springBoot整合springdata Jpa的基本使用以及带条件的分页查询

﹏ヽ暗。殇╰゛Y 2022-04-25 00:34 474阅读 0赞

# 一、springBoot整合springData Jpa #

在application.properties中声明启用如下：

spring.datasource.name=root
    spring.datasource.password=123456
    spring.datasource.url=jdbc:mysql://localhost:3306/mst?useSSL=false
    spring.datasource.driver-class-name=com.mysql.jdbc.Driver
    spring.datasource.type=com.aliba
    #Spring Data JPA
    spring.jpa.database=MYSQL
    spring.jpa.hibernate.ddl-auto=update
    spring.jpa.database-platform=org.hibernate.dialect.MySQL5Dialect
    spring.jpa.show-sql=trueba.druid.pool.DruidDataSource

开启springData Jpa自动配置

pom.xml文件

<dependency>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-starter-data-jpa</artifactId>
            </dependency>

这里使用的Druid数据源，则创建配置类

@Configuration
    public class DruidConfig {
    
        @ConfigurationProperties(prefix = "spring.datasource")
        @Bean
        public DataSource druid(){
            return  new DruidDataSource();
        }
    
        /**
         * 配置Druid的监控
         *     1、配置一个管理后台的Servlet
         */
    
        @Bean
        public ServletRegistrationBean<StatViewServlet> statViewServlet(){
            ServletRegistrationBean<StatViewServlet> bean = new ServletRegistrationBean<>(new StatViewServlet(), "/druid/*");
            Map<String,String> initParams = new HashMap<>(5);
    
            initParams.put("loginUsername","admin");
            initParams.put("loginPassword","123456");
            //默认就是允许所有访问
            initParams.put("allow","");
            initParams.put("deny","localhost");
    
            bean.setInitParameters(initParams);
            return bean;
        }
    
    
        /**
         * 2、配置一个web监控的filter
         */
        @Bean
        public FilterRegistrationBean<WebStatFilter> webStatFilter(){
            FilterRegistrationBean<WebStatFilter> bean = new FilterRegistrationBean<>();
            bean.setFilter(new WebStatFilter());
    
            Map<String,String> initParams = new HashMap<>(5);
            initParams.put("exclusions","*.js,*.css,/druid/*");
    
            bean.setInitParameters(initParams);
    
            bean.setUrlPatterns(Collections.singletonList("/*"));
    
            return  bean;
        }
    
    }

# 二、jpa基本使用 #

### 1.方法名的使用 ###

只要满足一定的规范，方法名即可操作数据库。如：

public interface UserDao extends JpaRepository<User, Integer>, JpaSpecificationExecutor<User> {
        /**
         * findUserByUsernameAndPassword
         * @param name name
         * @param password password
         * @return User
         */
        User findUserByLoginNameAndPassword(String name, String password);
    
        /**
         * updataPasswordById
         * @param id id
         * @param newPasseord newPasseord
         */
        @Modifying
        @Query("update User u set u.password=:newPasseord where u.id=:id")
        void updatePasswordById(@Param("id") Integer id, @Param("newPasseord") String newPasseord);
    
        /**
         * deleteUserById
         * @param id id
         */
        @Modifying
        void deleteUserById(Integer id);
    
        /**
         * findUserById
         * @param id id
         * @return User
         */
        User findUserById(Integer id);
    }

如果你是用的idea则会提示。

注意：如果该方法是update或者delete必须在方法上加入注解@Modifying，insert不能使用该规范

### 2.@Query注解的使用 ###

如果方法较为麻烦，或者参数不按方法的顺序，则可使用该注解

@Modifying
        @Query("update User u set u.password=:newPasseord where u.id=:id")
        void updatePasswordById(@Param("id") Integer id, @Param("newPasseord") String newPasseord);

# 三、Jpa的带条件分页使用 #

使用Specification方法实现分页功能，该方法dao层必须继承JpaSpecificationExecutor接口

/**
         * 获取menu list
         * @return  List<Menu>
         *
         */
        @Override
        public List<Menu> getMenuList(HttpServletRequest request) {
            String pid1 = request.getParameter("pid");
            int pid = (pid1 == null || "".equals(pid1.trim())) ?-1:Integer.parseInt(pid1);
            String menuName = request.getParameter("menuname");
            String url = request.getParameter("url");
            String icon = request.getParameter("icon");
            String page1 = request.getParameter("page");
            int page = (page1 == null || "".equals(page1.trim()))?-1:Integer.parseInt(page1);
            String rows1 = request.getParameter("rows");
            int rows = (rows1 == null || "".equals(rows1.trim()))?-1:Integer.parseInt(rows1);
    
            Specification<Menu> specification = getMenuSpecification(pid, menuName, url, icon);
            int firstResult = (page -1) * rows;
            Pageable pageable = new PageRequest(firstResult, rows);
            return menuDao.findAll(specification,pageable).stream().collect(Collectors.toList());
        }
    
        /**
         * 带条件的分页查询
         * @param pid pid
         * @param menuName menuName
         * @param url url
         * @param icon icon
         * @return Specification
         */
        private Specification<Menu> getMenuSpecification(int pid, String menuName, String url, String icon) {
            return (Specification<Menu>) (root, criteriaQuery, criteriaBuilder) -> {
                Predicate predicate = criteriaBuilder.conjunction();
                if (pid != -1) {
                    predicate.getExpressions().add(criteriaBuilder.equal(root.get("pid"), pid));
                }
                if (menuName != null && !"".equals(menuName.trim())) {
                    predicate.getExpressions().add(criteriaBuilder.equal(root.get("menuname"), menuName));
                }
                if (url != null && !"".equals(url.trim())) {
                    predicate.getExpressions().add(criteriaBuilder.equal(root.get("url"), url));
                }
                if (icon != null && !"".equals(icon.trim())) {
                    predicate.getExpressions().add(criteriaBuilder.equal(root.get("icon"), icon));
                }
                return predicate;
            };
        }

注意：stream().collect(Collectors.toList());

这个方法是Java jdk1.8以后的版本才有的