Spring 基于注解装配依赖对象和引用外部文件读取数据库配置

喜欢ヅ旅行 2022-06-07 05:55 94阅读 0赞

1.常用的有四个注解:

\#Controller: 用于控制器的注解

\#Service : 用于service的注解

\#Component： 用于基本组件的注解

\#Repository：用于Dao层的注解

其实，对于spring来说，它根本无法识别controller，service等，它只知道只要你加了以上四个注解，它就帮你创建bean.

简单来说，就是如果你在控制器上使用Component注解，或者使用Repository注解也是可以的，四种注解可以混用

但是，我们一般都按照上方所示的规则来使用注解，这样代码才有可读性

2.默认命名规则

*  我们使用注解配置bean的时候，并没有指定bean的id，那么spring帮我们创建bean的时候会给一个默认的id，id为类名首字母小写。如UserDao-> userDao
 *  我们也可以指定bean的名称(id)，使用注解的value属性，如@Service(value=”myService”)
 *  value属性是注解的默认属性，可以省略，即@Service(“myService”)

3.扫描的配置

\#使用resource-pattern属性，配置扫描的条件

<context:component-scan base-package="com.sunline">
        </context:component-scan>

4.使用Autowired

一般情况下，controller和service是有关联关系的，service和DAO层是有关联关系的，我们使用autowired注解，在controller中装配service，在service中装配reponsitory

注意:

\#如果有多个类实现了TestService这个接口，那么autowired会自动装配哪个？

根据实现类的name，如其中一个实现类：@Service(“testService”)，那么就自动装配这个实现类，因为private TestService testService;

\#如果有多个实现类，但是没有指明name怎么办？

如果没有指明name，将会抛异常，但是我们可以使用@Qualifier注解来说明使用哪一个实现类

5.在实际开发中，数据库的配置信息，我们一般都写到db.properties中，方便修改

\#在src下创建db.properties文件

\#spring配置（记得先加入context命名空间）

\#使用`context:property-placeholder`声明数据库配置文件的位置

\#使用$\{\} 来读取配置文件中的属性值(类似EL表达式)``

<context:property-placeholder location="classpath:db.properties"/>

具体见代码

\#配置文件

db.properties

username=root
    password=123456
    driverClassName=com.mysql.jdbc.Driver
    url=jdbc\:mysql\://localhost\:3306/bank?characterEncoding\=UTF-8

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
    <beans
    	xmlns="http://www.springframework.org/schema/beans"
    	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xmlns:p="http://www.springframework.org/schema/p"
    	xmlns:context="http://www.springframework.org/schema/context"
    	xmlns:tx="http://www.springframework.org/schema/tx"
    	xsi:schemaLocation="http://www.springframework.org/schema/beans
    	                    http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
                            http://www.springframework.org/schema/context 
                            http://www.springframework.org/schema/context/spring-context-3.0.xsd">
                            
        
        <context:property-placeholder location="classpath:db.properties"/>
        
        
        
        <context:component-scan base-package="com.sunline">
        </context:component-scan>
    	<bean id="dataSource"
    		class="org.apache.commons.dbcp.BasicDataSource">
    		<property name="driverClassName"
    			value="${driverClassName}">
    		</property>
    		<property name="url"
    			value="${url}">
    		</property>
    		<property name="username" value="${username}"></property>
    		<property name="password" value="${password}"></property>
    	</bean>
    	<bean id="sessionFactory"
    		class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
    		<property name="dataSource">
    			<ref bean="dataSource" />
    		</property>
    		<property name="hibernateProperties">
    			<props>
    				<prop key="hibernate.dialect">
    					org.hibernate.dialect.MySQLDialect
    				</prop>
    				<prop key="dialect">
    				    org.hibernate.dialect.MySQLDialect
    				</prop>
                    <prop key="hibernate.hbm2ddl.auto">true</prop>
                    <prop key="hibernate.show_sql">true</prop> 
    			</props>
    		</property>
    		<property name="mappingResources">
    			<list>
    				<value>com/sunline/entity/User.hbm.xml</value>
    			</list>
    		</property>
    	</bean>
    </beans>

\#数据模型层

User.java

package com.sunline.entity;
    
    
    
    /**
     * User entity. @author MyEclipse Persistence Tools
     */
    
    public class User  implements java.io.Serializable {
    
    
        // Fields    
    
         private Integer userId;
         private String userName;
         private String userPassword;
         private String userKind;
         private Double userBalance;
         private String userStatus;
    
    
        // Constructors
    
        /** default constructor */
        public User() {
        }
    
    	/** minimal constructor */
        public User(String userName, String userPassword, String userKind, Double userBalance) {
            this.userName = userName;
            this.userPassword = userPassword;
            this.userKind = userKind;
            this.userBalance = userBalance;
        }
        
