用测试理解怎么使用ognl： 读取和设置包含筛选条件的列表元素的属性

先转一篇介绍

OGNL 语言介绍与实践 

官网上的资料比较精炼，例子很少，还是写一些测试代码来验证用法：

包装一下：

package org.airlinkmatrix.test.ognl;

import ognl.Ognl;
import ognl.OgnlContext;
import ognl.OgnlException;

public class OgnlExpression {
	
	private static final OgnlContext DEFAULT_CONTEXT = (OgnlContext)Ognl.createDefaultContext(null);
	
	private Object expression;
	private OgnlContext context;

	public void setContext(OgnlContext context) {
		this.context = context;
	}

	public OgnlContext getContext() {
		if (context==null){
			context = DEFAULT_CONTEXT;
		}
		return context;
	}
	
	public OgnlExpression(String expressionString) throws OgnlException
	{
		super();
		expression = Ognl.parseExpression(expressionString);
	}

	public Object getExpression()
	{
		return expression;
	}

	public Object getValue(Object rootObject) throws OgnlException
	{
		return Ognl.getValue(getExpression(), getContext(), rootObject);
	}

	public void setValue(Object rootObject, Object value) throws OgnlException
	{
		Ognl.setValue(getExpression(), getContext(), rootObject, value);
	}

}

 测试类：

package org.airlinkmatrix.test.ognl;

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

import org.airlinkmatrix.test.ognl.OgnlExpression;

import junit.framework.TestCase;
import ognl.OgnlException;

public class OgnlExpressionTest extends TestCase {

	class Root{
		private Object[] array;
		public Object[] getArray() {
			return array;
		}
		public void setArray(Object[] array) {
			this.array = array;
		}
		
		private Vector vector;
		public Vector getVector() {
			return vector;
		}
		public void setVector(Vector vector) {
			this.vector = vector;
		}
		public Root() {
			vector = new Vector();
			vector.add(new Part("Michael","002"));
			vector.add(new Part("Alex","001"));
			vector.add(new Part("Joseph","003"));
			vector.add(new Part("Alex","004"));
			
			array = new Part[4];
			array[0] = new Part("Michael","002");
			array[1] = new Part("Alex","001");
			array[2] = new Part("Joseph","003");
			array[3] = new Part("Alex","004");
		}
	}
	
	class Part{
		private String id;
		public String getId() {
			return id;
		}

		public void setId(String id) {
			this.id = id;
		}

		private String name;

		public Part(String name,String id) {
			super();
			this.name = name;
			this.id = id;
		}

		public String getName() {
			return name;
		}

		public void setName(String name) {
			this.name = name;
		}

		public String toString() {
//			return "name='"+name+"',id='"+id+"'";
			return name;
		}

		public boolean equals(Object obj) {
			if (!(obj instanceof Part)){
				return false;
			}
			Part anotherPart = (Part)obj;
			if (this.name==null||this.id==null){
				return false;
			}
			if (!this.name.equals(anotherPart.getName())){
				return false;
			}
			if (!this.id.equals(anotherPart.getId())){
				return false;
			}
			return true;
		}
		
	}
	
	private Root ROOT;

	protected void setUp() throws Exception {
		super.setUp();
		ROOT = new Root();
	}

	protected void tearDown() throws Exception {
		super.tearDown();
	}
	
	public void testGetValue_ROOT_vector() {
		try {
			OgnlExpression expression = null;
			ArrayList valueList = null;
			
			//?号表示匹配所有记录，
			expression = new OgnlExpression("vector.{? #this.name == 'Alex' }");
			valueList = (ArrayList)expression.getValue(ROOT);
			assertEquals(new Part("Alex","001"),valueList.get(0));
			assertEquals(new Part("Alex","004"),valueList.get(1));
			
			//^号表示匹配第一条记录
			expression = new OgnlExpression("vector.{^ #this.name == 'Alex' }");
			valueList = (ArrayList)expression.getValue(ROOT);
			assertEquals(new Part("Alex","001"),valueList.get(0));

			//$号表示匹配最后一条记录
			expression = new OgnlExpression("vector.{$ #this.name == 'Alex' }");
			valueList = (ArrayList)expression.getValue(ROOT);
			assertEquals(new Part("Alex","004"),valueList.get(0));

			//?号匹配多条记录，所以有可能选到第二条记录
			expression = new OgnlExpression("vector.{? #this.name == 'Alex' }[1].id");
			assertEquals("004",expression.getValue(ROOT));

