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Spring 學習筆記（一）：基於 Java Config 的 IOC 容器構建與 MyBatis 整合

編輯：Java 綜合教學

Spring 學習筆記（一）：基於 Java Config 的 IOC 容器構建與 MyBatis 整合

本系列目標是構建一個完整的用戶註冊登入專案，技術棧：IntelliJ IDEA + Spring 4.3.1 + MyBatis 3.4 + MySQL + Maven。本篇聚焦於純 Java 代碼配置 IOC 容器與MyBatis 整合，摒棄傳統 XML 配置，體驗現代 Spring 開發模式。

一、專案初始化與依賴管理

1.1 Maven 專案結構

建立 maven-webapp 專案，目錄結構遵循標準約定：

src
├─ main
│  ├─ java
│  │  └─ com.everSeeker
│  │      ├─ config      // Java Config 類
│  │      ├─ dao         // MyBatis Mapper 接口
│  │      ├─ entity      // 實體類
│  │      └─ web         // Controller 等
│  └─ resources
│      ├─ mapper         // MyBatis XML 映射文件
│      ├─ db.properties  // 數據源配置
│      ├─ mybatis.xml    // MyBatis 核心配置
│      └─ spring-mybatis.xml // Spring-MyBatis 整合配置
└─ test

1.2 核心依賴 (pom.xml 節選)

<properties>
    <spring.version>4.3.1.RELEASE</spring.version>
</properties>

<dependencies>
    <!-- Spring Core -->
    <dependency><groupId>org.springframework</groupId><artifactId>spring-context</artifactId><version>${spring.version}</version></dependency>
    <dependency><groupId>org.springframework</groupId><artifactId>spring-jdbc</artifactId><version>${spring.version}</version></dependency>
    <dependency><groupId>org.springframework</groupId><artifactId>spring-webmvc</artifactId><version>${spring.version}</version></dependency>
    <dependency><groupId>org.springframework</groupId><artifactId>spring-test</artifactId><version>${spring.version}</version></dependency>

    <!-- MyBatis -->
    <dependency><groupId>org.mybatis</groupId><artifactId>mybatis</artifactId><version>3.4.1</version></dependency>
    <dependency><groupId>org.mybatis</groupId><artifactId>mybatis-spring</artifactId><version>1.3.0</version></dependency>

    <!-- Database -->
    <dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>6.0.3</version></dependency>
    <dependency><groupId>c3p0</groupId><artifactId>c3p0</artifactId><version>0.9.1.2</version></dependency>

    <!-- Validation -->
    <dependency><groupId>javax.validation</groupId><artifactId>validation-api</artifactId><version>1.1.0.Final</version></dependency>
    <dependency><groupId>org.hibernate</groupId><artifactId>hibernate-validator</artifactId><version>5.2.4.Final</version></dependency>

    <!-- Servlet/JSP -->
    <dependency><groupId>javax.servlet</groupId><artifactId>javax.servlet-api</artifactId><version>3.1.0</version></dependency>
    <dependency><groupId>javax.servlet</groupId><artifactId>jstl</artifactId><version>1.2</version></dependency>
</dependencies>

二、MyBatis 核心配置

2.1 數據源屬性文件 (db.properties)

db.mysql.driverClass=com.mysql.jdbc.Driver
db.mysql.jdbcUrl=jdbc:mysql://localhost:3306/register_notice?useUnicode=true&characterEncoding=utf-8&allowMultiQueries=true
db.mysql.user=root
db.mysql.password=333
# C3P0 連接池參數
db.minPoolSize=10
db.maxPoolSize=100
db.initialPoolSize=20
db.maxIdleTime=60
db.acquireIncrement=5
db.maxStatements=100
db.idleConnectionTestPeriod=60
db.acquireRetryAttempts=30
db.breakAfterAcquireFailure=true
db.testConnectionOnCheckout=false

2.2 MyBatis 核心配置 (mybatis.xml)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "https://mybatis.org/dtd/mybatis-3-config.dtd">
<configuration>
    <typeAliases>
        <package name="com.everSeeker.entity" />
    </typeAliases>
</configuration>

採用包掃描方式自動註冊別名，省去逐個 <typeAlias> 配置。

2.3 Spring-MyBatis 整合配置 (spring-mybatis.xml)

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

    <bean id="dataSource" class="com.mchange.v2.c3p0.ComboPooledDataSource" destroy-method="close">
        <property name="driverClass" value="${db.mysql.driverClass}"/>
        <property name="jdbcUrl" value="${db.mysql.jdbcUrl}"/>
        <property name="user" value="${db.mysql.user}"/>
        <property name="password" value="${db.mysql.password}"/>
        <!-- C3P0 連接池屬性注入省略 -->
    </bean>

    <bean id="sqlSessionFactory" class="org.mybatis.spring.SqlSessionFactoryBean"
          p:dataSource-ref="dataSource"
          p:configLocation="classpath:mybatis.xml"
          p:mapperLocations="classpath*:mapper/*Mapper.xml"/>

    <bean class="org.mybatis.spring.mapper.MapperScannerConfigurer">
        <property name="basePackage" value="com.everSeeker.dao"/>
        <property name="sqlSessionFactoryBeanName" value="sqlSessionFactory"/>
    </bean>

    <bean id="transactionManager" class="org.springframework.jdbc.datasource.DataSourceTransactionManager">
        <property name="dataSource" ref="dataSource"/>
    </bean>
    <tx:annotation-driven transaction-manager="transactionManager" proxy-target-class="true"/>
</beans>

