spring之SpEL表达式详解

<dependencies>
		<dependency>
			<groupId>junit</groupId>
			<artifactId>junit</artifactId>
			<version>4.11</version>
			<scope>test</scope>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-core</artifactId>
			<version>4.0.5.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-expression</artifactId>
			<version>4.0.5.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
			<version>4.0.5.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-beans</artifactId>
			<version>4.0.5.RELEASE</version>
		</dependency>
</dependencies>

<bean id="MyMessage" class="cn.spy.spel.injection.MyMessage">
        <property name="message" value="#{systemProperties['user.language']}"></property>
</bean>

public class MyMessage {
 
	private String message;
 
	public String getMessage() {
		return message;
	}
 
	public void setMessage(String message) {
		this.message = message;
	}
	
}

public class Test {
	public static void main(String[] args) {
		ApplicationContext context =new ClassPathXmlApplicationContext("applicationContext.xml");
		MyMessage myMessage =context.getBean(MyMessage.class);
		System.out.println(myMessage.getMessage());
	}
}

<context:component-scan base-package="cn.spy.spel"></context:component-scan>

@Component
public class MyMessage2 {
	
	@Value("#{systemProperties['user.language']}")
	private String message;
 
	public String getMessage() {
		return message;
	}
}

public static void main(String[] args) {
		ApplicationContext context =new ClassPathXmlApplicationContext("applicationContext.xml");
		MyMessage2 myMessage =context.getBean(MyMessage2.class);
		System.out.println(myMessage.getMessage());
	}

ExpressionParser parser =new SpelExpressionParser();

public class HelloWorldTest {
	ExpressionParser parser;
	
	@Before
	public void setup(){
		//初始化创建SpEL表达式解析器
		parser =new SpelExpressionParser();
	}
	
	@Test
	public void test(){
		//使用解析器解析出表达式exp
		Expression exp=parser.parseExpression("'Hello World'");
		//在表达式中获取指定类型的值
		String value =exp.getValue(String.class);
		assertThat(value ,is("Hello World"));
	}
}

public class User {
	
	private String username;
	private String passWord;
	public void setUsername(String username) {
		this.username = username;
	}
	public void setPassword(String password) {
		this.password = password;
	}
	public String getUsername() {
		return "李四";
	}
	public String getPassword() {
		return "lisi123";
	}
	public void printUser(){
		System.out.println("当前用户的用户名："+username+" ,密码："+password);
	}
}

        <bean id="user1" class="cn.spy.spel.method.User">
			<property name="username" value="张三"></property>
			<property name="password" value="zhangsan123"></property>
		</bean>		
				
		<bean id="user2" class="cn.spy.spel.method.User">
			<property name="username" value="#{user2.getUsername()}"></property>
			<property name="password" value="#{user2.getPassword()}"></property>
		</bean>	

public class TestMethod {
	public static void main(String[] args) {
		ApplicationContext context =new ClassPathXmlApplicationContext("applicationContext.xml");
		User user1 =(User) context.getBean("user1");
		user1.printUser();
		User user2 =(User) context.getBean("user2");
		user2.printUser();
	}
}

@Test
public void test(){
	ExpressionParser parser =new SpelExpressionParser();
	Expression exp=parser.parseExpression("new Double(3.1415926)");
	Double value =exp.getValue(Double.class);
	assertThat(value ,is(3.1415926));
}

@Test
public void test(){
	ExpressionParser parser =new SpelExpressionParser();
	Expression exp=parser.parseExpression("T(java.lang.Math).abs(-1)");
	Integer value =exp.getValue(Integer.class);
	assertThat(value ,is(1));
}

public class TestSpEL {
	@Test
	public void test(){
		ExpressionParser parser =new SpelExpressionParser();
		StandardEvaluationContext context =new StandardEvaluationContext();
		context.setVariable("message", "Hello World");
		String value =parser.parseExpression("#message").getValue(context, String.class);
		assertThat(value, is("Hello World"));
	}
}

public class TestSpEL {
	@Test
	public void test(){
		ExpressionParser parser =new SpelExpressionParser();
		StandardEvaluationContext context =new StandardEvaluationContext();
		context.setRootObject(new Var());
		Assert.assertTrue(parser.parseExpression("#root").getValue(context) instanceof Var);
	}
}

parser.parseExpression("@systemProperties['java.version']").getValue(context);
parser.parseExpression("@systemProperties[JAVA_HOME]").getValue(context);

@Test
	public void test(){
		ExpressionParser parser =new SpelExpressionParser();
		assertThat(parser.parseExpression("35 matches '[0-9]+'").getValue(Boolean.class), is(true));
	}

@Test
public void test(){
	ExpressionParser parser =new SpelExpressionParser();
	assertThat(parser.parseExpression("3 between {2,5}").getValue(Boolean.class), is(true));
}