spring in action 4th --- quick start

悠悠 2022-07-16 07:43 63阅读 0赞

读spring in action.

1.   环境搭建
2.  quick-start依赖注入
3.  面向切面

# 1.环境搭建 #

*  jdk1.8
 *  gradle 2.12
 *  Intelij idea 2016.2.1

![686418-20160815164334171-1136599345.png][]

## 1.1创建一个gradle项目 ##

在idea中，new -> project -> gradle 创建一个空项目。创建成功后修改build.gradle ：

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group 'com.test'
    version '1.0-SNAPSHOT'
    
    apply plugin: 'java'
    apply plugin: 'war'
    
    sourceCompatibility = 1.8
    targetCompatibility = 1.8
    
    repositories {
        mavenLocal()
        mavenCentral()
    }
    
    dependencies {
        testCompile group: 'junit', name: 'junit', version: '4.11'
        
    }

根目录下创建.gitignore：

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# Created by .ignore support plugin (hsz.mobi)
    .idea/
    .gradle/
    build/
    out/
    */build/

## 1.2 quick start ##

spring的核心是依赖注入，那么简单的做一个入门测试。

在项目名上右键，new->module->gradle->创建一个java项目quick-start. 修改生产的build.gradle:

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group 'com.test'
    version '1.0-SNAPSHOT'
    
    apply plugin: 'java'
    
    sourceCompatibility = 1.8
    
    repositories {
        mavenLocal()
        mavenCentral()
    }
    
    dependencies {
        testCompile group: 'junit', name: 'junit', version: '4.11'
    
        compile 'org.springframework:spring-context:4.3.2.RELEASE'
    }

这里参考：[http://projects.spring.io/spring-framework/\#quick-start][http_projects.spring.io_spring-framework_quick-start] 的案例.

在quick-start module下创建一个package src/main/java，在java文件夹上右键，Mark Directory as -> Sources Root.

这时候idea的项目配置还没有刷新，需要手动点击一下刷新：

![686418-20160815164653218-1836713124.png][]

这时候，idea就可以resolve quick-start这个项目以及他的dependency了。

添加spring-context会添加其他依赖：

dependencies {
        compile 'org.springframework:spring-context:4.3.2.RELEASE'
    }

![686418-20160815170942515-1552437993.png][]

### 1.2.1 Hello World ###

我们来创建打印消息的组件。MessagePrinter打印一个MessageService的实例的信息。：

![686418-20160815171248453-1695599305.png][]

创建接口com.test.hello.MessageService:

package com.test.hello;
    
    /**
     * Created by rmiao on 8/15/2016.
     */
    public interface MessageService {
        String getMessage();
    }

创建组件com.test.hello.MessagePrinter：

package com.test.hello;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    
    /**
     * Created by rmiao on 8/15/2016.
     */
    @Component
    public class MessagePrinter {
    
        final private MessageService service;
    
        @Autowired
        public MessagePrinter(MessageService service){
            this.service = service;
        }
    
        public void printMessage(){
            System.out.println(this.service.getMessage());
        }
    }

@Component声明MessagePrinter是一个bean，由spring容器来管理。

@Autowired 这里是构造器注入，会根据构造器参数的类型和参数名来将spring容器中的bean注入构造器。

针对MessagePrinter的注入参数，我们需要一个MessageService的实现：

MessageService mockMessageService(){
            return () -> "Hello World!";
    }

下面开始启动spring容器来测试这个打印消息组件：

创建com.test.hello.Application：

package com.test.hello;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.annotation.AnnotationConfigApplicationContext;
    import org.springframework.context.annotation.Bean;
    import org.springframework.context.annotation.ComponentScan;
    import org.springframework.context.annotation.Configuration;
    
    /**
     * Created by rmiao on 8/15/2016.
     */
    @Configuration
    @ComponentScan
    public class Application {
    
        @Bean
        MessageService mockMessageService(){
            return () -> "Hello World!";
        }
    
        public static void main(String[] args){
            ApplicationContext context = new AnnotationConfigApplicationContext(Application.class);
            MessagePrinter printer = context.getBean(MessagePrinter.class);
            printer.printMessage();
        }
    }

@Configuration来声明Application是一个配置类，相当于xml配置文件。这里只配置了一个bean mockMessageService.

@Bean 用来声明一个bean并交由spring容器管理。相当于xml配置文件中<bean>. 这种方式表示声明一个MessageService的类的bean，bean id为mockMessageService。

@ComponentScan来声明spring容器扫描范围，这种方式表示扫描Application所在包以及子包下的所有类，然后将识别到的bean放到spring容器中。

AnnotationConfigApplicationContext用来创建spring容器。getBean来获取容器中的bean。

最终，打印Hello World!

