SpringBoot动态注入及操作Bean

写在前面：2020年面试必备的Java后端进阶面试题总结了一份复习指南在Github上，内容详细，图文并茂，有需要学习的朋友可以Star一下！
GitHub地址：https://github.com/abel-max/Java-Study-Note/tree/master

在Spring中我们通过getBean来获得对象,但这些对象都是事先定义好的,如果需要操作事先未定义的Bean就需要动态注入、修改和删除Bean

思路
在Spring中，BeanFactory负责管理Bean，具体来说是DefaultListableBeanFactory，我们只需要获取到当前上下文中的BeanFactory，就能执行其中的注册Bean的方法registerBeanDefinition，注册Bean时需要Bean的信息，Spring提供了BeanDefinitionBuilder.genericBeanDefinition()方法来构建BeanDefinition，用这些方法就可以实现Bean的动态注入

代码实现
测试服务类TestService
创建一个测试类来测试Bean的操作，这个类上没有加注解，Spring在加载时不会自动注入

package com.mantis.bean.service;
/**
 * @Description:
 * @author: wei.wang
 * @since: 2020/9/17 12:53
 * @history: 1.2020/9/17 created by wei.wang
 */
public class TestService {
    private String name;
    private String id;
    public String getId() {
        return id;
    }    public void setId(String id) {
        this.id = id;
    }    public String getName() {
        return name;
    }    public void setName(String name) {
        this.name = name;
    }    public void print() {
        System.out.println("获取bean,name=" + name + ",id=" + id);
    }    @Override
    public String toString() {
        return "TestService{" +
                "name='" + name + '\'' +
                ", id='" + id + '\'' +
                '}';
    }}

SpringContextUtil类
操作Bean的Util类，其中上线文ApplicationContext在SpringBoot启动时设置，也可以直接使用Autowired注入或者根据具体项目具体实现

package com.mantis.bean.util;
import org.springframework.beans.factory.NoSuchBeanDefinitionException;
import org.springframework.context.ApplicationContext;
/**
 * @Description:
 * @author: wei.wang
 * @since: 2020/9/17 12:52
 * @history: 1.2020/9/17 created by wei.wang
 */
public class SpringContextUtil {
    private static ApplicationContext applicationContext;
    //获取上下文
    public static ApplicationContext getApplicationContext() {
        return applicationContext;
    }
    //设置上下文
    public static void setApplicationContext(ApplicationContext applicationContext) {
        SpringContextUtil.applicationContext = applicationContext;
    }
    //通过名字获取上下文中的bean
    public static Object getBean(String name) {
        try {
            return applicationContext.getBean(name);
        } catch (NoSuchBeanDefinitionException ex) {
            return null;
        }
    }
    //通过类型获取上下文中的bean
    public static Object getBean(Class<?> requiredType) {
        return applicationContext.getBean(requiredType);
    }
}

启动类SpringBootBeanApplication
在启动类上设置上下文

package com.mantis.bean;
import com.mantis.bean.util.SpringContextUtil;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ApplicationContext;
@SpringBootApplication
public class SpringBootBeanApplication {
    public static void main(String[] args) {
        ApplicationContext app = SpringApplication.run(SpringBootBeanApplication.class, args);
        SpringContextUtil.setApplicationContext(app);    }}
注入Bean
向Spring上下文中注入Bean，注入前先检查Bean是否已经存在

/**
     * 注册Bean     *     * @return
     */    @GetMapping("/bean/register/{beanName}")
    public String registerBean(@PathVariable String beanName) {        //获取context        ConfigurableApplicationContext configurableApplicationContext = (ConfigurableApplicationContext) SpringContextUtil.getApplicationContext();        //获取BeanFactory        DefaultListableBeanFactory defaultListableBeanFactory = (DefaultListableBeanFactory) configurableApplicationContext.getBeanFactory();        //创建bean信息.        BeanDefinitionBuilder beanDefinitionBuilder = BeanDefinitionBuilder.genericBeanDefinition(TestService.class);        beanDefinitionBuilder.addPropertyValue("id", "1");
        beanDefinitionBuilder.addPropertyValue("name", "张三");
        //判断Bean是否已经注册        Object beanObject = SpringContextUtil.getBean(beanName);        if (beanObject != null) {
            System.out.println(String.format("Bean %s 已注册", beanName));
        } else {
            //动态注册bean.            defaultListableBeanFactory.registerBeanDefinition(beanName, beanDefinitionBuilder.getBeanDefinition());            //获取动态注册的bean.            beanObject = SpringContextUtil.getBean(beanName);            if (beanObject != null) {
                System.out.println(String.format("Bean %s 注册成功", beanName));
                return beanObject.toString();
            } else {
                return "register Bean Error";
            }        }        return "register Bean Success";
    }

