Spring | 易学教程

Batch Insert with JPA and Spring

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问题 I'm using Spring Framework and JPA to insert beans into my database. I need to insert almost 8000 entities, and this can delay too much. Why should I disable "second level cache" in Hibernate hibernate.cache.use_second_level_cache false When I set a "hibernate.jdbc.batch_size 20" in Hibernate, will it insert my beans like this? INSERT INTO VALUES (1),(2),(3)...(20); INSERT INTO VALUES (21),(2),(3)...(40); The documentation says: "Hibernate disables insert batching at the JDBC level

SpringBoot项目新建遇到问题整理（一）

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1.新建了一个SpringBoot项目：只引用需要用到的spring boot相关的jar包,除此之外没有任何的配置启动application.java报错： APPLICATION FAILED TO START *************************** Description: Cannot determine embedded database driver class for database type NONE Action: If you want an embedded database please put a supported one on the classpath. If you have database settings to be loaded from a particular profile you may need to active it (no profiles are currently active). --——————>原因：因为spring boot只要你在pom中引入了spring-boot-starter-data-jpa，他就会默认需要加载数据库相关的配置你要是没有在配置文件中配置数据库相关信息，它会加载默认的配置（不存在的）然后就报错了，所以你要是要用数据库相关的东西你就完善配置不用数据库相关的东西

闲鱼服务端架构演进历程

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作者 | 万佳嘉宾 | 巴滕闲鱼是从阿里巴巴某一茶水间“游”出来的。2014 年 6 月，闲鱼诞生，2 年时间不到，其用户数突破 1 亿。如今，它已经成为国内最知名的闲置交易平台，拥有数亿用户，年交易额超过 2000 亿，并开启了一个万亿市场。闲鱼能有今天的成绩，离不开背后的技术迭代、架构升级和技术人的付出。闲鱼初创时，架构设计面临着哪些挑战？闲鱼服务端架构在 6 年时间里是怎样演进的？闲鱼在服务端架构上还在做哪些新尝试？...... 带着这些问题，InfoQ 记者采访了闲鱼技术部高级技术专家巴滕。自闲鱼创立以来，他一直参与闲鱼服务端架构持续演进的工作。 1、闲鱼的业务特点据巴滕介绍，闲鱼是一个典型的双边市场，买家和卖家规模相互影响，“如何同时服务好买家和卖家双方，这是我们一直努力的方向”。对买家来说，要提升商品发现效率，帮助他们尽快地买到商品。对卖家而言，要降低发布门槛，帮助他们尽快地把商品卖出去。对于平台，要持续优化用户的使用体验，比如降低纠纷和欺诈问题，同时持续扩大市场规模。 2、闲鱼服务端最初的架构设计众所周知，闲鱼的前身是 PC 时代的淘宝二手，它属于淘宝的一个小频道。当时，闲鱼整体业务规模和用户量都非常小。基本上，单一应用就支撑所有业务，并且整体架构和服务完全是面向 PC 设计的。 “当时，服务端同学需要时常编写 Velocity 模板代码

Spring boot 2.0.2, interception of Cloud Stream annotations with Aop not working anymore

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问题 I tried to keep the title as explicit and simple as possible. Basically, I need to intercept the usage of Cloud stream's @Input and @Output annotations. This is needed to automatically add a specific ChannelInterceptor to each MessageChannel. (The behaviour in the preSend method will be slightly different whether the message has been produced or consumed). For example, if I declare this advice @Around("@annotation(org.springframework.cloud.stream.annotation.Input)") public Object

Spring boot 2.0.2, interception of Cloud Stream annotations with Aop not working anymore

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How to fix 'java.lang.NoClassDefFoundError: org/apache/tinkerpop/gremlin/process/traversal/dsl/graph/GraphTraversalSource$GraphTraversalSourceStub'?

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问题 I am trying to initialize an in-memory graph using TinkerGraph. Firstly, i have defined the bean in my context xml file and tried to initialise the TinkerGraph. My intention is to unit test the classes that i have created for forming the gremlin queries, the end queries that i get from these classes are in the form of a string, so in order to execute them through the TinkerGraph, i have the used the approach given in the following post: Get Gremlin query as a String and execute it in java

UnknownHostException when trying to connect to heroku-postgres from local Springboot project with Spring JPA

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问题 I am trying to connect to heroku-postgres with Spring JPA when I am getting an unknownHostException. at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:292) ~[postgresql-42.2.5.jar:42.2.5] at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:49) ~[postgresql-42.2.5.jar:42.2.5] at org.postgresql.jdbc.PgConnection.<init>(PgConnection.java:195) ~[postgresql-42.2.5.jar:42.2.5] at org.postgresql.Driver.makeConnection(Driver.java

UnknownHostException when trying to connect to heroku-postgres from local Springboot project with Spring JPA

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UnknownHostException when trying to connect to heroku-postgres from local Springboot project with Spring JPA

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How to handle Spring Boot/ Spring Data projections with entity relationships (nested projection)

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问题 I'm trying to get nested projections working in Spring Boot. I have 2 entities, Parent and Child , wheras Parent has a unidirectional @OneToMany relationship to Child . Here are the classes: (using Lombok-Annotations) @Entity @Data @NoArgsConstructor public class Parent { @Id @GeneratedValue private long id; private String basic; private String detail; @OneToMany(fetch = FetchType.EAGER) private List<Child> children; public Parent(String basic, String detail, List<Child> children) { this

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