在JSP页面中使用自定义标记调用javabean的方法
不知道大家在调用JavaBean的方法时，是不是像我一样感觉很是不爽？看下面这段代码：
<jsp:useBean id="memberBean" class="org.jforum.bbean.MemberBean" scope="session"></jsp:useBean><c:choose> <c:when test="${param.Submit=='注 销'}"> <% memberBean.loginOut(); %> <c:redirect url="index.jsp" /> </c:when> <c:when test="${param.Submit=='登 录'}"> <% memberBean.login(request.getParameter("username"), request.getParameter("password")); %> <c:if test="${memberBean.logined}"> <c:redirect url="index.jsp" /> </c:if> </c:when></c:choose>
<% memberBean.login(request.getParameter("username"), request.getParameter("password")); %>
自己写出来，都觉得很费力！
但是还有更糟的：
<ul> <c:forEach items="${categoryBean.categoryList}" var="category"> <li>${ category.name }</li> <ul> <c:forEach items="<%= categoryBean.getSubCategoryList((Category)pageContext.getAttribute("category")) %>" var="subCategory"> <li> <a href="category.jsp?id=${ subCategory.id }">${ subCategory.name }</a><br /> ${ subCategory.description } </li> </c:forEach> </ul> </c:forEach> </ul>
大家都看到了：<% %>中想要使用标签库定义的对象真是痛苦！
我只是恨JSP2没有调用javabean方法的标签！！！（该死的JSP，总有一天要淘汰你。）
但是想想要通过反射调用bean的方法应该也不是什么难事，就自己翻参考书写了两个标签解决了这个问题！
现将成果公布一下，和大家分享！
主要的标记处理代码：Call.java
/* * Call.java * * Created on June 11, 2007, 12:03 PM */package learnjsp2.tags;import java.lang.reflect.InvocationTargetException;import java.lang.reflect.Method;import java.util.ArrayList;import java.util.Iterator;import java.util.List;import javax.servlet.jsp.PageContext;import javax.servlet.jsp.tagext.*;import javax.servlet.jsp.JspWriter;import javax.servlet.jsp.JspException;import org.apache.taglibs.standard.lang.jstl.Coercions;import org.apache.taglibs.standard.lang.jstl.ELException;/** * * @authorzsun * @version */public class Call extends SimpleTagSupport implements DynamicAttributes, StrictTypeParams{ /** * Initialization of bean property. */ private java.lang.Object bean; /** * Initialization of method property. */ private java.lang.String method; /** * Initialization of var property. */ private java.lang.String var = null; /** * Initialization of scope property. */ private int scope = PageContext.PAGE_SCOPE; private List dynamicAttrValues = new ArrayList(); private List typeList = null; /**Called by the container to invoke this tag. * The implementation of this method is provided by the tag library developer, * and handles all tag processing, body iteration, etc. */ public void doTag() throws JspException { JspWriter out=getJspContext().getOut(); try { JspFragment f=getJspBody(); if (f != null) f.invoke(out); } catch (java.io.IOException ex) { throw new JspException(ex.getMessage()); } Class cls = bean.getClass(); Method[] methods = cls.getMethods(); Method m = null; Class[] paramTypes = null; search: for (int i = 0; i < methods.length; i++ ) { Method t = methods; paramTypes = t.getParameterTypes(); if (t.getName().equals(method) && paramTypes.length == dynamicAttrValues.size()) { if (typeList != null) for (int j = 0; j < paramTypes.length; j++) if (!paramTypes.getName().equals(typeList.get(j))) continue search; m = t; break; } } if (m == null) throw new JspException("JavaBean Object hasn't no method named '" + method + "'"); try { Object coercedValues[] = new Object; Iterator paramIterator = dynamicAttrValues.iterator(); for (int i = 0; i < paramTypes.length; i++) { Object paramValue = paramIterator.next(); Class paramClass = paramTypes; System.out.println(paramClass); if (paramValue == null || paramValue.getClass() != paramClass) try { paramValue = Coercions.coerce(paramValue, paramClass, null); } catch (ELException e) { throw new JspException(e.getMessage(), e.getRootCause()); } coercedValues = paramValue; } Object returnVal = m.invoke(bean, coercedValues); if (var != null) if (returnVal != null) getJspContext().setAttribute(var, returnVal, scope); else getJspContext().removeAttribute(var, scope); } catch (Exception ex) { ex.printStackTrace(); throw new JspException("Call method is Error!"); } } /** * Setter for the bean attribute. */ public void setBean(java.lang.Object