修改Bean
从SpringContext中获取到指定Bean的Class对象，获取到之后就可以根据字段进行赋值

/**
     * 动态修改Bean     *     * @return
     */    @GetMapping("/bean/update/{beanName}")
    public String update(@PathVariable String beanName) {        ApplicationContext applicationContext = SpringContextUtil.getApplicationContext();        String[] beans = applicationContext.getBeanDefinitionNames();        for (String bean : beans) {
            // 拿到bean的Class对象            Class<?> beanType = applicationContext.getType(bean);            if (beanType == null) {
                continue;            }            // 拿到当前bean类型的所有字段            Field[] declaredFields = beanType.getDeclaredFields();            if (beanName.equals(bean)) {
                for (Field field : declaredFields) {
                    // 从spring容器中拿到这个具体的bean对象                    Object beanObject = applicationContext.getBean(bean);                    // 当前字段设置新的值                    try {                        String fieldName = field.getName();                        if ("name".equals(fieldName)) {
                            setFieldData(field, beanObject, "AL113A5");
                        } else if ("id".equals(fieldName)) {
                            setFieldData(field, beanObject, "12");
                        }                    } catch (Exception e) {                        e.printStackTrace();                    }                }            }        }        return "update Bean Success";
    }    private void setFieldData(Field field, Object bean, String data) throws Exception {        field.setAccessible(true);
        Class<?> type = field.getType();
        if (type.equals(String.class)) {
            field.set(bean, data);        } else if (type.equals(Integer.class)) {
            field.set(bean, Integer.valueOf(data));        } else if (type.equals(Long.class)) {
            field.set(bean, Long.valueOf(data));        } else if (type.equals(Double.class)) {
            field.set(bean, Double.valueOf(data));        } else if (type.equals(Short.class)) {
            field.set(bean, Short.valueOf(data));        } else if (type.equals(Byte.class)) {
            field.set(bean, Byte.valueOf(data));        } else if (type.equals(Boolean.class)) {
            field.set(bean, Boolean.valueOf(data));        } else if (type.equals(Date.class)) {
            field.set(bean, new Date(Long.parseLong(data)));        }    }

移除Bean
将Bean从Spring上下文中移除

/**
     * 移除Bean
     *
     * @return
     */
    @GetMapping("/bean/remove/{beanName}")
    public String removeBeanDefinition(@PathVariable String beanName) {
        Object beanObject = SpringContextUtil.getBean(beanName);
        if (beanObject == null) {
            System.out.println(String.format("Bean %s 不存在", beanName));
            return "remove Error";
        }        //获取context.
        ConfigurableApplicationContext configurableApplicationContext = (ConfigurableApplicationContext) SpringContextUtil.getApplicationContext();
        //获取BeanFactory
        DefaultListableBeanFactory defaultListableBeanFactory = (DefaultListableBeanFactory) configurableApplicationContext.getBeanFactory();
        defaultListableBeanFactory.removeBeanDefinition(beanName);
        System.out.println(String.format("Bean %s 已移除", beanName));
        return "remove Success";
    }

测试
写一个操作Bean的方法

/**
     * 操作Bean
     *
     * @return
     */
    @GetMapping("/bean/print/{beanName}")
    public String print(@PathVariable String beanName) {
        Object beanObject = SpringContextUtil.getBean(beanName);
        if (beanObject != null) {
            ((TestService) beanObject).print();            return beanObject.toString();
        } else {
            System.out.println(String.format("Bean %s 不存在", beanName));
        }        return String.format("Bean %s 不存在", beanName);
    }

注册
调用方法

localhost:9000/bean/register/TestService

结果

执行操作Bean的方法，返回结果如下

TestService{name=‘张三’, id=‘1’}

修改
调用方法

localhost:9000/bean/update/TestService

结果

执行操作Bean的方法，返回结果如下

TestService{name=‘AL113A5’, id=‘12’}

移除
调用方法

localhost:9000/bean/remove/TestService

结果

执行操作Bean的方法，返回结果如下

Bean TestService 不存在