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Spring Boot Crud操作示例 | Java Code Geeks

，在本教程中，我们将探讨spring框架的spring boot模块中的crud操作。

简介

Spring Boot是一个为spring框架提供快速应用程序开发功能的模块，包括自动配置，独立代码和生产就绪代码
它创建打包为jar的应用程序，并使用嵌入式servlet容器（例如Tomcat，Jetty或Undertow）直接启动。因此，无需部署war文件
它通过提供入门模板简化了maven配置，并有助于解决依赖冲突。它会自动识别所需的依赖项并在应用程序中导入它们
它有助于删除样板代码，额外注释和xml配置
它提供强大的批处理并管理其余端点
它提供了一个高效的jpa-starter库，可以有效地将应用程序与关系数据库连接起来

现在，让我们看看如何在spring boot模块中使用jpa-starter库与关系数据库进行通信来实现本教程。

创建Spring Boot应用程序

以下是开发应用程序所涉及的Maven依赖

在这里，我们指定Spring Boot，Spring Boot JPA和MySQL连接器的依赖项。Maven将自动解析其他依赖项。该更新文件将具有下面的代码。步骤。

    <!-- Spring boot web mvc jar -->
        <!-- Automatically adds tomcat and jackson-databind jars -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <!-- Spring boot jpa jar -->
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <!-- Mysql database jar -->
        <dependency>
            <groupId>mysql</groupId>
            <artifactId>mysql-connector-java</artifactId>
        </dependency>

在Springbootcrudoperation/src/main/resources/创建一个新的属性文件application.properties：并向其中添加以下代码。

## Spring datasource.
spring.datasource.driver.<b>class</b>=com.mysql.cj.jdbc.Driver
spring.datasource.url=jdbc:mysql:<font><i>//localhost:3306/paramount</i></font><font>
spring.datasource.username=root
spring.datasource.password=

## Hibernate properties.
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL5Dialect

## Show sql query.
spring.jpa.show-sql=<b>true</b>

## Hibernate ddl auto.
spring.jpa.hibernate.ddl-auto=validate
</font>

将以下代码添加到主类中以从main方法引导应用程序。永远记住，spring boot应用程序的入口点是包含@SpringBootApplication注释和静态main方法的类。

<b>package</b> com.ducat.springboot.<b>rest</b>;

<b>import</b> org.springframework.boot.SpringApplication;
<b>import</b> org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
<b>public</b> <b>class</b> Myapplication {

    <b>public</b> <b>static</b> <b>void</b> main(String[] args) {
        SpringApplication.run(Myapplication.<b>class</b>, args);
    }
}

将以下代码添加到员工模型类。

Employee.java：

<b>package</b> com.ducat.springboot.<b>rest</b>.model;

<b>import</b> javax.persistence.Entity;
<b>import</b> javax.persistence.GeneratedValue;
<b>import</b> javax.persistence.GenerationType;
<b>import</b> javax.persistence.Id;
<b>import</b> javax.persistence.Table;

<b>import</b> org.hibernate.annotations.DynamicInsert;
<b>import</b> org.hibernate.annotations.DynamicUpdate;
<b>import</b> org.springframework.stereotype.Component;

@Component

<font><i>// Spring jpa jars.</i></font><font>
@Entity
@Table(name= </font><font>"employee"</font><font>)

</font><font><i>// To increase speed and save sql statement execution time.</i></font><font>
@DynamicInsert
@DynamicUpdate
<b>public</b> <b>class</b> Employee {

    @Id
    @GeneratedValue(strategy= GenerationType.IDENTITY)
    <b>private</b> <b>int</b> id;
    <b>private</b> String name;
    <b>private</b> String department;
    <b>private</b> <b>double</b> salary;

