SpEL 参考

官方参考

特性概览

• 字符表达式
• 布尔和关系操作符
• 正则表达式
• 类表达式
• 访问properties，arrays，lists，maps
• 方法调用
• 赋值
• 调用构造器
• 三元操作符
• 变量
• 用户自定义函数
• 集合投影
• 集合选择
• 内联列表
• 模板表达式

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
字符表达式：

@Test
public void test01() {	// 字符串表达式
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("new String('Hello, World').concat('!')");
	System.out.println(exp.getValue());
}

@Test
public void test02() {	// 字符串表达式
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("'HelloWorld'.bytes.length");  
	int length= (Integer) exp.getValue();
	System.out.println(length);
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
布尔和关系表达式：

@Test
public void test03() {	// 布尔和关系表达式
	ExpressionParser parser = new SpelExpressionParser();
	EvaluationContext context = new StandardEvaluationContext(new java.util.Date());
	Expression exp = parser.parseExpression("#root.year + 1900 eq 2011");
	boolean flag = exp.getValue(context, Boolean.class);
	System.out.println(flag);
}

@Test
public void test04() {	// 布尔和关系表达式
	ExpressionParser parser = new SpelExpressionParser();
	EvaluationContext context = new StandardEvaluationContext(new java.util.Date());
	Expression exp = parser.parseExpression("!(#root.year + 1900 == 2011)");
	boolean flag = exp.getValue(context, Boolean.class);
	System.out.println(flag);
}

关系表达式语言中可以使用符号： ==, >=, <=, !, >, <
也可以使用eq, ge, le, not, gt, lt
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
正则表达式：

@Test
public void test05() {	// 正则表达式
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("'138-8000-4000' matches '\\d{3}-\\d{4}-\\d{4}'");
	boolean flag = exp.getValue(Boolean.class);
	System.out.println(flag);
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
类表达式：

@Test
public void test06() {	// 类表达式
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("T(java.util.UUID).randomUUID().toString().toUpperCase()");
	String uuid = exp.getValue(String.class);
	System.out.println(uuid);
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
访问properties，arrays，lists，maps：

@Test
public void test07() {	// 访问arrays
	String[] array = new String[] {"马勒", "格", "彼得"};
	StandardEvaluationContext context = new StandardEvaluationContext();
	context.setVariable("array", array);
	
	ExpressionParser parser = new SpelExpressionParser();
	String value = parser.parseExpression("#array[0]").getValue(context, String.class);
	System.out.println(value);
}

@Test
public void test08() {	// 访问list
	List<String> list = new ArrayList<String>(3);
	list.add("马勒");
	list.add("格");
	list.add("彼得");
	StandardEvaluationContext context = new StandardEvaluationContext();
	context.setVariable("list", list);
	ExpressionParser parser = new SpelExpressionParser();
	String value = parser.parseExpression("#list[1]").getValue(context, String.class);
	System.out.println(value);
}

@Test
public void test09() {	// 访问map
	Map<String, String> map = new HashMap<String, String>();
	map.put("first-name", "马勒");
	map.put("middle-name", "格");
	map.put("last-name", "彼得");
	StandardEvaluationContext context = new StandardEvaluationContext();
	context.setVariable("map", map);
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("#map['last-name']");
	String value = exp.getValue(context, String.class);
	System.out.println(value);
}

@Test
public void test09_2() {	// 访问Properties
	ExpressionParser parser = new SpelExpressionParser();
	EvaluationContext context = new StandardEvaluationContext(System.getProperties());
	Expression exp = parser.parseExpression("#root['user.dir']");		
	String userDir = exp.getValue(context, String.class);
	System.out.println("user dir :" + userDir);
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
方法调用：

@Test
public void test10() {	// 方法调用
	// 静态方法和非静态方法都可以用
	String el = "T(java.util.Calendar).getInstance().getTimeInMillis()";
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression(el);
	String str = exp.getValue(String.class);
	System.out.println(str);
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
赋值表达式：

@Test
public void test11() {	// 赋值
	List<String> list = new ArrayList<String>();
	list.add("");
	list.add("");
	list.add("");
	StandardEvaluationContext context = new StandardEvaluationContext(list);
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("#root[2] = '123'");
	String result = (String)exp.getValue(context);
	
	System.out.println(result);
	System.out.println(list.get(2));
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
三元表达式：

@Test
public void test14() {	// 三元操作符
	ExpressionParser parser = new SpelExpressionParser();
	String result = parser.parseExpression("true?'love':'hate'").getValue(String.class);
	System.out.println(result);
}

@Test
public void test15() {	// 三元操作符
	ExpressionParser parser = new SpelExpressionParser();
	String name = parser.parseExpression("null?:'Unknown'").getValue(String.class);
	System.out.println(name); // 'Unknown'
}

@Test
public void test16() {	// 三元操作符
	class User {
		public String name;
	};
	EvaluationContext context = new StandardEvaluationContext(new User());
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("#root.name?.length()");
	Integer length = exp.getValue(context, Integer.class);
	System.out.println(length);
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
使用变量：

@Test
public void test17() {	// 变量
	class User {
		public String name;
	};
	User u = null;
	StandardEvaluationContext context = new StandardEvaluationContext();
	context.setVariable("user", u = new User());
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("#user.name = 'Malege Peter'");
	String name = exp.getValue(context, String.class);
	System.out.println(name);
	System.out.println(u.name);
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
用户自定义函数：

@Test
public void test18() throws SecurityException, NoSuchMethodException {	// 用户自定义函数
	class StringUtil {
		public String reverse(CharSequence s) {
			StringBuffer buffer = new StringBuffer(s);
			return buffer.reverse().toString();
		}
	};
	
	StandardEvaluationContext context = new StandardEvaluationContext(new StringUtil());
	context.registerFunction("reverse", StringUtil.class.getDeclaredMethod("reverse", new Class<?>[]{CharSequence.class}));
	
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("reverse('Hello, World.')");
	String str = exp.getValue(context, String.class);
	System.out.println(str);
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
集合的选择：

@Test
public void test19() {	// 集合选择
	int[] primes = {1,3,5,7,11,13,17,19,23};
	EvaluationContext context = new StandardEvaluationContext(primes);
	
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("#root.?[#this le 11]");
	List<Integer> list = exp.getValue(context, List.class);
	System.out.println(list);
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
集合的投影：

@Test
public void test20() {	// 集合投影
	class User {
		public String name;
		public String password;
		public User(String n, String p) {
			name = n; password = p;
		}
	};
	
	Map<Integer, User> map = new HashMap<Integer, User>();
	map.put(1, new User("zhang san", "1234"));
	map.put(2, new User("li si", "12345"));
	map.put(3, new User("wang wu", "****"));
	
	StandardEvaluationContext context = new StandardEvaluationContext();
	context.setVariable("map", map);
	
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("#map.![value.name]");
	List<String> list = exp.getValue(context, List.class);
	System.out.println(list);
}

------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
内联列表：

@Test
@Test
public void test21() {	// 内联列表
	ExpressionParser parser = new SpelExpressionParser();
	Expression exp = parser.parseExpression("{{1,2,3,4}, {5,6,7,8}}");
	List<List<Integer> > list = exp.getValue(List.class);
	
	for (List<Integer> is : list) {
		System.out.println(is);
	}
}