JAVA: OGNL expression practice

1. OGNL expression

1. Introduction

OGNL: Object view navigation language. ${user.addr.name} This way of writing is called an object View navigation.
OGNL can not only view navigation, but also supports richer functions than EL expressions.

2. Use OGNL to prepare work

2.1 Import package

The struts2 package is already included, so there is no need to import additional jar packages

　2.2 Code preparation

　

##

    @Test//准备工作public void fun1() throws Exception{//准备OGNLContext//准备RootUser rootUser = new User("tom",18);//准备ContextMap<String,User> context = new HashMap<String,User>();
            context.put("user1", new User("jack",18));
            context.put("user2", new User("rose",22));
        OgnlContext oc = new OgnlContext();//将rootUser作为root部分        oc.setRoot(rootUser);//将context这个Map作为Context部分        oc.setValues(context);//书写OGNLOgnl.getValue("", oc, oc.getRoot());
    }

Preparation work

　3. Basic syntax demonstration

        //取出root中user对象的name属性String name = (String) Ognl.getValue("name", oc, oc.getRoot());
        Integer age = (Integer) Ognl.getValue("age", oc, oc.getRoot());
        System.out.println(name);
        System.out.println(age);

Get the attribute value in root

        //取出context中键为user1对象的name属性String name = (String) Ognl.getValue("#user1.name", oc, oc.getRoot());
        String name2 = (String) Ognl.getValue("#user2.name", oc, oc.getRoot());
        Integer age = (Integer) Ognl.getValue("#user2.age", oc, oc.getRoot());
        System.out.println(name);
        System.out.println(name2);
        System.out.println(age);

Get the attribute value in context

        //将root中的user对象的name属性赋值Ognl.getValue("name='jerry'", oc, oc.getRoot());
        String name = (String) Ognl.getValue("name", oc, oc.getRoot());
        
        String name2 = (String) Ognl.getValue("#user1.name='郝强勇',#user1.name", oc, oc.getRoot());
        System.out.println(name);
        System.out.println(name2);

Assign a value to the attribute

        //调用root中user对象的setName方法Ognl.getValue("setName('lilei')", oc, oc.getRoot());
        String name = (String) Ognl.getValue("getName()", oc, oc.getRoot());
        String name2 = (String) Ognl.getValue("#user1.setName('lucy'),#user1.getName()", oc, oc.getRoot());
        
        System.out.println(name);
        System.out.println(name2);

Call method

        String name = (String) Ognl.getValue("@cn.itheima.a_ognl.HahaUtils@echo('hello 强勇!')", oc, oc.getRoot());//Double pi = (Double) Ognl.getValue("@java.lang.Math@PI", oc, oc.getRoot());Double pi = (Double) Ognl.getValue("@@PI", oc, oc.getRoot());
        System.out.println(name);
        System.out.println(pi);

Call static method

        //创建list对象Integer size = (Integer) Ognl.getValue("{'tom','jerry','jack','rose'}.size()", oc, oc.getRoot());
        String name = (String) Ognl.getValue("{'tom','jerry','jack','rose'}[0]", oc, oc.getRoot());
        String name2 = (String) Ognl.getValue("{'tom','jerry','jack','rose'}.get(1)", oc, oc.getRoot());    /*System.out.println(size);
        System.out.println(name);
        System.out.println(name2);*///创建Map对象Integer size2 = (Integer) Ognl.getValue("#{'name':'tom','age':18}.size()", oc, oc.getRoot());
        String name3  = (String) Ognl.getValue("#{'name':'tom','age':18}['name']", oc, oc.getRoot());
        Integer age  = (Integer) Ognl.getValue("#{'name':'tom','age':18}.get('age')", oc, oc.getRoot());
        System.out.println(size2);
        System.out.println(name3);
        System.out.println(age);

ognlCreate object-list|map

 

二、OGNL与Struts2的结合

 

　　1.结合原理

　　

　　ValueStack中的两部分

　　

 

　　2.栈原理

　　

　　栈是由ArrayList模拟的

　　

　　栈中的两个方法的实现

　　