    <b>public</b> Employee() { }

    <b>public</b> <b>int</b> getId() {
        <b>return</b> id;
    }
    <b>public</b> <b>void</b> setId(<b>int</b> id) {
        <b>this</b>.id = id;
    }
    <b>public</b> String getName() {
        <b>return</b> name;
    }
    <b>public</b> <b>void</b> setName(String name) {
        <b>this</b>.name = name;
    }
    <b>public</b> String getDepartment() {
        <b>return</b> department;
    }
    <b>public</b> <b>void</b> setDepartment(String department) {
        <b>this</b>.department = department;
    }
    <b>public</b> <b>double</b> getSalary() {
        <b>return</b> salary;
    }
    <b>public</b> <b>void</b> setSalary(<b>double</b> salary) {
        <b>this</b>.salary = salary;
    }

    @Override
    <b>public</b> String toString() {
        <b>return</b> </font><font>"Employee [id="</font><font> + id + </font><font>", name="</font><font> + name + </font><font>", department="</font><font> + department + </font><font>", salary="</font><font> + salary + </font><font>"]"</font><font>;
    }
}
</font>

将以下代码添加到扩展JPA存储库的Dao接口，以自动处理crud查询。

Mydaorepository.java

<b>package</b> com.ducat.springboot.<b>rest</b>.dao;

<b>import</b> org.springframework.data.jpa.repository.JpaRepository;
<b>import</b> org.springframework.stereotype.Repository;

<b>import</b> com.ducat.springboot.<b>rest</b>.model.Employee;

@Repository
<b>public</b> <b>interface</b> Mydaorepository <b>extends</b> JpaRepository<Employee, Integer> {

}

将以下代码添加到服务类中，我们将调用Dao接口的方法来处理sql操作。

@Service
<b>public</b> <b>class</b> Myserviceimpl implements Myservice {

    @Autowired
    Mydaorepository dao;

    @Override
    <b>public</b> List<Employee> getEmployees() {
        <b>return</b> dao.findAll();
    }
    @Override
    <b>public</b> Optional<Employee> getEmployeeById(<b>int</b> empid) {
        <b>return</b> dao.findById(empid);
    }
    @Override
    <b>public</b> Employee addNewEmployee(Employee emp) {
        <b>return</b> dao.save(emp);
    }
    @Override
    <b>public</b> Employee updateEmployee(Employee emp) {
        <b>return</b> dao.save(emp);
    }
    @Override
    <b>public</b> <b>void</b> deleteEmployeeById(<b>int</b> empid) {
        dao.deleteById(empid);
    }
    @Override
    <b>public</b> <b>void</b> deleteAllEmployees() {
        dao.deleteAll();
    }
}

将以下代码添加到旨在处理传入请求的控制器类中。该类使用注释进行@RestController注释，其中每个方法都将域对象作为json响应而不是视图返回。

<b>package</b> com.ducat.springboot.<b>rest</b>.controller;

<b>import</b> java.util.List;
<b>import</b> java.util.Optional;

<b>import</b> org.springframework.beans.factory.annotation.Autowired;
<b>import</b> org.springframework.web.bind.annotation.PathVariable;
<b>import</b> org.springframework.web.bind.annotation.RequestBody;
<b>import</b> org.springframework.web.bind.annotation.RequestMapping;
<b>import</b> org.springframework.web.bind.annotation.RequestMethod;
<b>import</b> org.springframework.web.bind.annotation.RestController;

<b>import</b> com.ducat.springboot.<b>rest</b>.model.Employee;
<b>import</b> com.ducat.springboot.<b>rest</b>.service.Myservice;

@RestController
<b>public</b> <b>class</b> Mycontroller {

    @Autowired
    Myservice service;

    @RequestMapping(value= <font>"/employee/all"</font><font>, method= RequestMethod.GET)
    <b>public</b> List<Employee> getEmployees() {
        System.out.println(<b>this</b>.getClass().getSimpleName() + </font><font>" - Get all employees service is invoked."</font><font>);
        <b>return</b> service.getEmployees();
    }

    @RequestMapping(value= </font><font>"/employee/{id}"</font><font>, method= RequestMethod.GET)
    <b>public</b> Employee getEmployeeById(@PathVariable <b>int</b> id) throws Exception {
        System.out.println(<b>this</b>.getClass().getSimpleName() + </font><font>" - Get employee details by id is invoked."</font><font>);

