java如何多线程更新由sql代码更新的数据库？

Question

我制作了一个基本的CRUD spring启动应用程序，可以连接到Postgresql数据库。 我通过employeeDao中的sql代码访问数据库，该代码稍后在控制器中通过employeeService类调用。 我现在必须使用多线程方法更新数据库，但我不知道如何实现它

我做过任务执行者，但我没有；我真的不知道如何使用它

公共执行者任务执行者（）{

    final ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor();
    executor.setCorePoolSize(2);
    executor.setMaxPoolSize(2);
    executor.setQueueCapacity(50);
    executor.setThreadNamePrefix("EmployeeThread-");
    executor.initialize();
    return executor;
}

这是我的员工建议：

public class EmployeeDaoImpl implements EmployeeDao{

    public EmployeeDaoImpl(NamedParameterJdbcTemplate template) {  
        this.template = template;  
}  
    NamedParameterJdbcTemplate template;  

    @Override
    public List<Employee> findAll() {
        return template.query("select * from employee", new EmployeeRowMapper());
    }
    @Override
    public void insertEmployee(Employee emp) {
         final String sql = "insert into employee(employeeId, employeeName ) values(:employeeId,:employeeName)";

            KeyHolder holder = new GeneratedKeyHolder();
            SqlParameterSource param = new MapSqlParameterSource()
                    .addValue("employeeId", emp.getEmployeeId())
                    .addValue("employeeName", emp.getEmployeeName());
            template.update(sql,param, holder);

    }

    @Override
    public void updateEmployee(Employee emp) {
         final String sql = "update employee set employeeName=:employeeName where employeeId=:employeeId";

            KeyHolder holder = new GeneratedKeyHolder();
            SqlParameterSource param = new MapSqlParameterSource()
                    .addValue("employeeId", emp.getEmployeeId())
                    .addValue("employeeName", emp.getEmployeeName());
            template.update(sql,param, holder);

    }

    @Override
    public void executeUpdateEmployee(Employee emp) {
         final String sql = "update employee set employeeName=:employeeName where employeeId=:employeeId";


         Map<String,Object> map=new HashMap<String,Object>();  
         map.put("employeeId", emp.getEmployeeId());
         map.put("employeeName", emp.getEmployeeName());

         template.execute(sql,map,new PreparedStatementCallback<Object>() {  
                @Override  
                public Object doInPreparedStatement(PreparedStatement ps)  
                        throws SQLException, DataAccessException {  
                    return ps.executeUpdate();  
                }  
            });  


    }

    @Override
    public void deleteEmployee(Employee emp) {
         final String sql = "delete from employee where employeeId=:employeeId";


         Map<String,Object> map=new HashMap<String,Object>();  
         map.put("employeeId", emp.getEmployeeId());

         template.execute(sql,map,new PreparedStatementCallback<Object>() {  
                @Override  
                public Object doInPreparedStatement(PreparedStatement ps)  
                        throws SQLException, DataAccessException {  
                    return ps.executeUpdate();  
                }  
            });  


    }

}

这是我的控制器

@RestController
@RequestMapping("/postgressApp")
public class ApplicationController {

    @Resource 
    EmployeeService employeeService;

    @GetMapping(value = "/employeeList")
    public List<Employee> getEmployees() {
        return employeeService.findAll();

    }

    @PostMapping(value = "/createEmp")
    public void createEmployee(@RequestBody Employee emp) {
         employeeService.insertEmployee(emp);

    }
    @PutMapping(value = "/updateEmp")
    public void updateEmployee(@RequestBody Employee emp) {
         employeeService.updateEmployee(emp);

    }
    @PutMapping(value = "/executeUpdateEmp")
    public void executeUpdateEmployee(@RequestBody Employee emp) {
         employeeService.executeUpdateEmployee(emp);

    }

    @DeleteMapping(value = "/deleteEmpById")
    public void deleteEmployee(@RequestBody Employee emp) {
         employeeService.deleteEmployee(emp);

    }


}

我应该通过另一种方法（如Crud存储库）更改代码以更新数据库吗

Answer 1

通常情况下，对于实时应用程序，来自用户的httprequest可以在不同的线程中到达。因此，应用程序控制器将从多个线程中调用。你自己不需要做太多关于多线程的事情

为了模拟这种情况，可以使用executor服务从Runnable调用各种ApplicationController方法。为每个操作向执行者提交一个runnable

但是，您必须小心，业务逻辑允许这种操作顺序。例如，您不能在创建员工之前更新他/她。同样，删除员工后，您不能更新他/她

或者，您可以通过使每个runnable只对一名员工进行操作，并按顺序执行一系列操作，从而使其更加有序

要使用executor服务，您可能需要阅读有关submitTask、Shutdownow和awaitTermination的内容：https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ExecutorService.html

更快的介绍：http://tutorials.jenkov.com/java-util-concurrent/executorservice.html