        /** full constructor */
        public User(String userName, String userPassword, String userKind, Double userBalance, String userStatus) {
            this.userName = userName;
            this.userPassword = userPassword;
            this.userKind = userKind;
            this.userBalance = userBalance;
            this.userStatus = userStatus;
        }
    
       
        // Property accessors
    
        public Integer getUserId() {
            return this.userId;
        }
        
        public void setUserId(Integer userId) {
            this.userId = userId;
        }
    
        public String getUserName() {
            return this.userName;
        }
        
        public void setUserName(String userName) {
            this.userName = userName;
        }
    
        public String getUserPassword() {
            return this.userPassword;
        }
        
        public void setUserPassword(String userPassword) {
            this.userPassword = userPassword;
        }
    
        public String getUserKind() {
            return this.userKind;
        }
        
        public void setUserKind(String userKind) {
            this.userKind = userKind;
        }
    
        public Double getUserBalance() {
            return this.userBalance;
        }
        
        public void setUserBalance(Double userBalance) {
            this.userBalance = userBalance;
        }
    
        public String getUserStatus() {
            return this.userStatus;
        }
        
        public void setUserStatus(String userStatus) {
            this.userStatus = userStatus;
        }
    }

User.hbm.xml

<?xml version="1.0" encoding="utf-8"?>
    <!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
    "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
    
    <hibernate-mapping>
        <class name="com.sunline.entity.User" table="user" catalog="bank">
            <id name="userId" type="java.lang.Integer">
                <column name="user_id" />
                <generator class="native"></generator>
            </id>
            <property name="userName" type="java.lang.String">
                <column name="user_name" length="50" not-null="true" />
            </property>
            <property name="userPassword" type="java.lang.String">
                <column name="user_password" length="50" not-null="true" />
            </property>
            <property name="userKind" type="java.lang.String">
                <column name="user_kind" length="50" not-null="true" />
            </property>
            <property name="userBalance" type="java.lang.Double">
                <column name="user_balance" precision="15" not-null="true" />
            </property>
            <property name="userStatus" type="java.lang.String">
                <column name="user_status" length="4" />
            </property>
        </class>
    </hibernate-mapping>

\#数据访问层

UserDao.java

package com.sunline.dao;
    
    import java.util.List;
    
    import javax.annotation.Resource;
    
    import org.hibernate.SessionFactory;
    import org.springframework.orm.hibernate3.support.HibernateDaoSupport;
    import org.springframework.stereotype.Repository;
    
    import com.sunline.entity.User;
    @Repository
    public class UserDao extends HibernateDaoSupport{
    	/*
    	 * 获取所有用户信息
    	 */
    	@SuppressWarnings("unchecked")
    	public List<User> findAll(){
    		String sql="from User";
    		List<User> list=this.getHibernateTemplate().find(sql);
    		return list;
    	}
    	
    	/*
    	 * 使用注解必须添加以下方式
    	 */
        @Resource  
        public void setSessionFacotry(SessionFactory sessionFacotry) {  
            super.setSessionFactory(sessionFacotry);  
        }  
    }

\#业务逻辑层

UserBiz.java

package com.sunline.biz;
    
    import java.util.List;
    
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.beans.factory.annotation.Qualifier;
    import org.springframework.stereotype.Service;
    
    import com.sunline.dao.UserDao;
    import com.sunline.entity.User;
    @Service
    public class UserBiz {
    	/*
    	 * 获取所有用户信息
    	 */
    	@Autowired
    	@Qualifier("userDao")            //使用@Qualifier注解来说明使用哪一个实现类
        UserDao userDao;
    	public List<User> findAll(){
    		return userDao.findAll();
    	}
    }

\#测试数据

Test.java

package com.sunline.test;
    
    import java.util.List;
    
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;
    import com.sunline.biz.UserBiz;
    import com.sunline.entity.User;
    
    public class Test {
    
    	/**
    	 * @param args
    	 */
    	public static void main(String[] args) {
    		// TODO Auto-generated method stub
            ApplicationContext ctx = new ClassPathXmlApplicationContext("applicationContext.xml");
            
            UserBiz userBiz = (UserBiz) ctx.getBean("userBiz");
            List<User> list = userBiz.findAll();
            for(User user : list){
            	System.out.println("用户的个人信息为:"+user.getUserName()+" "+user.getUserPassword()+" "+user.getUserKind()+" "+user.getUserBalance()+" "+user.getUserStatus());
            }
    	}
    
    }

\#截图:

![Center][]

[Center]: /images/20220607/b63c6dd0579245bd9afe450d413e28f2.png