value) throws JspException { if (value == null) throw new JspException("Null 'bean' attribute in 'Call' tag"); this.bean = value; } /** * Setter for the method attribute. */ public void setMethod(java.lang.String value) throws JspException { if (value == null) throw new JspException("Null 'method' attribute in 'Call' tag"); this.method = value; } /** * Setter for the var attribute. */ public void setVar(java.lang.String value) throws JspException { if (value == null) throw new JspException("Null 'var' attribute in 'Call' tag"); this.var = value; } /** * Setter for the scope attribute. */ public void setScope(java.lang.String value) { if (value.equalsIgnoreCase("page")) scope = PageContext.PAGE_SCOPE; else if (value.equalsIgnoreCase("request")) scope = PageContext.REQUEST_SCOPE; else if (value.equalsIgnoreCase("session")) scope = PageContext.SESSION_SCOPE; else if (value.equalsIgnoreCase("application")) scope = PageContext.APPLICATION_SCOPE; } public void setDynamicAttribute(String uri, String localName, Object value) throws JspException { dynamicAttrValues.add(value); } public void addStrictTypeParameter(String type, Object value) { if (typeList == null) typeList = new ArrayList(); typeList.add(type); dynamicAttrValues.add(value); }}
定义父子标签协作接口：StrictTypeParams.java
/* * StrictTypeParams.java * * Created on June 14, 2007, 9:35 AM * * To change this template, choose Tools | Template Manager * and open the template in the editor. */package learnjsp2.tags;/** * * @author zsun */public interface StrictTypeParams { void addStrictTypeParameter(String type, Object value);}
参数标记：ParamTag.java
package learnjsp2.tags;/* * ParamTag.java * * Created on June 14, 2007, 10:35 AM */import javax.servlet.jsp.tagext.*;import javax.servlet.jsp.JspWriter;import javax.servlet.jsp.JspException;/** * * @authorzsun * @version */public class ParamTag extends SimpleTagSupport { /** * Initialization of class property. */ private java.lang.String _class; /**Called by the container to invoke this tag. * The implementation of this method is provided by the tag library developer, * and handles all tag processing, body iteration, etc. */ public void doTag() throws JspException { StrictTypeParams parent = (StrictTypeParams)findAncestorWithClass(this, StrictTypeParams.class); if (parent == null) { throw new JspException("The Param tag is not enclosed by a supported tag type"); } parent.addStrictTypeParameter(this._class, this.value); } /** * Initialization of value property. */ private java.lang.Object value; /** * Setter for the class attribute. */ public void setParamclass(java.lang.String value) { this._class = value; } /** * Setter for the value attribute. */ public void setValue(java.lang.Object value) { this.value = value; }}
部署描述符：
<?xml version="1.0" encoding="UTF-8"?><taglib version="2.0" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee web-jsptaglibrary_2_0.xsd"><tlib-version>1.0</tlib-version><short-name>utils</short-name><uri>/WEB-INF/tlds/utils</uri><tag> <name>Call</name> <tag-class>learnjsp2.tags.Call</tag-class> <body-content>scriptless</body-content> <attribute> <name>bean</name> <required>true</required> <rtexprvalue>true</rtexprvalue> <type>java.lang.Object</type> </attribute> <attribute> <name>method</name> <required>true</required> <rtexprvalue>true</rtexprvalue> <type>java.lang.String</type> </attribute> <attribute> <name>var</name> <rtexprvalue>true</rtexprvalue> <type>java.lang.String</type> </attribute> <attribute> <name>scope</name> <rtexprvalue>true</rtexprvalue> <type>java.lang.String</type> </attribute> <dynamic-attributes>true</dynamic-attributes></tag><tag> <name>Param</name> <tag-class>learnjsp2.tags.ParamTag</tag-class> <body-content>empty</body-content> <attribute> <name>paramclass</name> <required>true</required> <rtexprvalue>true</rtexprvalue> <type>java.lang.String</type> </attribute> <attribute> <name>value</name> <required>true</required> <rtexprvalue>true</rtexprvalue> <type>java.lang.Object</type> </attribute></tag></taglib>
页:
[1]