### 1.2.2 Aop面向切面 ###

spring的另一个强大特性是面向切面编程。可以在任意方法的调用前后进行一些操作。比如记录日志:

添加aop依赖：

dependencies {
    
        compile group: 'org.springframework', name: 'spring-aop', version: '4.3.2.RELEASE'
        compile group: 'org.aspectj', name: 'aspectjweaver', version: '1.8.9'
    
    }

添加logback日志组件依赖：

dependencies {
    
        compile group: 'org.slf4j', name: 'slf4j-api', version: '1.7.21'
        compile group: 'ch.qos.logback', name: 'logback-classic', version: '1.1.7'
        compile group: 'ch.qos.logback', name: 'logback-core', version: '1.1.7'
        compile group: 'org.codehaus.groovy', name: 'groovy', version: '2.4.7'
    
    }

在src/main/resources下创建logback.groovy：

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import ch.qos.logback.classic.encoder.PatternLayoutEncoder
    import ch.qos.logback.core.ConsoleAppender
    import ch.qos.logback.core.rolling.FixedWindowRollingPolicy
    import ch.qos.logback.core.rolling.RollingFileAppender
    import ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy
    
    import static ch.qos.logback.classic.Level.DEBUG
    import static ch.qos.logback.classic.Level.INFO
    
    appender("STDOUT", ConsoleAppender) {
        encoder(PatternLayoutEncoder) {
            pattern = "%d{HH:mm:ss.SSS} [%thread] %-5level %logger{5}  - %msg%n"
        }
    }
    appender("FILE", RollingFileAppender){
        file = "quick-start/log/project.log"
        encoder(PatternLayoutEncoder) {
            pattern = "%d{yyyy-MM-dd_HH:mm:ss.SSS} [%thread] %-5level %logger{36} - %msg%n"
        }
        rollingPolicy(FixedWindowRollingPolicy) {
            fileNamePattern = "quick-start/log/project.%i.log.zip"
            minIndex = 1
            maxIndex = 10
        }
        triggeringPolicy(SizeBasedTriggeringPolicy) {
            maxFileSize = "2MB"
        }
    }
    
    // specify  level
    logger("com.test.hello", DEBUG)
    //By default, the level of the root level is set to DEBUG
    root(DEBUG, ["STDOUT"])

下面开始面相切面编程。

我们想要在消息打印组件的前后做一些工作，但又不想要修改打印组件的内容。那么可以使用@Aspect：

创建：com.test.hello.Monitor.java:

package com.test.hello;
    
    import org.aspectj.lang.annotation.After;
    import org.aspectj.lang.annotation.Aspect;
    import org.aspectj.lang.annotation.Before;
    import org.aspectj.lang.annotation.Pointcut;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import org.springframework.stereotype.Component;
    
    /**
     * Created by rmiao on 8/15/2016.
     */
    @Aspect
    @Component
    public class Monitor {
    
        private final Logger logger = LoggerFactory.getLogger(Monitor.class);
    
        @Pointcut("execution(* com.test.hello.MessagePrinter.printMessage())")
        public void  message(){}
    
        @Before(value = "message()")
        public void pre(){
            logger.info("before print.");
        }
    
        @After(value = "message()")
        public void after(){
            logger.info("after print.");
        }
    
    
    }

@Aspect表示这是一个aop切面。等价于xml配置中的<aop>

@Pointcut表示切面的匹配方式

@Before表示切面调用前执行

@After表示切面调用后执行。

要使上述的配置生效，还需开启切面,在配置类中声明@EnableAspectJAutoProxy：

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package com.test.hello;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.annotation.*;
    
    /**
     * Created by rmiao on 8/15/2016.
     */
    @Configuration
    @ComponentScan
    @EnableAspectJAutoProxy
    public class Application {
    
        @Bean
        MessageService mockMessageService(){
            return () -> "Hello World!";
        }
    
        public static void main(String[] args){
            ApplicationContext context = new AnnotationConfigApplicationContext(Application.class);
            MessagePrinter printer = context.getBean(MessagePrinter.class);
            printer.printMessage();
        }
    }

运行：

八月 15, 2016 9:13:45 下午 org.springframework.context.annotation.AnnotationConfigApplicationContext prepareRefresh
    信息: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@31cefde0: startup date [Mon Aug 15 21:13:45 CST 2016]; root of context hierarchy
    21:13:49.278 [main] INFO  c.t.h.Monitor  - before print.
    Hello World!
    21:13:49.306 [main] INFO  c.t.h.Monitor  - after print.

[686418-20160815164334171-1136599345.png]: /images/20220716/49c62a76320b43628d64292a0b2c332e.png
[ContractedBlock.gif]: http://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif
[ExpandedBlockStart.gif]: /images/20220716/f555781dd8ff4c51837dda6de6ec7101.png
[http_projects.spring.io_spring-framework_quick-start]: http://projects.spring.io/spring-framework/#quick-start
[686418-20160815164653218-1836713124.png]: /images/20220716/985d34c1dd304f2a8dffc0d2a2a5352a.png
[686418-20160815170942515-1552437993.png]: /images/20220716/8ee68dd8ee6a4ff3b381048625e62a0d.png
[686418-20160815171248453-1695599305.png]: /images/20220716/e7a2e21d981b4c06b619c0f98937d023.png