Spring之 Auto-Wiring All Beans of Compatible Type

Posted 2020-06-13 A_Beaver

Auto-Wiring All Beans of Compatible Type

   @Autowired 注解按类型（type）依赖入住的时候，可以把类型兼容的所有类注入到数组、链表、map等集合数据结构中。如：mybatis中TypeHandler为例：

package com.doctor.practice01;

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public interface TypeHandler<T> {

    void setParameter(PreparedStatement ps, int i, T parameter, Object jdbcType) throws SQLException;

    T getResult(ResultSet rs, String columnName) throws SQLException;

    T getResult(ResultSet rs, int columnIndex) throws SQLException;

    T getResult(CallableStatement cs, int columnIndex) throws SQLException;

}

package com.doctor.practice01;

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.springframework.stereotype.Component;

/**
 * @author sdcuike
 *
 * @time 2016年2月10日 下午9:57:37
 */

@Component("String")
public class StringTypeHandler implements TypeHandler<String> {

    @Override
    public void setParameter(PreparedStatement ps, int i, String parameter, Object jdbcType) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public String getResult(ResultSet rs, String columnName) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public String getResult(ResultSet rs, int columnIndex) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public String getResult(CallableStatement cs, int columnIndex) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

}

package com.doctor.practice01;

import java.sql.CallableStatement;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Timestamp;

import org.springframework.stereotype.Component;

/**
 * @author sdcuike
 *
 * @time 2016年2月10日 下午9:58:23
 */

@Component("Timestamp")
public class SqlTimestampTypeHandler implements TypeHandler<Timestamp> {

    @Override
    public void setParameter(PreparedStatement ps, int i, Timestamp parameter, Object jdbcType) throws SQLException {
        // TODO Auto-generated method stub

    }

    @Override
    public Timestamp getResult(ResultSet rs, String columnName) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public Timestamp getResult(ResultSet rs, int columnIndex) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public Timestamp getResult(CallableStatement cs, int columnIndex) throws SQLException {
        // TODO Auto-generated method stub
        return null;
    }

    @Override
    public String toString() {
        // TODO Auto-generated method stub
        return super.toString();
    }

}

 简单例子，我们要把TypeHandler所有的子类，这里指的是StringTypeHandler、SqlTimestampTypeHandler注入到list和map数据结构中：

package com.doctor.practice01;

import java.util.List;
import java.util.Map;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

/**
 * @author sdcuike
 *
 * @time 2016年2月10日 下午10:00:26
 */

@Component
public class TypeHandlerUtil {

    @SuppressWarnings({ "rawtypes", "unused" })
    private static List<TypeHandler> typeHandlers;

    @SuppressWarnings({ "rawtypes", "unused" })
    private static Map<String, TypeHandler> typeHandlerMap;

    @Autowired
    @SuppressWarnings("rawtypes")
    public void setTypeHandlerMap(Map<String, TypeHandler> typeHandlerMap) {
        TypeHandlerUtil.typeHandlerMap = typeHandlerMap;
    }

    @Autowired
    @SuppressWarnings("rawtypes")
    public void setTypeHandlers(List<TypeHandler> typeHandlers) {
        TypeHandlerUtil.typeHandlers = typeHandlers;
    }

    public static Map<String, TypeHandler> getTypeHandlerMap() {
        return typeHandlerMap;
    }

    public static List<TypeHandler> getTypeHandlers() {
        return typeHandlers;
    }
}

我们测试一下：

package com.doctor.practice01;

import java.util.List;

import org.springframework.context.annotation.AnnotationConfigApplicationContext;

/**
 * @author sdcuike
 *
 * @time 2016年2月10日 下午9:49:16
 * 
 *       Auto-Wiring All Beans of Compatible Type
 * 
 * 
 */
public class AutoWiringAllBeansOfCompatibleType {
    public static void main(String[] args) {
        AnnotationConfigApplicationContext applicationContext = new AnnotationConfigApplicationContext();
        applicationContext.scan("com.doctor.practice01");
        applicationContext.refresh();
        TypeHandlerUtil typeHandlerUtil = applicationContext.getBean(TypeHandlerUtil.class);
        List<TypeHandler> typeHandlers = typeHandlerUtil.getTypeHandlers();
        typeHandlers.forEach(System.out::println);
        // [email protected]
        // [email protected]

        typeHandlerUtil.getTypeHandlerMap().forEach((k, v) -> System.out.println("k:" + k + " v:" + v));

        // k:Timestamp v:[email protected]
        // k:String v:[email protected]

    }
}

注：注入map数据结构的时候，k指的是bean的name。

这样，当我们增加了一个类型的子类的时候，扫描自动注入就带来了便利，而不用我们手动像mybatis一样，配置在一个TypeHandler xml文件中，读取配置的时候再放到一个map结构中，利用spring就带来了便利。