OGNL表达式语言基础ABC

10月 9, 2012

OGNL表达式语言基础ABC

OGNL表达式语言能够帮助我们访问存在于ValueStack和ActionContext中的值.

首先让我们来看看通过OGNL来访问一个String数组的变量.在action类中我们创建一个string数组,代码如下:

package vaannila;

public class SampleAction {

    private  String[] sampleArray;
    {
    	sampleArray =  new String[]{"item1","item2","item3"};
    }
    public String execute()
    {
    	return "success";
    }
    public String[] getSampleArray() {
    	return sampleArray;
    }
    public void setSampleArray(String[] sampleArray) {
    	this.sampleArray = sampleArray;
    }
}

这样,在success中就能够通过下面的方式读取这个数组的值:

<b>Array Usage Examples</b>

<hr>
<b>sampleArray :</b> <s:property value="sampleArray"/> 

<b>sampleArray.length :</b> <s:property value="sampleArray.length"/> 

<b>sampleArray[0] :</b> <s:property value="sampleArray[0]"/> 

<b>[0].sampleArray :</b> <s:property value="[0].sampleArray"/> 

<b>top.sampleArray :</b> <s:property value="top.sampleArray"/>

下图就是页面的输出效果:

上面有三种方式能够获取到sampleArray.由于这个sampleArray是在这个stack的top.所以可以通过[0]或者top这个关键字来

直接取到.

下面看看怎么获取到一个ArrayList,在action类中创建一个ArrayList:

package vaannila;

import java.util.ArrayList;
import java.util.List;

public class SampleAction {

    private  List<String> sampleList = new ArrayList<String>();
    {
        sampleList.add("listItem1");
        sampleList.add("listItem2");
        sampleList.add("listItem3");
    }
    public String execute()
    {
    	return "success";
    }
    public List<String> getSampleList() {
    	return sampleList;
    }
    public void setSampleList(List<String> sampleList) {
    	this.sampleList = sampleList;
    }
}

同样可以通过下面的方式显示这个list:

<b>List Usage Examples</b>

<hr>
<b>sampleList :</b> <s:property value="sampleList"/> 

<b>sampleList.size :</b> <s:property value="sampleList.size"/> 

<b>sampleList[0] :</b> <s:property value="sampleList[0]"/>

下面再来看看怎么读取一个map类型的数据.通过在action类中创建一个map:

package vaannila;

import java.util.HashMap;
import java.util.Map;

public class SampleAction {

	private  Map<Integer,String> sampleMap = new HashMap<Integer,String>();
	private  String carMake;
	{
		sampleMap.put(new Integer(1), "one");
		sampleMap.put(new Integer(2), "two");
		sampleMap.put(new Integer(3), "three");
	}
	public String execute()
	{
		return "success";
	}
	public Map<Integer, String> getSampleMap() {
		return sampleMap;
	}
	public void setSampleMap(Map<Integer, String> sampleMap) {
		this.sampleMap = sampleMap;
	}
	public String getCarMake() {
		return carMake;
	}
	public void setCarMake(String carMake) {
		this.carMake = carMake;
	}

}

可以通过下面的方式来访问这个map:

<b>Map Usage Examples</b>

<hr>
<b>sampleMap[1] :</b> <s:property value="sampleMap[1]"/> 

<b>sampleMap.size :</b> <s:property value="sampleMap.size"/>

当然你可以直接在jsp中声明一个map:

<s:select list="#{'make1':'Ford', 'make2':'Honda', 'make3':'Toyota'}" name="carMake" label="Select "></s:select>

下面来看看怎么访问在action中model对象的属性name.代码如下:

package vaannila;

public class SampleAction {

    private  User user = new User();
    {
        user.setName("Eswar");
    }
    public String execute()
    {
        return "success";
    }

    public String getQuote()
    {
        return "Don't think, just do";
    }
    public User getUser() {
        return user;
    }
    public void setUser(User user) {
        this.user = user;
    }

}

可以通过下面的方式来访问:

<b>user.name :</b> <s:property value="user.name"/>

同样可以在jsp中直接调用action中的一个方法:

<b>quote() :</b> <s:property value="quote()"/>

OGNL Struts2

OGNL表达式语言基础ABC

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