			//可以接着取记录属性
			expression = new OgnlExpression("vector.{^ #this.name == 'Alex' }[0].id");
			assertEquals("001",expression.getValue(ROOT));

			try{
				//^号匹配单条记录，第二条记录一定是空的，会报IndexOutOfBoundsException
				expression = new OgnlExpression("vector.{^ #this.name == 'Alex' }[1].id");
				expression.getValue(ROOT);
				fail("expect IndexOutOfBoundsException");
			}catch (IndexOutOfBoundsException ex){
				
			}catch (Exception otherEx){
				fail("expect IndexOutOfBoundsException");
			}
			
			try{
				//^号匹配单条记录，如果匹配不到数据，仍然会报IndexOutOfBoundsException
				//这个与官网的文档是有出入的，^号并不能避免IndexOutOfBoundsException
				expression = new OgnlExpression("vector.{^ #this.name == 'Wrong Name' }[0].id");
				expression.getValue(ROOT);
				fail("expect IndexOutOfBoundsException");
			}catch (IndexOutOfBoundsException ex){
				
			}catch (Exception otherEx){
				fail("expect IndexOutOfBoundsException");
			}
			
		} catch (OgnlException e) {
			e.printStackTrace();
			fail("oops!");
		}
	}

	
	public void testGetValue_ROOT_array() {
		
		try {
			OgnlExpression expression = null;
			ArrayList valueList = null;
			
			//?号表示匹配所有记录，
			expression = new OgnlExpression("array.{? #this.name == 'Alex' }");
			valueList = (ArrayList)expression.getValue(ROOT);
			assertEquals(new Part("Alex","001"),valueList.get(0));
			assertEquals(new Part("Alex","004"),valueList.get(1));
			
			//^号表示匹配第一条记录
			expression = new OgnlExpression("array.{^ #this.name == 'Alex' }");
			valueList = (ArrayList)expression.getValue(ROOT);
			assertEquals(new Part("Alex","001"),valueList.get(0));

			//$号表示匹配最后一条记录
			expression = new OgnlExpression("array.{$ #this.name == 'Alex' }");
			valueList = (ArrayList)expression.getValue(ROOT);
			assertEquals(new Part("Alex","004"),valueList.get(0));

			//?号匹配多条记录，所以有可能选到第二条记录
			expression = new OgnlExpression("array.{? #this.name == 'Alex' }[1].id");
			assertEquals("004",expression.getValue(ROOT));

			//可以接着取记录属性
			expression = new OgnlExpression("array.{^ #this.name == 'Alex' }[0].id");
			assertEquals("001",expression.getValue(ROOT));

			try{
				//^号匹配单条记录，第二条记录一定是空的，会报IndexOutOfBoundsException
				expression = new OgnlExpression("array.{^ #this.name == 'Alex' }[1].id");
				expression.getValue(ROOT);
				fail("expect IndexOutOfBoundsException");
			}catch (IndexOutOfBoundsException ex){
				
			}catch (Exception otherEx){
				fail("expect IndexOutOfBoundsException");
			}
			
			try{
				//^号匹配单条记录，如果匹配不到数据，仍然会报IndexOutOfBoundsException
				//这个与官网的文档是有出入的，^号并不能避免IndexOutOfBoundsException
				expression = new OgnlExpression("array.{^ #this.name == 'Wrong Name' }[0].id");
				expression.getValue(ROOT);
				fail("expect IndexOutOfBoundsException");
			}catch (IndexOutOfBoundsException ex){
				
			}catch (Exception otherEx){
				fail("expect IndexOutOfBoundsException");
			}
			
		} catch (OgnlException e) {
			e.printStackTrace();
			fail("oops!");
		}
	}
	
	public void testSetValue_ROOT_Normal() {
		
		try {
			OgnlExpression expression = null;
			
			expression = new OgnlExpression("array.{^ #this.name == 'Alex' }[0].id");
			expression.setValue(ROOT,"007");
			
			assertEquals("007",((Part)ROOT.getArray()[1]).getId());
			
		} catch (OgnlException e) {
			e.printStackTrace();
			fail("oops!");
		}
	}
	
	
}

读取、设置对象图内部的一个值没有多大问题了。但，ognl 组件是否能够配置为设置列表中每一个元素的某字段为同一值呢？

例如，对象图如下：

ROOT

   Part

     id="1"

   Part

     id="2"

   Part

     id="3"

其中ROOT拥有Part的一个列表(java.util.List)

有没有一种写法，能利用ognl表达式一次将上述对象的值改为：

ROOT

   Part

     id="007"

   Part

     id= "007"

   Part

     id= "007"

在ognl语言参考中没有找到。

尝试自己扩展一个吧。