue(currentSelectName);

                                                if (vals != null) {
                                                        if (vals.getClass().isArray()) {
                                                                Object[] arr = (Object[])vals;
                                                                if (arr.length > 0) {
                                                                        String[] vs = new String[arr.length];
                                                                        for (int j=0;j                                                                                vs[j] = arr[j].toString();
                                                                        }
                                                                        for (int k = 0; k < vs.length; k++) {
                                                                                String vsk = vs[k];
                                                                                if (vsk != null) {
                                                                                        if (vsk.equals(tagValue)) {
                                                                                                tag = HtmlUtils.addAttribute(tag, "selected");
                                                                                        }
                                                                                }
                                                                        }
                                                                }
                                                                
                                                        } else if (vals instanceof Collection) {
                                                                Collection arr = (Collection)vals;
                                                                int arrsize = arr.size();
                                                                if (arrsize > 0) {
                                                                        String[] vs = new String[arrsize];
                                                                        int j=0;
                                                                        for (Iterator it=arr.iterator();it.hasNext();) {
                                                                                vs[j++] = it.next().toString();
                                                                        }
                                                                        for (int k = 0; k < vs.length; k++) {
                                                                                String vsk = vs[k];
                                                                                if (vsk != null) {
                                                                                        if (vsk.equals(tagValue)) {
                                                                                                tag = HtmlUtils.addAttribute(tag, "selected");
                                                                                        }
                                                                                }
                                                                        }
                                                                }
                                                        } else {
                                                                String value = vals.toString();
                                                                if (value.equals(tagValue)) {
                                                                        tag = HtmlUtils.addAttribute(tag, "selected");
                                                                }
                                                        }
                                                }

                                        }
                                }
                        }
                        result.append(tag);
                        s = i;
                }
                return result.toString();
        }


    protected Object findValue(String name) {

        Object value = null;
        
        for (int i=0;i            
            if (beans[i] != null) {
                try {
                    value = PropertyUtils.getProperty(beans[i], name);
                } catch (Exception e) {
                }
                if (value != null) break;
            }
            
        }
        
        return value;
    }

}