七、Spring 整合Web项目

7.1 整合思路

目前为止，每次获取对象，都必须先创建IOC容器，操作如下：

ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");

但这种操作如果放在一个项目中效率太低，IOC容器的初始化工作应该是提前准备好，并且是一次性的。在Web项目中，把加载Spring配置文件和创建IOC容器的过程，放在服务器启动时候完成。

实现思路如下：
1、在服务器启动时，为每个项目创建一个ServletContext对象；
2、使用监听器，监听ServletContext对象的创建；
3、监听器监听到ServletContext创建时候，加载Spring核心配置文件；
4、把IOC容器存放到SetvletContext域对象中；
5、需要获取对象时，从ServletContext域取出IOC容器；

7.2. 实现步骤

7.2.1 引入maven依赖

<dependencies>
    <!-- servlet-api -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>javax.servlet-api</artifactId>
        <version>3.1.0</version>
        <scope>provided</scope>
    </dependency>
    <!-- jsp-api -->
    <dependency>
        <groupId>javax.servlet.jsp</groupId>
        <artifactId>jsp-api</artifactId>
        <version>2.1</version>
        <scope>provided</scope>
    </dependency>
    <!-- jstl -->
    <dependency>
        <groupId>javax.servlet</groupId>
        <artifactId>jstl</artifactId>
        <version>1.2</version>
    </dependency>

    <!-- spring核心包-->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>4.3.18.RELEASE</version>
    </dependency>
    <!-- springbean包 -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-beans</artifactId>
        <version>4.3.18.RELEASE</version>
    </dependency>
    <!-- springcontext包 -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context</artifactId>
        <version>4.3.18.RELEASE</version>
    </dependency>
    <!-- spring表达式包 -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-expression</artifactId>
        <version>4.3.18.RELEASE</version>
    </dependency>
    <!-- springAOP包 -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-aop</artifactId>
        <version>4.3.18.RELEASE</version>
    </dependency>
    <!-- springAspects包 -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-aspects</artifactId>
        <version>4.3.18.RELEASE</version>
    </dependency>
    <!-- spring对web的支持包 -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-web</artifactId>
        <version>4.3.18.RELEASE</version>
    </dependency>
    <!-- springJDBC包 -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-jdbc</artifactId>
        <version>4.3.18.RELEASE</version>
    </dependency>
    <!-- spring事务包 -->
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-tx</artifactId>
        <version>4.3.18.RELEASE</version>
    </dependency>
    <!-- mysql驱动 -->
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
        <version>5.1.49</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
        <scope>test</scope>
    </dependency>
</dependencies>

7.2.2 监听器的实现

@WebListener
public class SpringContextListener implements ServletContextListener {
    @Override
    public void contextInitialized(ServletContextEvent servletContextEvent) {
        /**
         * 在web项目中的上下对象创建之后，将spring的IOC容器放置在上下文对象
         */
        //1.获取上下文对象
        ServletContext sc = servletContextEvent.getServletContext();
        //2.创建IOC容器
        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        //3.将容器对象放入到上下文域中
        sc.setAttribute("ac", ac);
    }

    @Override
    public void contextDestroyed(ServletContextEvent servletContextEvent) {

    }
}

7.2.3 Bean对象

@Component
public class Person {
    @Value("101")
    private Integer id;
    @Value("小明")
    private String name;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    @Override
    public String toString() {
        return "Person{" +
                "id=" + id +
                ", name='" + name + '\'' +
                '}';
    }
}

7.2.4 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:util="http://www.springframework.org/schema/util"
    xmlns:p="http://www.springframework.org/schema/p"
    xmlns:context="http://www.springframework.org/schema/context"
    xmlns:aop="http://www.springframework.org/schema/aop"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/util
    http://www.springframework.org/schema/util/spring-util.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context.xsd
    http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop.xsd">

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

7.2.5 Servlet

@WebServlet("/getPerson")
public class PersonServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        //1.取出容器
        ApplicationContext ac = (ApplicationContext) this.getServletContext().getAttribute("ac");

        //2.容器中获取对象
        Person person = ac.getBean("person", Person.class);

        System.out.println(person.getId() + "---" + person.getName());
    }
}

7.2.6 web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>
</web-app>

7.3 Spring中的实现

在Spring中已经实现了初始化IOC容器的监听器，需要导入Spring整合web项目的jar包。

web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <!-- 初始化IOC容器的spring中的监听器 -->
    <!--
        此监听器在创建IOC容器时，默认读取spring配置文件的位置是：/WEB-INF/applicationContext.xml
    -->
    <!-- 通过上下文初始化参数修改spring默认配置文件的位置及名称 -->
    <context-param>
        <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>
</web-app>

Spring在Web项目中使用的容器为：WebApplicationContext

//从上下文对象中获取IOC容器对象
WebApplicationContext ac = WebApplicationContextUtils.getWebApplicationContext(this.getServletContext());

Person person = ac.getBean("person", Person.class);
System.out.println(person.getId() + "---" + person.getName());

7.4 Web项目的完整实现

7.4.1 applicationContext.xml

db.properties：

# Oracle相关配置
jdbc.oracle.driver=oracle.jdbc.driver.OracleDriver
jdbc.oracle.url=jdbc:oracle:thin:@localhost:1521:orcl
jdbc.oracle.username=scott
jdbc.oracle.password=tiger