　　访问栈中属性的特点.由上到下

　　

 

　　3.查看值栈中两部分内容(使用DEBUG标签)

　　 3.1Root

　　默认情况下,栈中放置当前访问的Action对象

　　

　　3.2Context

　　

　　

　　Context部分就是ActionContext数据中心

 

 　　4.struts2与ognl结合体现

　　  4.1参数接收

    　

  

　　　　如何获得值栈对象,值栈对象与ActionContext对象是互相引用的

        //压入栈顶//1获得值栈ValueStack vs = ActionContext.getContext().getValueStack();//2将u压入栈顶vs.push(u);

　　  4.2配置文件中

<action name="Demo3Action" class="cn.itheima.d_config.Demo3Action" method="execute" ><result name="success" type="redirectAction" ><param name="actionName">Demo1Action</param><param name="namespace">/</param><!-- 如果添加的参数struts"看不懂".就会作为参数附加重定向的路径之后.
                     如果参数是动态的.可以使用${}包裹ognl表达式.动态取值                 --><param name="name">${name}</param></result></action>

语法:${ognl表达式}

 

　　5.扩展:request对象的getAttribute方法

　　　查找顺序：

　　

 

三、练习:客户列表

    public String list() throws Exception {//1 接受参数String cust_name = ServletActionContext.getRequest().getParameter("cust_name");//2 创建离线查询对象DetachedCriteria dc =DetachedCriteria.forClass(Customer.class);//3 判断参数拼装条件if(StringUtils.isNotBlank(cust_name)){
            dc.add(Restrictions.like("cust_name", "%"+cust_name+"%"));
        }//4 调用Service将离线对象传递List<Customer> list = cs.getAll(dc);//5 将返回的list放入request域.转发到list.jsp显示        //ServletActionContext.getRequest().setAttribute("list", list);// 放到ActionContextActionContext.getContext().put("list", list);        return "list";
    }

Action代码（新增ActionContext存放数据）

<s:iterator value="#list" var="cust" >
    <TR         
        style="FONT-WEIGHT: normal; FONT-STYLE: normal; BACKGROUND-COLOR: white; TEXT-DECORATION: none">
        <TD>
            <s:property value="#cust.cust_name" />
        </TD>
        <TD>
        <s:property value="#cust.cust_level" />
        </TD>
        <TD>
        <s:property value="#cust.cust_source" />
        </TD>
        <TD>
        <s:property value="#cust.cust_linkman" />
        </TD>
        <TD>
        <s:property value="#cust.cust_phone" />
        </TD>
        <TD>
        <s:property value="#cust.cust_mobile" />
        </TD>
        <TD>
        <a href="${pageContext.request.contextPath }/customerServlet?method=edit&custId=${customer.cust_id}">修改</a>
          <a href="${pageContext.request.contextPath }/customerServlet?method=delete&custId=${customer.cust_id}">删除</a>
        </TD>
    </TR>
    </s:iterator>
    <%-- <s:iterator value="#list"  >
    <TR         
        style="FONT-WEIGHT: normal; FONT-STYLE: normal; BACKGROUND-COLOR: white; TEXT-DECORATION: none">
        <TD>
            <s:property value="cust_name" />
        </TD>
        <TD>
        <s:property value="cust_level" />
        </TD>
        <TD>
        <s:property value="cust_source" />
        </TD>
        <TD>
        <s:property value="cust_linkman" />
        </TD>
        <TD>
        <s:property value="cust_phone" />
        </TD>
        <TD>
        <s:property value="cust_mobile" />
        </TD>
        <TD>
        <a href="${pageContext.request.contextPath }/customerServlet?method=edit&custId=${customer.cust_id}">修改</a>
          <a href="${pageContext.request.contextPath }/customerServlet?method=delete&custId=${customer.cust_id}">删除</a>
        </TD>
    </TR>
    </s:iterator> --%>

JSP显示数据的代码（注释的是另一种方法）

 注意： 每次都会把cust存在ActionContext中

 

The above is the detailed content of JAVA: OGNL expression practice. For more information, please follow other related articles on the PHP Chinese website!