SSM 学习第一天

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Bean构造(使用无参构造器)

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<bean id="user" class="org.ljguo.pojo.User"/>

测试

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// UserTest.java
import org.ljguo.pojo.User;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class UserTest {
    public static void main(String[] args) {
        ApplicationContext ac = new ClassPathXmlApplicationContext("classpath:beans.xml");
        User user = ac.getBean("user", User.class);
        System.out.println(user);
    }
}

依赖注入

setter 注入
  1. 基本数据类型注入 name value
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    <bean id="user" class="org.ljguo.pojo.User">
        <property name="age" value="221"/>
        <property name="username" value="ljguo"/>
    </bean>
  2. 引用类型注入 name ref
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    <bean id="user" class="org.ljguo.pojo.User">
        <property name="age" value="221"/>
        <property name="username" value="ljguo"/>
        <property name="classes" ref="class"/>
    </bean>

    <bean id="class" class="org.ljguo.pojo.Class" >
        <property name="className" value="hqyj" />
        <property name="location" value="511" />
    </bean>
  • 构造器注入
  1. 使用 name, name 表示构造器中形参的名字
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    <bean id="user" class="org.ljguo.pojo.User">
        <constructor-arg name="username" value="ljguo" />
        <constructor-arg name="age" value="21" />
        <constructor-arg name="classes" ref="class"/>
    </bean>
  2. 使用 type, type 表示构造器中形参的类型
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    <bean id="user" class="org.ljguo.pojo.User" >
        <constructor-arg type="java.lang.String" value="ljguo"/>
        <constructor-arg type="int" value="25"/>
        <constructor-arg type="org.ljguo.pojo.Class" ref="class"/>
    </bean>
  3. 使用 index, index 表示构造器形参索引
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    <bean id="user" class="org.ljguo.pojo.User">
        <constructor-arg index="0" value="ljguo"/>
        <constructor-arg index="1" value="26"/>
        <constructor-arg index="2" ref="class"/>
    </bean>

自动装配

集合注入

  • pojo 实体类
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    package org.ljguo.pojo;

    import java.util.Arrays;
    import java.util.List;
    import java.util.Map;
    import java.util.Set;

    public class Collection {
        private int[] array;
        private List<String> list;
        private Set<String> set;
        private Map<String,String> map;


        public int[] getArray() {
            return array;
        }

        public void setArray(int[] array) {
            this.array = array;
        }

        public List<String> getList() {
            return list;
        }

        public void setList(List<String> list) {
            this.list = list;
        }

        public Set<String> getSet() {
            return set;
        }

        public void setSet(Set<String> set) {
            this.set = set;
        }

        public Map<String, String> getMap() {
            return map;
        }

        public void setMap(Map<String, String> map) {
            this.map = map;
        }

        @Override
        public String toString() {
            return "Collection{" +
                    "array=" + Arrays.toString(array) +
                    ", list=" + list +
                    ", set=" + set +
                    ", map=" + map +
                    '}';
        }
    }
  • XML 配置依赖注入
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    <bean id="collection" class="org.ljguo.pojo.Collection">
        <property name="array">
            <array>
                <value>1</value>
                <value>2</value>
                <value>3</value>
            </array>
        </property>

        <property name="list">
            <list>
                <value>ljguo</value>
                <value>gxx</value>
                <value>marlin</value>
            </list>
        </property>

        <property name="map">
            <map>
                <entry key="name" value="ljguo"/>
                <entry key="age" value="21"/>
            </map>
        </property>

        <property name="set">
            <set>
                <value>ljguo</value>
                <value>ljguo</value>
                <value>gxx</value>
            </set>
        </property>
    </bean>
  • 测试类
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    package org.ljguo.test;

    import org.ljguo.pojo.Collection;
    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;

    public class CollectionTest {
        public static void main(String[] args) {
            ApplicationContext ac = new ClassPathXmlApplicationContext("classpath:beans.xml");
            Collection collection = ac.getBean("collection", Collection.class);
            System.out.println(collection);
        }
    }

小案例(链接数据库)

  • 导入druid依赖坐标
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    <!-- https://mvnrepository.com/artifact/com.alibaba/druid -->
    <dependency>
      <groupId>com.alibaba</groupId>
      <artifactId>druid</artifactId>
      <version>1.1.16</version>
    </dependency>
  • 配置xml依赖注入
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    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="com.mysql.jdbc.Driver"/>
        <property name="url" value="jdbc:mysql://localhost:3306/ljguo"/>
        <property name="username" value="root"/>
        <property name="password" value="20001020"/>
    </bean>
  • 测试
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    package org.ljguo.test;

    import org.springframework.context.ApplicationContext;
    import org.springframework.context.support.ClassPathXmlApplicationContext;

    import javax.sql.DataSource;

    public class JdbcTest {
        public static void main(String[] args) {
            ApplicationContext ac = new ClassPathXmlApplicationContext("classpath:application.xml");
            DataSource dataSource = ac.getBean("dataSource", DataSource.class);
            System.out.println(dataSource);
        }
    }

使用 properties 配置文件

加载 properties 文件
  • 开启名字空间 context
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    <beans xmlns="http://www.springframework.org/schema/beans"
           xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
           xmlns:context="http://www.springframework.org/schema/context"
           xsi:schemaLocation="
           http://www.springframework.org/schema/beans
           http://www.springframework.org/schema/beans/spring-beans.xsd
           http://www.springframework.org/schema/context
           http://www.springframework.org/schema/context/spring-context.xsd
            ">
  • 使用 context 空间加载
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    <context:property-placeholder location="classpath*:*.properties"/>
    这一行代码加载了所有的properties文件
    properties 文件内容如下
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    jdbc.driver=com.mysql.jdbc.Driver
    jdbc.url=jdbc:mysql://localhost:3306/ljguo
    jdbc.username=root
    jdbc.password=20001020
    xml 配置文件可优化为如下内容
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    <bean id="dataSource" class="com.alibaba.druid.pool.DruidDataSource">
        <property name="driverClassName" value="${jdbc.driver}"/>
        <property name="url" value="${jdbc.url}"/>
        <property name="username" value="${jdbc.username}"/>
        <property name="password" value="${jdbc.password}"/>
    </bean>

容器相关

  • BeanFactory 是 IOC 容器的顶层接口, 初始化BeanFactory对象时, 加载的 bean 延迟加载
  • ApplicationContext 接口是 Spring 容器的核心接口, 初始化时 bean 立即加载
  • ApplicationContext 接口的常用初始化类
    • ClassPathXmlApplicationContext
    • FileSystemXmlApplicationContext