關鍵點：

context:property-placeholder 優先載入屬性文件，確保後續 Bean 定義能解析 ${...} 佔位符。
mapperLocations="classpath*:mapper/*Mapper.xml" 使用 classpath* 掃描多模塊下的映射文件。
MapperScannerConfigurer 自動將 Mapper 接口掃描為 Spring Bean，無需手動配置。
啟用 @Transactional 註解驅動，proxy-target-class="true" 強制使用 CGLIB 代理類而非 JDK 動態代理。

三、實體與 Mapper 開發

3.1 User 實體類 (含 JSR-303 驗證註解)

package com.everSeeker.entity;

import javax.validation.constraints.*;
import java.util.Date;
import java.util.UUID;

public class User {
    @Size(min = 32, max = 32, message = "uuid 應為 32 位字符串")
    private String id;

    @Size(min = 1, max = 32, message = "賬號長度 1-32 位")
    private String username;

    @NotEmpty(message = "密碼不能為空")
    private String password;

    @NotEmpty(message = "email 不能為空")
    @Email(message = "email 格式不正確")
    private String email;

    @Size(min = 11, max = 11, message = "手機號長度 11 位")
    private String cellphone;

    private long regDate;

    public User() {
        this.id = UUID.randomUUID().toString().replaceAll("-", "");
        this.regDate = 0;
    }
    // 多構造器、Getter/Setter、toString 省略
}

3.2 UserDao 接口

package com.everSeeker.dao;

import com.everSeeker.entity.User;
import org.springframework.stereotype.Repository;

@Repository
public interface UserDao {
    void addUser(User user);
    User getUserByUsername(String username);
}

3.3 UserMapper.xml (放置於 src/main/resources/mapper/)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "https://mybatis.org/dtd/mybatis-3-mapper.dtd">
<mapper namespace="com.everSeeker.dao.UserDao">
    <resultMap id="ResultMapUser" type="com.everSeeker.entity.User"></resultMap>

    <insert id="addUser" parameterType="User">
        INSERT INTO user(id, username, password, email, cellphone, regDate)
        VALUES(#{id}, #{username}, #{password}, #{email}, #{cellphone}, #{regDate})
    </insert>

    <select id="getUserByUsername" parameterType="String" resultMap="ResultMapUser">
        SELECT * FROM user WHERE username=#{username}
    </select>
</mapper>

避坑提示：Mapper XML 必須置於 src/main/resources 目錄，若放在 src/main/java 下 Maven 編譯不會複製資源文件，導致運行時找不到映射文件報錯。

四、純 Java Config 構建 IOC 容器

4.1 根容器配置

package com.everSeeker.config;

import org.springframework.context.annotation.*;
import org.springframework.context.annotation.ComponentScan.Filter;
import org.springframework.core.type.filter.RegexPatternTypeFilter;
import java.util.regex.Pattern;

@Configuration
@ComponentScan(basePackages = {"com.everSeeker"},
        excludeFilters = @Filter(type = FilterType.CUSTOM, value = RootConfig.WebPackage.class))
@ImportResource({"classpath:spring-mybatis.xml"})
public class RootConfig {

    public static class WebPackage extends RegexPatternTypeFilter {
        public WebPackage() {
            super(Pattern.compile("com\\.everSeeker\\.web"));
        }
    }
}

解析：

@Configuration：標識配置類，等同於 <beans>。
@ComponentScan：啟用組件掃描，排除 web 包（Controller 由 Servlet 容器管理）。
@ImportResource：導入 XML 配置（MyBatis 整合暫時保留 XML，後續可全 Java Config 化）。

4.2 Web 容器初始化器 (替代 web.xml)

package com.everSeeker.config;

import org.springframework.web.servlet.support.AbstractAnnotationConfigDispatcherServletInitializer;
import javax.servlet.MultipartConfigElement;
import javax.servlet.ServletRegistration;
import java.io.IOException;

public class WebAppInitializer extends AbstractAnnotationConfigDispatcherServletInitializer {

    @Override
    protected String[] getServletMappings() {
        return new String[]{"/"}; // DispatcherServlet 攔截所有請求
    }

    @Override
    protected Class<?>[] getRootConfigClasses() {
        return new Class<?>[]{RootConfig.class}; // 業務層 Bean
    }

    @Override
    protected Class<?>[] getServletConfigClasses() {
        return new Class<?>[]{WebConfig.class}; // Web 層 Bean
    }

    @Override
    protected void customizeRegistration(ServletRegistration.Dynamic registration) {
        // 文件上傳限制：單文件 2MB，總請求 4MB，臨時目錄 /tmp/uploads
        registration.setMultipartConfig(new MultipartConfigElement("/tmp/uploads", 2097152, 4194304, 0));
    }
}

4.3 Web MVC 配置類

package com.everSeeker.config;

import org.springframework.context.annotation.*;
import org.springframework.web.servlet.config.annotation.*;
import org.springframework.web.servlet.view.InternalResourceViewResolver;
import org.springframework.web.multipart.support.StandardServletMultipartResolver;
import java.io.IOException;

@Configuration
@EnableWebMvc
@ComponentScan("com.everSeeker.web")
public class WebConfig extends WebMvcConfigurerAdapter {

    @Bean
    public InternalResourceViewResolver viewResolver() {
        InternalResourceViewResolver resolver = new InternalResourceViewResolver();
        resolver.setPrefix("/WEB-INF/views/");
        resolver.setSuffix(".jsp");
        resolver.setExposeContextBeansAsAttributes(true);
        return resolver;
    }

    @Bean
    public StandardServletMultipartResolver multipartResolver() throws IOException {
        return new StandardServletMultipartResolver();
    }

    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable(); // 靜態資源由容器默認 Servlet 處理
    }
}