自定义标签：在JSP页面中动态实施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。

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一、java源代码

??? 1、ServiceTag源代码

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;
	}
}

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??? 2、ServiceParamTag源代码

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;
	}
}

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??? 3、公共方法源代码

//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;
}

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二、tld文件源代码

<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>

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三、范例

??? 1、java源代码

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

<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"/>

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