Spring4中的@Value的使用(学习笔记)

1、@Value用途介绍

Spring主要在注解@Value的参数中使用表达式

@Value的使用主要有以下几种情况

（1）注入普通字符

（2）注入操作系统属性

（3）注入表达式运算结果

（4）注入其他Bean的属性

（5）注入文件内容

（6）注入网址内容

（7）注入属性文件

2、案例编写之项目目录结构

3、pom.xml文件内容

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>com.wisely</groupId>
    <artifactId>highlight_spring4</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <properties>
        <java.version>1.8</java.version>
        <spring-framework.version>4.1.5.RELEASE</spring-framework.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-context</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>
        <!-- spring aop支持 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-aop</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>
        <!-- aspectj支持 -->
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjrt</artifactId>
            <version>1.8.6</version>
        </dependency>
        <dependency>
            <groupId>org.aspectj</groupId>
            <artifactId>aspectjweaver</artifactId>
            <version>1.8.5</version>
        </dependency>

        <!-- Spring test 支持 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>
        <dependency>
            <groupId>junit</groupId>
            <artifactId>junit</artifactId>
            <version>4.11</version>
        </dependency>
        <dependency>
            <groupId>commons-io</groupId>
            <artifactId>commons-io</artifactId>
            <version>2.3</version>
        </dependency>

        <dependency>
            <groupId>javax.annotation</groupId>
            <artifactId>jsr250-api</artifactId>
            <version>1.0</version>
        </dependency>

        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-test</artifactId>
            <version>${spring-framework.version}</version>
        </dependency>
    </dependencies>
    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>2.3.2</version>
                <configuration>
                    <source>${java.version}</source>
                    <target>${java.version}</target>
                </configuration>
            </plugin>
        </plugins>
    </build>

</project>
           

4、test.txt的内容

测试文件
           

5、test.properties的内容

book.author=wangyunfei
book.name=spring boot
           

6、DemoService的内容

package com.wisely.highlight_spring4.ch2.el;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Service;

@Service
public class DemoService {
    @Value("其它类的属性")
    private String another;

    public String getAnother() {
        return another;
    }

    public void setAnother(String another) {
        this.another = another;
    }
}
           

7、ElConfig的内容

package com.wisely.highlight_spring4.ch2.el;

import org.apache.commons.io.IOUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.context.annotation.PropertySource;
import org.springframework.context.support.PropertySourcesPlaceholderConfigurer;
import org.springframework.core.env.Environment;
import org.springframework.core.io.Resource;

@Configuration
@ComponentScan("com.wisely.highlight_spring4.ch2.el")
@PropertySource("classpath:test.properties")
public class ElConfig {

    @Value("I Love You!") //
    private String normal;

    @Value("#{systemProperties['os.name']}") //
    private String osName;

    @Value("#{ T(java.lang.Math).random() * 100.0 }") //
    private double randomNumber;

    @Value("#{demoService.another}") //
    private String fromAnother;

    @Value("classpath:test.txt") //
    private Resource testFile;

    @Value("http://www.baidu.com") //
    private Resource testUrl;

    @Value("${book.name}") //
    private String bookName;

    @Autowired
    private Environment environment; //7

    @Bean //
    public static PropertySourcesPlaceholderConfigurer propertyConfigure() {
        return new PropertySourcesPlaceholderConfigurer();
    }

    public void outputResource() {
        try {
            System.out.println(normal);
            System.out.println(osName);
            System.out.println(randomNumber);
            System.out.println(fromAnother);

            System.out.println(IOUtils.toString(testFile.getInputStream()));
            System.out.println(IOUtils.toString(testUrl.getInputStream()));
            System.out.println(bookName);
            System.out.println(environment.getProperty("book.author"));
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
           

8、Main的内容

package com.wisely.highlight_spring4.ch2.el;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

public class Main {

    public static void main(String[] args) {
        AnnotationConfigApplicationContext context =
                new AnnotationConfigApplicationContext(ElConfig.class);

        ElConfig resourceService = context.getBean(ElConfig.class);

        resourceService.outputResource();
        context.close();
    }
}
           

9、最终运行的结果