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Eric Harmeling
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Spring Boot JDBC tutorial
1 parent 252a105 commit e60cf60

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‎_includes/sidebar-data-v20.1.json‎

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}
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]
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},
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{
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"title": "Roach Data",
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"items": [
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{
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"title": "Spring Boot with JDBC",
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"urls": [
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"/${VERSION}/build-a-spring-app-with-cockroachdb-jdbc.html"
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]
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}
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]
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},
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{
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"title": "Multi-Region",
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"items": [

‎_includes/v20.1/app/spring-data-jdbc/Account.java‎

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package io.roach.data.jdbc;
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import java.math.BigDecimal;
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import org.springframework.data.annotation.Id;
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/**
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* Domain entity mapped to the account table.
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*/
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public class Account {
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@Id
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private Long id;
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private String name;
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private AccountType type;
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private BigDecimal balance;
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public Long getId() {
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return id;
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}
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public String getName() {
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return name;
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}
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public AccountType getType() {
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return type;
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}
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public BigDecimal getBalance() {
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return balance;
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}
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}

‎_includes/v20.1/app/spring-data-jdbc/AccountController.java‎

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package io.roach.data.jdbc;
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import java.math.BigDecimal;
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import org.springframework.beans.factory.annotation.Autowired;
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import org.springframework.dao.DataRetrievalFailureException;
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import org.springframework.data.domain.PageRequest;
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import org.springframework.data.domain.Pageable;
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import org.springframework.data.domain.Sort;
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import org.springframework.data.web.PageableDefault;
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import org.springframework.data.web.PagedResourcesAssembler;
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import org.springframework.hateoas.IanaLinkRelations;
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import org.springframework.hateoas.Link;
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import org.springframework.hateoas.PagedModel;
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import org.springframework.hateoas.RepresentationModel;
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import org.springframework.hateoas.server.RepresentationModelAssembler;
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import org.springframework.http.HttpEntity;
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import org.springframework.http.HttpStatus;
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import org.springframework.http.ResponseEntity;
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import org.springframework.transaction.annotation.Transactional;
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import org.springframework.web.bind.annotation.*;
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import org.springframework.web.servlet.support.ServletUriComponentsBuilder;
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import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.linkTo;
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import static org.springframework.hateoas.server.mvc.WebMvcLinkBuilder.methodOn;
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import static org.springframework.transaction.annotation.Propagation.REQUIRES_NEW;
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/**
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* Main remoting and transaction boundary in the form of a REST controller. The discipline
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* when following the entity-control-boundary (ECB) pattern is that only service boundaries
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* are allowed to start and end transactions. A service boundary can be a controller, business
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* service facade or service activator (JMS/Kafka listener).
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* <p>
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* This is enforced by the REQUIRES_NEW propagation attribute of @Transactional annotated
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* controller methods. Between the web container's HTTP listener and the transaction proxy,
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* there's yet another transparent proxy in the form of a retry loop advice with exponential
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* backoff. It takes care of retrying transactions that are aborted by transient SQL errors,
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* rather than having these propagate all the way over the wire to the client / user agent.
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*
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* @see RetryableTransactionAspect
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*/
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@RestController
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public class AccountController {
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@Autowired
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private AccountRepository accountRepository;
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@Autowired
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private PagedResourcesAssembler<Account> pagedResourcesAssembler;
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/**
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* Provides the service index resource representation which is only links
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* for clients to follow.
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*/
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@GetMapping
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public ResponseEntity<RepresentationModel> index() {
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RepresentationModel index = new RepresentationModel();
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// Type-safe way to generate URLs bound to controller methods
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index.add(linkTo(methodOn(AccountController.class)
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.listAccounts(PageRequest.of(0, 5)))
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.withRel("accounts")); // Lets skip curies and affordances for now
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// This rel essentially informs the client that a POST to its href with
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// form parameters will transfer funds between referenced accounts.
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// (its only a demo)
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index.add(linkTo(AccountController.class)
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.slash("transfer{?fromId,toId,amount}")
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.withRel("transfer"));
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// Spring boot actuators for observability / monitoring
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index.add(new Link(
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ServletUriComponentsBuilder
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.fromCurrentContextPath()
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.pathSegment("actuator")
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.buildAndExpand()
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.toUriString()
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).withRel("actuator"));
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return new ResponseEntity<>(index, HttpStatus.OK);
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}
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/**
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* Provides a paged representation of accounts (sort order omitted).
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*/
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@GetMapping("/account")
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@Transactional(propagation = REQUIRES_NEW)
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public HttpEntity<PagedModel<AccountModel>> listAccounts(
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@PageableDefault(size = 5, direction = Sort.Direction.ASC) Pageable page) {
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return ResponseEntity
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.ok(pagedResourcesAssembler.toModel(accountRepository.findAll(page), accountModelAssembler()));
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}
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/**
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* Provides a point lookup of a given account.
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*/
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@GetMapping(value = "/account/{id}")
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@Transactional(propagation = REQUIRES_NEW, readOnly = true) // Notice its marked read-only
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public HttpEntity<AccountModel> getAccount(@PathVariable("id") Long accountId) {
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return new ResponseEntity<>(accountModelAssembler().toModel(
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accountRepository.findById(accountId)
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.orElseThrow(() -> new DataRetrievalFailureException("No such account: " + accountId))),
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HttpStatus.OK);
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}
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/**
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* Main funds transfer method.
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*/
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@PostMapping(value = "/transfer")
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@Transactional(propagation = REQUIRES_NEW)
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public HttpEntity<BigDecimal> transfer(
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@RequestParam("fromId") Long fromId,
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@RequestParam("toId") Long toId,
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@RequestParam("amount") BigDecimal amount
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) {
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if (amount.compareTo(BigDecimal.ZERO) < 0) {
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throw new IllegalArgumentException("Negative amount");
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}
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if (fromId.equals(toId)) {
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throw new IllegalArgumentException("From and to accounts must be different");
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}
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BigDecimal fromBalance = accountRepository.getBalance(fromId).add(amount.negate());
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// Application level invariant check.
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// Could be enhanced or replaced with a CHECK constraint like:
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// ALTER TABLE account ADD CONSTRAINT check_account_positive_balance CHECK (balance >= 0)
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if (fromBalance.compareTo(BigDecimal.ZERO) < 0) {
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throw new NegativeBalanceException("Insufficient funds " + amount + " for account " + fromId);
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}
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accountRepository.updateBalance(fromId, amount.negate());
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accountRepository.updateBalance(toId, amount);
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return ResponseEntity.ok().build();
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}
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private RepresentationModelAssembler<Account, AccountModel> accountModelAssembler() {
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return (entity) -> {
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AccountModel model = new AccountModel();
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model.setName(entity.getName());
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model.setType(entity.getType());
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model.setBalance(entity.getBalance());
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model.add(linkTo(methodOn(AccountController.class)
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.getAccount(entity.getId())
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).withRel(IanaLinkRelations.SELF));
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return model;
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};
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}
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}

‎_includes/v20.1/app/spring-data-jdbc/AccountModel.java‎

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package io.roach.data.jdbc;
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import java.math.BigDecimal;
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import org.springframework.hateoas.RepresentationModel;
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import org.springframework.hateoas.server.core.Relation;
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/**
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* Account resource represented in HAL+JSON via REST API.
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*/
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@Relation(value = "account", collectionRelation = "accounts")
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public class AccountModel extends RepresentationModel<AccountModel> {
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private String name;
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private AccountType type;
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private BigDecimal balance;
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public String getName() {
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return name;
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}
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public void setName(String name) {
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this.name = name;
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}
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public AccountType getType() {
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return type;
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}
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public void setType(AccountType type) {
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this.type = type;
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}
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public BigDecimal getBalance() {
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return balance;
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}
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public void setBalance(BigDecimal balance) {
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this.balance = balance;
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}
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}

‎_includes/v20.1/app/spring-data-jdbc/AccountRepository.java‎

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package io.roach.data.jdbc;
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import java.math.BigDecimal;
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import org.springframework.data.domain.Page;
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import org.springframework.data.jdbc.repository.query.Modifying;
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import org.springframework.data.jdbc.repository.query.Query;
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import org.springframework.data.repository.PagingAndSortingRepository;
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import org.springframework.data.repository.query.Param;
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import org.springframework.stereotype.Repository;
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import org.springframework.transaction.annotation.Transactional;
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import static org.springframework.transaction.annotation.Propagation.MANDATORY;
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/**
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* The main account repository, notice there's no implementation needed since its auto-proxied by
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* spring-data.
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* <p>
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* Should have extended PagingAndSortingRepository in normal cases.
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*/
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@Repository
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@Transactional(propagation = MANDATORY)
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public interface AccountRepository extends PagingAndSortingRepository<Account, Long> {
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@Query("SELECT * FROM account LIMIT :pageSize OFFSET :offset")
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Page<Account> findAll(@Param("pageSize") int pageSize, @Param("offset") long offset);
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@Query("SELECT count(id) FROM account")
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long countAll();
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@Query(value = "SELECT balance FROM account WHERE id=:id")
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BigDecimal getBalance(@Param("id") Long id);
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@Modifying
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@Query("UPDATE account SET balance = balance + :balance WHERE id=:id")
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void updateBalance(@Param("id") Long id, @Param("balance") BigDecimal balance);
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}

‎_includes/v20.1/app/spring-data-jdbc/AccountType.java‎

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package io.roach.data.jdbc;
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public enum AccountType {
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asset,
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expense
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}

‎_includes/v20.1/app/spring-data-jdbc/JdbcApplication.java‎

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package io.roach.data.jdbc;
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import java.math.BigDecimal;
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import java.util.ArrayDeque;
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import java.util.Deque;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.concurrent.ExecutionException;
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import java.util.concurrent.Executors;
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import java.util.concurrent.Future;
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import java.util.concurrent.ScheduledExecutorService;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import org.springframework.boot.CommandLineRunner;
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import org.springframework.boot.WebApplicationType;
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import org.springframework.boot.autoconfigure.SpringBootApplication;
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import org.springframework.boot.builder.SpringApplicationBuilder;
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import org.springframework.context.annotation.EnableAspectJAutoProxy;
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import org.springframework.core.Ordered;
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import org.springframework.data.jdbc.repository.config.EnableJdbcRepositories;
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import org.springframework.hateoas.Link;
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import org.springframework.hateoas.config.EnableHypermediaSupport;
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import org.springframework.http.HttpEntity;
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import org.springframework.http.HttpMethod;
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import org.springframework.transaction.annotation.EnableTransactionManagement;
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import org.springframework.web.client.HttpClientErrorException;
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import org.springframework.web.client.RestTemplate;
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/**
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* Spring boot server application using spring-data-jdbc for data access.
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*/
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@EnableHypermediaSupport(type = EnableHypermediaSupport.HypermediaType.HAL)
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@EnableJdbcRepositories
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@EnableAspectJAutoProxy(proxyTargetClass = true)
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@EnableSpringDataWebSupport
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@EnableTransactionManagement(order = Ordered.LOWEST_PRECEDENCE - 1) // Bump up one level to enable extra advisors
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@SpringBootApplication
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public class JdbcApplication implements CommandLineRunner {
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protected static final Logger logger = LoggerFactory.getLogger(JdbcApplication.class);
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public static void main(String[] args) {
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new SpringApplicationBuilder(JdbcApplication.class)
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.web(WebApplicationType.SERVLET)
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.run(args);
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}
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@Override
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public void run(String... args) {
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for (String a : args) {
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if ("--skip-client".equals(a)) {
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return;
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}
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}
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logger.info("Lets move some $$ around!");
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final Link transferLink = new Link("http://localhost:8080/transfer{?fromId,toId,amount}");
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final int threads = Runtime.getRuntime().availableProcessors();
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final ScheduledExecutorService executorService = Executors.newScheduledThreadPool(threads);
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Deque<Future<?>> futures = new ArrayDeque<>();
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for (int i = 0; i < threads; i++) {
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Future<?> future = executorService.submit(() -> {
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for (int j = 0; j < 100; j++) {
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int fromId = 1 + (int) Math.round(Math.random() * 3);
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int toId = fromId % 4 + 1;
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BigDecimal amount = new BigDecimal("10.00");
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Map<String, Object> form = new HashMap<>();
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form.put("fromId", fromId);
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form.put("toId", toId);
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form.put("amount", amount);
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String uri = transferLink.expand(form).getHref();
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try {
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new RestTemplate().exchange(uri, HttpMethod.POST, new HttpEntity<>(null), String.class);
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} catch (HttpClientErrorException.BadRequest e) {
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logger.warn(e.getResponseBodyAsString());
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}
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}
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});
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futures.add(future);
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}
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while (!futures.isEmpty()) {
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try {
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futures.pop().get();
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logger.info("Worker finished - {} remaining", futures.size());
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} catch (InterruptedException e) {
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Thread.currentThread().interrupt();
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} catch (ExecutionException e) {
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logger.warn("Worker failed", e.getCause());
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}
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}
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logger.info("All client workers finished but server keeps running. Have a nice day!");
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executorService.shutdownNow();
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}
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}
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