        Optional<Employee> emp =  service.getEmployeeById(id);
        <b>if</b>(!emp.isPresent())
            <b>throw</b> <b>new</b> Exception(</font><font>"Could not find employee with id- "</font><font> + id);

        <b>return</b> emp.get();
    }

    @RequestMapping(value= </font><font>"/employee/add"</font><font>, method= RequestMethod.POST)
    <b>public</b> Employee createEmployee(@RequestBody Employee newemp) {
        System.out.println(<b>this</b>.getClass().getSimpleName() + </font><font>" - Create new employee method is invoked."</font><font>);
        <b>return</b> service.addNewEmployee(newemp);
    }

    @RequestMapping(value= </font><font>"/employee/update/{id}"</font><font>, method= RequestMethod.PUT)
    <b>public</b> Employee updateEmployee(@RequestBody Employee updemp, @PathVariable <b>int</b> id) throws Exception {
        System.out.println(<b>this</b>.getClass().getSimpleName() + </font><font>" - Update employee details by id is invoked."</font><font>);

        Optional<Employee> emp =  service.getEmployeeById(id);
        <b>if</b> (!emp.isPresent())
            <b>throw</b> <b>new</b> Exception(</font><font>"Could not find employee with id- "</font><font> + id);

        </font><font><i>/* IMPORTANT - To prevent the overriding of the existing value of the variables in the database, 
         * if that variable is not coming in the @RequestBody annotation object. */</i></font><font>        
        <b>if</b>(updemp.getName() == <b>null</b> || updemp.getName().isEmpty())
            updemp.setName(emp.get().getName());
        <b>if</b>(updemp.getDepartment() == <b>null</b> || updemp.getDepartment().isEmpty())
            updemp.setDepartment(emp.get().getDepartment());
        <b>if</b>(updemp.getSalary() == 0)
            updemp.setSalary(emp.get().getSalary());

        </font><font><i>// Required for the "where" clause in the sql query template.</i></font><font>
        updemp.setId(id);
        <b>return</b> service.updateEmployee(updemp);
    }

    @RequestMapping(value= </font><font>"/employee/delete/{id}"</font><font>, method= RequestMethod.DELETE)
    <b>public</b> <b>void</b> deleteEmployeeById(@PathVariable <b>int</b> id) throws Exception {
        System.out.println(<b>this</b>.getClass().getSimpleName() + </font><font>" - Delete employee by id is invoked."</font><font>);

        Optional<Employee> emp =  service.getEmployeeById(id);
        <b>if</b>(!emp.isPresent())
            <b>throw</b> <b>new</b> Exception(</font><font>"Could not find employee with id- "</font><font> + id);

        service.deleteEmployeeById(id);
    }

    @RequestMapping(value= </font><font>"/employee/deleteall"</font><font>, method= RequestMethod.DELETE)
    <b>public</b> <b>void</b> deleteAll() {
        System.out.println(<b>this</b>.getClass().getSimpleName() + </font><font>" - Delete all employees is invoked."</font><font>);
        service.deleteAllEmployees();
    }
}
</font>

运行应用程序

当我们准备好所有更改时，让我们编译spring boot项目并将应用程序作为java项目运行。

使用Postman测试：

<font><i>// Get all employees</i></font><font>
http:</font><font><i>//localhost:8080/employee/all</i></font><font>

</font><font><i>// Get employee by id</i></font><font>
http:</font><font><i>//localhost:8080/employee/1003</i></font><font>

</font><font><i>// Create new employee</i></font><font>
http:</font><font><i>//localhost:8080/employee/add</i></font><font>

</font><font><i>// Update existing employee by id</i></font><font>
http:</font><font><i>//localhost:8080/employee/update/1008</i></font><font>

</font><font><i>// Delete employee by id</i></font><font>
http:</font><font><i>//localhost:8080/employee/delete/1002</i></font><font>

</font><font><i>// Delete all employees</i></font><font>
http:</font><font><i>//localhost:8080/employee/deleteall</i></font><font>
</font>

这就是本教程的全部内容，我希望这篇文章能为您提供所需的一切。快乐学习，别忘了分享！

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