Spring学习笔记

一、Bean标签范围配置

singleton：只能创建一个对象，加载配置文件时创建一个bean对象，之后不再创建。
prototype：可以创建多个对象，每使用getBean方法时，创建一个对象。

二、注入引用类型

UserService会new一个引用对象UserDao，以此举例。

set方法注入

public class UserServiceImpl implements UserService {
    private UserDao userDao;
    public void setUserDao(UserDao userDao){
        this.userDao=userDao;
    }
    @Override
    public void run() {
        System.out.println("userService run");
        userDao.run();
    }
}

public class UserDaoImpl implements UserDao {
    @Override
    public void run() {
        System.out.println("userDao run");
    }
}

<bean id="userDao" class="com.moxb.dao.impl.UserDaoImpl"></bean>
<bean id="userService" class="com.moxb.service.Impl.UserServiceImpl">
    <!--第一个是setUserDao，第二个是UserDao类-->
     <property name="userDao" ref="userDao"></property>
</bean>

使用注解后必须用spring容器获取service对象，不然dao不会注入到service中，从而空指针异常。
使用p空间简化

<?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"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
        <bean id="userDao" class="com.moxb.dao.impl.UserDaoImpl"></bean>
        <!--UserDAO是类名-->
        <bean id="userService" class="com.moxb.service.Impl.UserServiceImpl" p:userDao-ref="userDao"/>
</beans>

构造方法注入

public class UserServiceImpl implements UserService {
    private UserDao userDao;

    public UserServiceImpl() {
    }

    public UserServiceImpl(UserDao userDao) {
        this.userDao = userDao;
    }

    @Override
    public void run() {
        System.out.println("userService run");
        userDao.run();
    }
}

<bean id="userDao" class="com.moxb.dao.impl.UserDaoImpl"></bean>
<bean id="userService" class="com.moxb.service.Impl.UserServiceImpl">
     <constructor-arg name="userDao" ref="userDao"></constructor-arg>
</bean>

三、注入普通类型

把上文中的ref换成value即可。

四、注入集合类型

可供选择的集合有

在property或者constructor-arg标签内使用。

五、三种注入方法综合使用案例

public class User {
    private String userName;
    private String password;

    public User() {
    }

    public User(String userName, String password) {
        this.userName = userName;
        this.password = password;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "userName='" + userName + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

public class UserDaoImpl implements UserDao {
    private List<User> userList;
    private Map<String,User> userMap;

    public void setUserList(List<User> userList) {
        this.userList = userList;
    }

    public void setUserMap(Map<String, User> userMap) {
        this.userMap = userMap;
    }

    @Override
    public String toString() {
        return "UserDaoImpl{\n" +
                "   userList=" + userList +
                "\n   userMap=" + userMap +
                "\n}";
    }

    @Override
    public void run() {
        System.out.println("userDao run");
        System.out.println(this);
    }
}

public class UserServiceImpl implements UserService {
    private UserDao userDao;

    public void setUserDao(UserDao userDao) {
        this.userDao = userDao;
    }

    @Override
    public void run() {
        System.out.println("userService run");
        userDao.run();
    }
}

public class SpringTest {
    @Test
    public void Test(){
        ApplicationContext app =new ClassPathXmlApplicationContext("applicationContext.xml");
        UserService service = (UserService)app.getBean("userService");
        service.run();
    }
}

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">
        <!--注入普通类型-->
        <bean id="user1" class="com.moxb.bean.User">
                <property name="userName" value="Alice"/>
                <property name="password" value="123456"/>
        </bean>
        <!--注入普通类型-->
        <bean id="user2" class="com.moxb.bean.User">
                <property name="userName" value="Bob"/>
                <property name="password" value="123456"/>
        </bean>
        <!--注入集合类型-->
        <bean id="userDao" class="com.moxb.dao.impl.UserDaoImpl">
                <property name="userList">
                        <list>
                                <ref bean="user1"/>
                                <ref bean="user2"/>
                        </list>
                </property>
                <property name="userMap">
                        <map>
                                <entry key="user1" value-ref="user1"/>
                                <entry key="user2" value-ref="user2"/>
                        </map>
                </property>
        </bean>
        <!--注入引用类型-->
        <bean id="userService" class="com.moxb.service.Impl.UserServiceImpl">
                <property name="userDao" ref="userDao"/>
        </bean>
</beans>

输出：

userService run
userDao run
UserDaoImpl{
   userList=[User{userName='Alice', password='123456'}, User{userName='Bob', password='123456'}]
   userMap={user1=User{userName='Alice', password='123456'}, user2=User{userName='Bob', password='123456'}}
}

六、Spring注解

七、Spring集成web环境

①配置ContextLoarderListener监听器

<!--pom.xml-->
<dependency>
   <groupId>org.springframework</groupId>
   <artifactId>spring-web</artifactId>
   <version>5.0.5.RELEASE</version>
</dependency>

<!--web.xml-->
    <context-param>
    <!--神坑！！！！这个名字不能随便取！！！！！-->
        <param-name>contextConfigLocation</param-name>
        <param-value>classpath:applicationContext.xml</param-value>
    </context-param>
    <listener>
        <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
    </listener>

②使用WebApplicationContextUtils获取上下文

protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
   ApplicationContext app = WebApplicationContextUtils.getWebApplicationContext(this.getServletContext());    
}