# Mysql相关配置
jdbc.mysql.driver=com.mysql.jdbc.Driver
jdbc.mysql.url=jdbc:mysql://localhost:3306/ssm?characterEncoding=utf8&useSSL=false
jdbc.mysql.username=root
jdbc.mysql.password=root

<?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:util="http://www.springframework.org/schema/util"
        xmlns:p="http://www.springframework.org/schema/p"
        xmlns:context="http://www.springframework.org/schema/context"
        xmlns:aop="http://www.springframework.org/schema/aop"
        xmlns:tx="http://www.springframework.org/schema/tx"
        xsi:schemaLocation="http://www.springframework.org/schema/beans
    http://www.springframework.org/schema/beans/spring-beans.xsd
    http://www.springframework.org/schema/util
    http://www.springframework.org/schema/util/spring-util.xsd
    http://www.springframework.org/schema/context
    http://www.springframework.org/schema/context/spring-context.xsd
    http://www.springframework.org/schema/aop
    http://www.springframework.org/schema/aop/spring-aop.xsd
    http://www.springframework.org/schema/tx
    http://www.springframework.org/schema/tx/spring-tx.xsd">

    <!--开启注解，扫描公共包com.newcapec-->
    <context:component-scan base-package="com.newcapec"/>

    <!--配置数据源-->
    <context:property-placeholder location="classpath:db.properties"/>

    <bean id="dataSource" class="org.springframework.jdbc.datasource.DriverManagerDataSource">
        <property name="driverClassName" value="${jdbc.mysql.driver}"/>
        <property name="url" value="${jdbc.mysql.url}"/>
        <property name="username" value="${jdbc.mysql.username}"/>
        <property name="password" value="${jdbc.mysql.password}"/>
    </bean>

    <!--配置jdbcTemplate-->
    <bean id="jdbcTemplate" class="org.springframework.jdbc.core.JdbcTemplate">
        <property name="dataSource" ref="dataSource"/>
    </bean>

</beans>

web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <!-- 初始化IOC容器的spring中的监听器 -->
    <!--
        此监听器在创建IOC容器时，默认读取spring配置文件的位置是：/WEB-INF/applicationContext.xml
    -->
    <!-- 通过上下文初始化参数修改spring默认配置文件的位置及名称 -->
    <context-param>
        <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>
</web-app>

7.4.2 实体类

@Component
public class Student {

    private Integer id;
    private String name;
    private Integer age;
    private String major;

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public Integer getAge() {
        return age;
    }

    public void setAge(Integer age) {
        this.age = age;
    }

    public String getMajor() {
        return major;
    }

    public void setMajor(String major) {
        this.major = major;
    }

    @Override
    public String toString() {
        return "Student{" +
                "id=" + id +
                ", name='" + name + '\'' +
                ", age=" + age +
                ", major='" + major + '\'' +
                '}';
    }
}

7.4.3 Dao

sql语句：

CREATE TABLE `t_student`  (
  `id` int(11) NOT NULL AUTO_INCREMENT COMMENT '学生id',
  `name` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '学生姓名',
  `age` int(2) NULL DEFAULT NULL COMMENT '学生性别',
  `major` varchar(20) CHARACTER SET utf8 COLLATE utf8_general_ci NULL DEFAULT NULL COMMENT '学生专业',
  PRIMARY KEY (`id`) USING BTREE
) ENGINE = InnoDB AUTO_INCREMENT = 5 CHARACTER SET = utf8 COLLATE = utf8_general_ci ROW_FORMAT = Compact;

-- ----------------------------
-- Records of t_student
-- ----------------------------
INSERT INTO `t_student` VALUES (2, '小红', 1, '网络工程');
INSERT INTO `t_student` VALUES (3, 'tom', 12, '计算机');
INSERT INTO `t_student` VALUES (4, '曹操', 12, '挖墓');

SET FOREIGN_KEY_CHECKS = 1;

接口：

public interface StudentDao {
    void insertStudent(Student student);

    void updateStudent(Student student);

    void deleteStudent(Integer id);

    Student selectStudentById(Integer id);

    List<Student> selectStudent();
}

实现类：

@Repository("studentDao")
public class StudentDaoImpl implements StudentDao {

    @Autowired
    private JdbcTemplate jdbcTemplate;

    @Override
    public void insertStudent(Student student) {
        //String sql = "insert into t_student(id,name,age,major) values(seq_demo.nextval,?,?,?)";
        String sql = "insert into t_student(name,age,major) values(?,?,?)";
        jdbcTemplate.update(sql, student.getName(), student.getAge(), student.getMajor());
    }

    @Override
    public void updateStudent(Student student) {
        String sql = "update t_student set name=?,age=?,major=? where id=?";
        jdbcTemplate.update(sql, student.getName(), student.getAge(), student.getMajor(), student.getId());
    }

    @Override
    public void deleteStudent(Integer id) {
        String sql = "delete from t_student where id=?";
        jdbcTemplate.update(sql, id);
    }

    @Override
    public Student selectStudentById(Integer id) {
        String sql = "select id,name,age,major from t_student where id=?";
        RowMapper<Student> rowMapper = new BeanPropertyRowMapper<>(Student.class);
        return jdbcTemplate.queryForObject(sql, rowMapper, id);
    }

    @Override
    public List<Student> selectStudent() {
        String sql = "select id,name,age,major from t_student order by id desc";
        RowMapper<Student> rowMapper = new BeanPropertyRowMapper<>(Student.class);
        return jdbcTemplate.query(sql, rowMapper);
    }
}

7.4.3 Service