使用ThreadLocal结合struts2的拦截器实现分页

1、定义PageModel类 

public class PageModel {
    private int total;
    private List datas;
    private int pageSize;
    private int offset;

    public int getPageSize() {
        return pageSize;
    }
    public void setPageSize(int pageSize) {
        this.pageSize = pageSize;
    }
    public int getOffset() {
        return offset;
    }
    public void setOffset(int offset) {
        this.offset = offset;
    }
    public int getTotal() {
        return total;
    }
    public void setTotal(int total) {
        this.total = total;
    }
    public List getDatas() {
        return datas;
    }
    public void setDatas(List datas) {
        this.datas = datas;
    }
}

2、定义ThreadLocal类 

public class MyThreadLocal {
    private static ThreadLocal tl = new ThreadLocal();

    public static void setValue(PageModel pm) {
        tl.set(pm);
    }

    public static PageModel getValue() {
        PageModel pm = (PageModel) tl.get();
        if(pm == null) {
            pm = new PageModel();
        }
        return pm;
    }

    public static  void remove() {
        tl.remove();
    }
}

3、定义我们自己的拦截器 

public class PageModelInterceptor extends AbstractInterceptor {

    @Override
    public String intercept(ActionInvocation invoke) throws Exception {
        int offset = 0;
        try {
            offset = Integer.parseInt(ServletActionContext.getRequest()
                    .getParameter("pager.offset"));
        } catch (NumberFormatException e) {
        }
        int pageSize = 5;
        PageModel pm = MyThreadLocal.getValue();
        pm.setOffset(offset<0 ? 0 : offset);
        pm.setPageSize(pageSize<0 ? Integer.MAX_VALUE : pageSize);
                  //将pagemodel中相关的分页数据设置好之后放到Threadlocal中
//在后台进行查询的时候从ThreadLocal中取出PageModel对象然后使用分页数据即可。
        MyThreadLocal.setValue(pm);
        try {
            return invoke.invoke();
        }finally {
//注意等到整个拦截器执行完成即一个ThreadLocal完成它的工作后要清除里面的内容
            MyThreadLocal.remove();
        }
    }
}

4、在struts.xml配置文件中加入我们的拦截器 

<interceptors>
<!--定义拦截器 -->
    <interceptor name="pageModelInterceptor" class="com.bjsxt.oa.util.PageModelInterceptor"/>
              <interceptor-stack name="myInterceptorStack">
                <interceptor-ref name="exception"/>
<!--加入我们自己定义的拦截器，在拦截器中把分页数据设置到ThreadLocal里然后再dao层取出用于分页 -->
                <interceptor-ref name="pageModelInterceptor"/>
                <interceptor-ref name="alias"/>
                <interceptor-ref name="servletConfig"/>
                <interceptor-ref name="i18n"/>
                <interceptor-ref name="prepare"/>
                <interceptor-ref name="chain"/>
                <interceptor-ref name="debugging"/>
                <interceptor-ref name="scopedModelDriven"/>
                <interceptor-ref name="updatableInterceptor"/>
                <interceptor-ref name="modelDriven"/>
                <interceptor-ref name="fileUpload"/>
                <interceptor-ref name="checkbox"/>
                <interceptor-ref name="multiselect"/>
                <interceptor-ref name="staticParams"/>
                <interceptor-ref name="actionMappingParams"/>
                <interceptor-ref name="params">
                  <param name="excludeParams">dojo\..*,^struts\..*,pager.offset</param>
                </interceptor-ref>
                <interceptor-ref name="conversionError"/>
                <interceptor-ref name="validation">
                    <param name="excludeMethods">input,back,cancel,browse</param>
                </interceptor-ref>
                <interceptor-ref name="workflow">
                    <param name="excludeMethods">input,back,cancel,browse</param>
                </interceptor-ref>
            </interceptor-stack>
        </interceptors>

<default-interceptor-ref name="myInterceptorStack"/>