自定义标签：在JSP页面中动态执行Spring Bean的方法

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自定义标签：在JSP页面中动态执行Spring Bean的方法

使用该自定义标签，可以在JSP页面中动态执行某个Spring Bean对象的一个方法，方法返回的结果存储在ValueStack中。该自定义标签在Spring2、Struts2、Hibernate3环境下测试通过。

一、java源代码

1、ServiceTag源代码

Java代码

public class ServiceTag extends BaseBodyTagSupport {private String beanName;private String methodName;private String id;public List params = new ArrayList();public void setBeanName(String beanName) {this.beanName = beanName;}public void setMethodName(String methodName) {this.methodName = methodName;}public void setId(String id) {this.id = id;}public int doEndTag() throws JspException {Object bean = null;Method method = null;//取得bean对象try{bean = SpringContextUtil.getBean(beanName);}catch(Exception ex){throw new JspException("get bean error: " + beanName);}//通过反射取得方法if(bean != null){try {method = bean.getClass().getMethod(methodName, TagUtil.getParameterTypes(params));}catch(Exception e) {throw new JspException("get method error: " + beanName + "." + methodName);}}else{throw new JspException("ServiceTag Error: bean [" + beanName + "] is null");}//通过反射执行方法，得到结果Object result = null;if(method != null){try {result = method.invoke(bean, TagUtil.getParameterValues(params));}catch(Exception e){throw new JspException("method invoke error");}}//将结果存储在ValueStack中ValueStack vs = TagUtils.getStack(pageContext);vs.getContext().put(id, result);return EVAL_PAGE;}}

2、ServiceParamTag源代码

Java代码

public class ServiceParamTag extends BaseBodyTagSupport {private String name;private Object value;private String type;public void setName(String name) {this.name = name;}public void setValue(Object value) {this.value = value;}public void setType(String type) {this.type = type;}public int doEndTag() throws JspException {Tag parent = getParent();if(parent instanceof ServiceTag){Map p = new HashMap();p.put("paramName", name);p.put("paramValue", value);p.put("paramType", type);((ServiceTag)parent).params.add(p);}return EVAL_PAGE;}}

3、公共方法源代码

Java代码

//参数类型数组public static Class[] getParameterTypes(List params) throws Exception{Class[] c = new Class[params.size()];for(int i=0;i<params.size();i++){Map p = (Map)params.get(i);String type = (String)p.get("paramType");c[i] = Class.forName(type);}return c;}//参数值数组public static Object[] getParameterValues(List params) throws Exception{Object[] o = new Object[params.size()];for(int i=0;i<params.size();i++){Map p = (Map)params.get(i);o[i] = p.get("paramValue");}return o;}

<pre>
* 一定要在spring.xml中加上:
* <bean id="SpringContextUtil " class="com.hmw.spring.SpringContextUtil" singleton="true" />
* 当对SpringContextUtil 实例时就自动设置applicationContext,以便后来可直接用applicationContext
* </pre>

package org.company.xxx;
import org.springframework.beans.BeansException;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
/**
*
* 获取spring容器，以访问容器中定义的其他bean
* @author lyltiger
* @since MOSTsView 3.0 2009-11-16
*/
public class SpringContextUtil implements ApplicationContextAware {
// Spring应用上下文环境
private static ApplicationContext applicationContext;
/**
* 实现ApplicationContextAware接口的回调方法，设置上下文环境
*
* @param applicationContext
*/
public void setApplicationContext(ApplicationContext applicationContext) {
SpringContextUtil.applicationContext = applicationContext;
}
/**
* @return ApplicationContext
*/
public static ApplicationContext getApplicationContext() {
return applicationContext;
}
/**
* 获取对象
* 这里重写了bean方法，起主要作用
* @param name
* @return Object 一个以所给名字注册的bean的实例
* @throws BeansException
*/
public static Object getBean(String name) throws BeansException {
return applicationContext.getBean(name);
}
}

二、tld文件源代码

Xml代码

<tag><name>serviceBean</name><tag-class>com.cjm.web.taglib.ServiceTag</tag-class><body-content>JSP</body-content><attribute><name>beanName</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute><attribute><name>methodName</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute><attribute><name>id</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute></tag><tag><name>serviceParam</name><tag-class>com.cjm.web.taglib.ServiceParamTag</tag-class><body-content>JSP</body-content><attribute><name>name</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute><attribute><name>value</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute><attribute><name>type</name><required>true</required><rtexprvalue>true</rtexprvalue></attribute></tag>

三、范例

1、java源代码

Java代码

public class RoleService extends BaseService {private RoleDao roleDao;public RoleDao getRoleDao() {return roleDao;}public void setRoleDao(RoleDao roleDao) {this.roleDao = roleDao;}public Role getRole(String roleId){return (Role)get(Role.class, roleId);}}

2、JSP页面源代码

Html代码

<cjm:serviceBean beanName="roleService" methodName="getRole" id="result">
<cjm:serviceParam name="roleId" value="ADMIN" type="java.lang.String"/>
</cjm:serviceBean>
<s:property value="#result.roleName"/>