struts_config.xml之plug-in

 

struts_config.xml之plug-in

plug-in设置主要是用于和第三方代码的扩展。现举例说明。
1.假设我们有一个login.jsp文件的表单需要提交到server
<form action="login.do">
name<input type="text" name="name">
password<input type="text" name="password">
birthday<input type="text" name="birthday">
<input type="submit" value="提交">
</form>
2.对应的javabean文件
import java.util.Date;
import org.apache.struts.action.ActionForm;
public class LoginForm extends ActionForm {
private String name;
private String password;
private Date birthday;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
}
3.对应的Action类
public class LoginAction extends Action {
public ActionForward execute(ActionMapping mapping, ActionForm form,
HttpServletRequest request, HttpServletResponse response)
throws Exception {
return mapping.findForward("success");
}
}
4.struts-config.xml配置
<struts-config>
    <form-beans>
    <form-bean name="login" type="LoginForm"></form-bean>
    </form-beans>
    <action-mappings>
    <action name="login" path="/login" type="LoginAction" scope="request">
    <forward name="success" path="/login_result.jsp"></forward>
    </action>
    </action-mappings>
    <message-resources parameter="MessageResources" />
</struts-config>
6.页面显示文件login_result.jsp
${login.name }
${login.password }
${login.birthday }


当你运行的时候进入login_result.jsp会发现jvm会报错。因为jvm会根据输入数据自动转变为javabean中对应的类型，但是仅仅限于基本数据类型。请参考Struts的ActionServlet源码

if (convertNull) {
            ConvertUtils.deregister();
            ConvertUtils.register(new BigDecimalConverter(null), BigDecimal.class);
            ConvertUtils.register(new BigIntegerConverter(null), BigInteger.class);
            ConvertUtils.register(new BooleanConverter(null), Boolean.class);
            ConvertUtils.register(new ByteConverter(null), Byte.class);
            ConvertUtils.register(new CharacterConverter(null), Character.class);
            ConvertUtils.register(new DoubleConverter(null), Double.class);
            ConvertUtils.register(new FloatConverter(null), Float.class);
            ConvertUtils.register(new IntegerConverter(null), Integer.class);
            ConvertUtils.register(new LongConverter(null), Long.class);
            ConvertUtils.register(new ShortConverter(null), Short.class);
        }
而 birthday是Date类型。struts没有对date类型，不会自动转换，所以我们要扩展ActionServlet，对date类型经行转换
1.建立DateConverter 继承 Converter
public class DateConverter implements Converter {
public Object convert(Class type, Object value) {
// TODO Auto-generated method stub
if (value==null) {
return null;
}
if (value instanceof Date) {
return value;
}
Date d=null;
if (value instanceof String) {
if (!"".equals(value)) {
SimpleDateFormat sf = new SimpleDateFormat("yyyy-mm-dd");
d = sf.parse((String) value);
}
}
return d;
}
}


2.在web.xml中注册继承的扩展类
注册方法1
1.建立ActionServlet，重写initother方法

public class ActionServlet extends org.apache.struts.action.ActionServlet {

protected void initOther() throws ServletException {
// TODO Auto-generated method stub
super.initOther();
ConvertUtils.register(new DateConverter(), java.util.Date.class);
}
}
2.将<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>修改为<servlet-class>ActionServlet</servlet-class>
注册方法2
1.新建TestActionServlet继承ActionServlet
  public class TestActionServlet extends ActionServlet {
protected void initOther() throws ServletException {
// TODO Auto-generated method stub
super.initOther();
ConvertUtils.register(new DateConverter(), java.util.Date.class);
}
}
2.在Struts_config.xml文件中
<plug-in className="TestActionServlet">
</plug-in>

这样程序就能正常运行了。

题外话：
el表达式${login.birthday }可以用jstl标签对其经行格式化<fmt:formatDate value="${login.birthday}"/>