Question

我，我是春天新手，我想做的是创建一个简单的应用程序，执行以下操作：

1-一个简单的oracle表上的简单crud，名为Dummy，有两个字段：id，numeric和descripcion，一个字符串

2 - 应用程序只有一个servlet。通过调用它，将打印所有虚拟行的列表。

那就是它。问题是在servlet中，我的存储库实例始终为null。

由于

这是我的代码：

PersistenceContext

package jpa_spring.configuracion;

import java.util.Properties;

import javax.persistence.EntityManagerFactory;
import javax.sql.DataSource;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.core.env.Environment;
import org.springframework.data.jpa.repository.config.EnableJpaRepositories;
import org.springframework.orm.jpa.JpaTransactionManager;
import org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean;
import org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter;
import org.springframework.transaction.annotation.EnableTransactionManagement;

import com.zaxxer.hikari.HikariConfig;
import com.zaxxer.hikari.HikariDataSource;

@Configuration
@EnableJpaRepositories(basePackages = {"jpa_spring.dominio"})
@EnableTransactionManagement
public class PersistenceContext {
    @Bean(destroyMethod="close")
    DataSource dataSource(Environment env) {
        HikariConfig dataSourceConfig = new HikariConfig();
        dataSourceConfig.setDriverClassName(env.getRequiredProperty("db.driver"));
        dataSourceConfig.setJdbcUrl(env.getRequiredProperty("db.url"));
        dataSourceConfig.setUsername(env.getRequiredProperty("db.username"));
        dataSourceConfig.setPassword(env.getRequiredProperty("db.password"));

        return new HikariDataSource(dataSourceConfig);
    }

    @Bean
    LocalContainerEntityManagerFactoryBean entityManagerFactory(DataSource dataSource, Environment env) {
        LocalContainerEntityManagerFactoryBean entityManagerFactoryBean = new LocalContainerEntityManagerFactoryBean();
        entityManagerFactoryBean.setDataSource(dataSource);
        entityManagerFactoryBean.setJpaVendorAdapter(new HibernateJpaVendorAdapter());
        entityManagerFactoryBean.setPackagesToScan("jpa_spring.dominio");

        Properties jpaProperties = new Properties();
        jpaProperties.put("hibernate.dialect", env.getRequiredProperty("hibernate.dialect"));    
        jpaProperties.put("hibernate.hbm2ddl.auto", env.getRequiredProperty("hibernate.hbm2ddl.auto")); 
        jpaProperties.put("hibernate.ejb.naming_strategy", env.getRequiredProperty("hibernate.ejb.naming_strategy") ); 
        jpaProperties.put("hibernate.show_sql", env.getRequiredProperty("hibernate.show_sql")); 
        jpaProperties.put("hibernate.format_sql", env.getRequiredProperty("hibernate.format_sql") );

        entityManagerFactoryBean.setJpaProperties(jpaProperties);
        return entityManagerFactoryBean;
    }

    @Bean
    JpaTransactionManager transactionManager(EntityManagerFactory entityManagerFactory) {
        JpaTransactionManager transactionManager = new JpaTransactionManager();
        transactionManager.setEntityManagerFactory(entityManagerFactory);
        return transactionManager;

    }
}

虚拟

package jpa_spring.dominio;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;

@Entity
@Table(name="DUMMY")
public class Dummy {    
    private Long id;
    private String descripcion;

    public String getDescripcion() {
        return descripcion;
    }
    public void setDescripcion(String descripcion) {
        this.descripcion = descripcion;
    }

    @Id
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
}

RepositorioDummy

package jpa_spring.dominio;

import org.springframework.data.repository.CrudRepository;

public interface RepositorioDummy extends CrudRepository<Dummy, Long> {}

JPASpringServlet

package jpa_spring.servlet;

import java.io.IOException;
import java.util.Iterator;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import jpa_spring.dominio.Dummy;
import jpa_spring.dominio.RepositorioDummy;

@Component
public class JPASpringServlet extends HttpServlet {
    @Autowired
    private  RepositorioDummy repositorio;
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Iterator<Dummy> it = repositorio.findAll().iterator();
        while (it.hasNext()) {
            Dummy d = it.next();
            System.out.println(d.getDescripcion());
        }

    }
}

Answer 1

如果您正在使用Spring MVC（并且很可能是您），Spring已经公开了一个servlet，它将为您处理所有http请求。由于它的作用是分派请求，因此称为DispatcherServlet。您可以在reference documentation中详细了解相关信息。然后，该servlet将使用HandlerMapping将传入请求映射到应该调用的方法。

您应该创建controller而不是创建servlet。然后，您可以使用@RequestMapping提取的RequestMappingHandlerMapping注释，HandlerMapping的实现。

simple spring jpa servlet示例，crudrepository实例为null

1 个答案: