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Springboot自动装配实现过程代码实例

2020年06月23日  | 移动技术网IT编程  | 我要评论

创建一个简单的项目：

<?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>

  <parent>
    <artifactid>spring-boot-starter-parent</artifactid>
    <groupid>org.springframework.boot</groupid>
    <version>2.1.12.release</version>
  </parent>

  <groupid>com.xiazhi</groupid>
  <artifactid>demo</artifactid>
  <version>1.0-snapshot</version>

  <dependencies>
    <dependency>
      <groupid>org.springframework.boot</groupid>
      <artifactid>spring-boot-starter-web</artifactid>
    </dependency>
    <dependency>
      <groupid>org.springframework.boot</groupid>
      <artifactid>spring-boot-starter-test</artifactid>
    </dependency>
  </dependencies>
</project>

首先创建自定义注解：

package com.xiazhi.demo.annotation;

import java.lang.annotation.elementtype;
import java.lang.annotation.retention;
import java.lang.annotation.retentionpolicy;
import java.lang.annotation.target;

/**
 * mycomponent 作用于类上，表示这是一个组件，于component，service注解作用相同
 * @author zhaoshuai
 */
@target(elementtype.type)
@retention(retentionpolicy.runtime)
public @interface mycomponent {

}
package com.xiazhi.demo.annotation;

import java.lang.annotation.elementtype;
import java.lang.annotation.retention;
import java.lang.annotation.retentionpolicy;
import java.lang.annotation.target;

/**
 * 作用于字段上，自动装配的注解，与autowired注解作用相同
 * @author zhaoshuai
 */
@target(elementtype.field)
@retention(retentionpolicy.runtime)
public @interface reference {
}

然后写配置类：

package com.xiazhi.demo.config;

import com.xiazhi.demo.annotation.mycomponent;

import org.springframework.beans.factory.support.beandefinitionregistry;
import org.springframework.context.resourceloaderaware;
import org.springframework.context.annotation.classpathbeandefinitionscanner;
import org.springframework.context.annotation.importbeandefinitionregistrar;
import org.springframework.core.io.resourceloader;
import org.springframework.core.type.annotationmetadata;
import org.springframework.core.type.filter.annotationtypefilter;


/**
 * @author zhaoshuai
 * @company lihfinance.com
 * @date create in 2020/3/21
 **/
public class componentautoconfiguration implements importbeandefinitionregistrar, resourceloaderaware {

  private resourceloader resourceloader;

  @override
  public void registerbeandefinitions(annotationmetadata annotationmetadata, beandefinitionregistry beandefinitionregistry) {
    string classname = annotationmetadata.getclassname();
    string basepackages = classname.substring(0, classname.lastindexof("."));

    classpathbeandefinitionscanner scanner = new classpathbeandefinitionscanner(beandefinitionregistry, false);
    scanner.addincludefilter(new annotationtypefilter(mycomponent.class));
    scanner.scan(basepackages);
    scanner.setresourceloader(resourceloader);
  }

  @override
  public void setresourceloader(resourceloader resourceloader) {
    this.resourceloader = resourceloader;
  }

}

上面是配置扫描指定包下被mycomponent注解标注的类并注册为spring的bean，bean注册成功后，下面就是属性的注入了

package com.xiazhi.demo.config;

import com.xiazhi.demo.annotation.mycomponent;
import com.xiazhi.demo.annotation.reference;
import org.springframework.beans.beansexception;
import org.springframework.beans.factory.config.beanpostprocessor;
import org.springframework.boot.springbootconfiguration;
import org.springframework.context.applicationcontext;
import org.springframework.context.applicationcontextaware;
import org.springframework.context.annotation.bean;
import org.springframework.util.reflectionutils;

import java.lang.reflect.field;

/**
 * @author zhaoshuai
 * @company lihfinance.com
 * @date create in 2020/3/21
 **/
@springbootconfiguration
public class configuration implements applicationcontextaware {
  private applicationcontext applicationcontext;

  @bean
  public beanpostprocessor beanpostprocessor() {
    return new beanpostprocessor() {

      /**
       * @company lihfinance.com
       * @author create by zhaoshuai in 2020/3/21
       * 在bean注册前会被调用
       * @param [bean, beanname]
       * @return java.lang.object
       **/
      @override
      public object postprocessbeforeinitialization(object bean, string beanname) throws beansexception {
        return bean;
      }

      /**
       * @company lihfinance.com
       * @author create by zhaoshuai in 2020/3/21
       * 在bean注册后会被加载，本次在bean注册成功后注入属性值
       * @param [bean, beanname]
       * @return java.lang.object
       **/
      @override
      public object postprocessafterinitialization(object bean, string beanname) throws beansexception {
        class<?> clazz = bean.getclass();
        if (!clazz.isannotationpresent(mycomponent.class)) {
          return bean;
        }

        field[] fields = clazz.getdeclaredfields();
        for (field field : fields) {
          if (!field.isannotationpresent(reference.class)) {
            continue;
          }
          class<?> type = field.gettype();
          object obj = applicationcontext.getbean(type);
          reflectionutils.makeaccessible(field);
          reflectionutils.setfield(field, bean, obj);
        }
        return bean;
      }
    };
  }

  @override
  public void setapplicationcontext(applicationcontext applicationcontext) throws beansexception {
    this.applicationcontext = applicationcontext;
  }
}

下面开始使用注解来看看效果：

package com.xiazhi.demo.service;

import com.xiazhi.demo.annotation.mycomponent;

import javax.annotation.postconstruct;

/**
 * @author zhaoshuai
 * @company lihfinance.com
 * @date create in 2020/3/21
 **/
@mycomponent
public class myservice {

  @postconstruct
  public void init() {
    system.out.println("hello world");
  }

  public void test() {
    system.out.println("测试案例");
  }
}
package com.xiazhi.demo.service;

import com.xiazhi.demo.annotation.mycomponent;
import com.xiazhi.demo.annotation.reference;

/**
 * @author zhaoshuai
 * @company lihfinance.com
 * @date create in 2020/3/21
 **/
@mycomponent
public class myconsumer {

  @reference
  private myservice myservice;

  public void aaa() {
    myservice.test();
  }
}

启动类要引入配置文件：

import注解引入配置文件。

编写测试类测试：

@springboottest(classes = applicationrun.class)
@runwith(springrunner.class)
public class testdemo {

  @autowired
  public myconsumer myconsumer;

  @test
  public void fun1() {
    myconsumer.aaa();
  }
}

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