Java是企业级应用开发中非常流行的编程语言，而Java框架则是帮助开发者快速构建高效、可靠应用的工具。本文将介绍Java开发中常用的四大框架：Spring、Hibernate、Struts和MyBatis，并提供相关代码示例。

1. Spring框架

Spring是一个功能强大的开源框架，广泛用于构建企业级应用。它提供了全面的基础架构支持，尤其是其依赖注入（DI）和面向切面编程（AOP）功能。

1.1 依赖注入示例

依赖注入是Spring的核心功能之一。下面是一个简单的示例：

配置文件（applicationContext.xml）

xml

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<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">

<bean id="myService" class="com.example.MyService"/>

<bean id="myApp" class="com.example.MyApp">

<property name="service" ref="myService"/>

</bean>

</beans>

Java代码

java

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package com.example;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MyApp {

private MyService service;

public void setService(MyService service) {

this.service = service;

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public void run() {

service.perform();

}

public static void main(String[] args) {

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

MyApp app = (MyApp) context.getBean("myApp");

app.run();

}

}

class MyService {

public void perform() {

System.out.println("Service is performing...");

}

}

2. Hibernate框架

Hibernate是一个开源的对象关系映射（ORM）框架，用于将Java对象映射到数据库表。它极大地简化了数据库操作。

2.1 基本CRUD操作示例

以下是使用Hibernate进行基本CRUD操作的示例：

配置文件（hibernate.cfg.xml）

xml

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<!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate Configuration DTD 3.0//EN"

"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">

<hibernate-configuration>

<session-factory>

<property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>

<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>

<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/mydb</property>

<property name="hibernate.connection.username">root</property>

<property name="hibernate.connection.password">password</property>

<property name="hibernate.hbm2ddl.auto">update</property>

<property name="hibernate.show_sql">true</property>

<mapping class="com.example.User"/>

</session-factory>

</hibernate-configuration>

实体类（User.java）

java

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package com.example;

import javax.persistence.Entity;

import javax.persistence.Id;

@Entity

public class User {

@Id

private int id;

private String name;

// Getters and setters

public int getId() { return id; }

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

public String getName() { return name; }

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

}

CRUD操作

java

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package com.example;

import org.hibernate.Session;

import org.hibernate.SessionFactory;

import org.hibernate.cfg.Configuration;

public class Main {

public static void main(String[] args) {

SessionFactory factory = new Configuration().configure().buildSessionFactory();

Session session = factory.openSession();

session.beginTransaction();

// Create

User user = new User();

user.setId(1);

user.setName("John Doe");

session.save(user);

// Read

User retrievedUser = session.get(User.class, 1);

System.out.println(retrievedUser.getName());

// Update

retrievedUser.setName("Jane Doe");

session.update(retrievedUser);

// Delete

session.delete(retrievedUser);

session.getTransaction().commit();

session.close();

}

}

3. Struts框架

Struts是一个基于MVC设计模式的Web应用框架，它简化了Java EE Web应用的开发过程。

3.1 基本示例

配置文件（struts-config.xml）

xml

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<!DOCTYPE struts-config PUBLIC "-//Apache Software Foundation//DTD Struts Configuration 1.3//EN"

"http://struts.apache.org/dtds/struts-config_1_3.dtd">

<struts-config>

<form-beans>

<form-bean name="userForm" type="com.example.UserForm"/>

</form-beans>

<action-mappings>

<action path="/login" type="com.example.LoginAction"

name="userForm" scope="request" validate="true"

input="/login.jsp">

<forward name="success" path="/welcome.jsp"/>

<forward name="failure" path="/login.jsp"/>

</action>

</action-mappings>

</struts-config>

Java代码

java

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package com.example;

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import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.apache.struts.action.Action;

import org.apache.struts.action.ActionForm;

import org.apache.struts.action.ActionForward;

import org.apache.struts.action.ActionMapping;

public class LoginAction extends Action {

public ActionForward execute(ActionMapping mapping, ActionForm form,

HttpServletRequest request, HttpServletResponse response) {

UserForm userForm = (UserForm) form;

if ("admin".equals(userForm.getUsername()) && "password".equals(userForm.getPassword())) {

return mapping.findForward("success");

} else {

return mapping.findForward("failure");

}

}

}

class UserForm extends ActionForm {

private String username;

private String 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; }

}

4. MyBatis框架

MyBatis是一款优秀的持久层框架，它简化了JDBC和数据库操作，使开发者可以专注于SQL本身。

4.1 基本示例

配置文件（mybatis-config.xml）

xml

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<!DOCTYPE configuration

PUBLIC "-//mybatis.org//DTD Config 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-config.dtd">

<configuration>

<environments default="development">

<environment id="development">

<transactionManager type="JDBC"/>

<dataSource type="POOLED">

<property name="driver" value="com.mysql.jdbc.Driver"/>

<property name="url" value="jdbc:mysql://localhost:3306/mydb"/>

<property name="username" value="root"/>

<property name="password" value="password"/>

</dataSource>

</environment>

</environments>

<mappers>

<mapper resource="com/example/UserMapper.xml"/>

</mappers>

</configuration>

映射文件（UserMapper.xml）

xml

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<!DOCTYPE mapper

PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN"

"http://mybatis.org/dtd/mybatis-3-mapper.dtd">

<mapper namespace="com.example.UserMapper">

<select id="selectUser" parameterType="int" resultType="com.example.User">

SELECT * FROM users WHERE id = #{id}

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<insert id="insertUser" parameterType="com.example.User">

INSERT INTO users (id, name) VALUES (#{id}, #{name})

</insert>

<update id="updateUser" parameterType="com.example.User">

UPDATE users SET name = #{name} WHERE id = #{id}

</update>

<delete id="deleteUser" parameterType="int">

DELETE FROM users WHERE id = #{id}

</delete>

</mapper>

Java代码

java

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package com.example;

import java.io.InputStream;

import org.apache.ibatis.io.Resources;

import org.apache.ibatis.session.SqlSession;

import org.apache.ibatis.session.SqlSessionFactory;

import org.apache.ibatis.session.SqlSessionFactoryBuilder;

public class Main {

public static void main(String[] args) throws Exception {

String resource = "mybatis-config.xml";

InputStream inputStream = Resources.getResourceAsStream(resource);

SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(inputStream);

try (SqlSession session = sqlSessionFactory.openSession()) {

UserMapper mapper = session.getMapper(UserMapper.class);

// Create

User newUser = new User();

newUser.setId(1);

newUser.setName("John Doe");

mapper.insertUser(newUser);

session.commit();

// Read

User user = mapper.selectUser(1);

System.out.println(user.getName());