Module io.ebean.api
Package io.ebean

Class DB

java.lang.Object
io.ebean.DB
@NonNullApi public final class DB extends Object
DB is a registry of Database by name.

DB additionally provides a convenient way to use the 'default' Database.

Default database

One of the Database instances can be registered as the "default database" and can be obtained using DB.getDefault() 


 Database database = DB.getDefault();

Named database

Multiple database instances can be registered with DB and we can obtain them using DB.byName() 



 Database hrDatabase = DB.byName("hr");

Convenience methods

DB has methods like find(Class) and save(Object) which are just convenience for using the default database. 



 // fetch using the default database
 Order order = DB.find(Order.class, 10);

 // is the same as
 Database database = DB.getDefault();
 Order order = database.find(Order.class, 10);

  • Method Details

    • mock

      protected static Database mock(String name, Database server, boolean defaultServer)
      Backdoor for registering a mock implementation of Database as the default database.

    • getDefault

      public static Database getDefault()
      Return the default database.

    • byName

      public static Database byName(String name)
      Return the database for the given name.
      Parameters:
      name - The name of the database

    • script

      public static ScriptRunner script()
      Return the ScriptRunner for the default database.

      Useful to run SQL scripts that are resources. For example a test script for inserting seed data for a particular test. 

      

   DB.script().run("/scripts/test-script.sql")

    • expressionFactory

      public static ExpressionFactory expressionFactory()
      Return the ExpressionFactory from the default database.

      The ExpressionFactory is used internally by the query and ExpressionList to build the WHERE and HAVING clauses. Alternatively you can use the ExpressionFactory directly to create expressions to add to the query where clause.

      Alternatively you can use the Expr as a shortcut to the ExpressionFactory of the 'Default' database.

      You generally need to the an ExpressionFactory (or Expr) to build an expression that uses OR like Expression e = Expr.or(..., ...);

    • nextId

      public static Object nextId(Class<?> beanType)
      Return the next identity value for a given bean type.

      This will only work when a IdGenerator is on this bean type such as a DB sequence or UUID.

      For DB's supporting getGeneratedKeys and sequences such as Oracle10 you do not need to use this method generally. It is made available for more complex cases where it is useful to get an ID prior to some processing.

    • beginTransaction

      public static Transaction beginTransaction()
      Start a transaction with 'REQUIRED' semantics.

      With REQUIRED semantics if an active transaction already exists that transaction will be used.

      The transaction is stored in a ThreadLocal variable and typically you only need to use the returned Transaction IF you wish to do things like use batch mode, change the transaction isolation level, use savepoints or log comments to the transaction log.

      Example of using a transaction to span multiple calls to find(), save() etc. 

      

   try (Transaction transaction = DB.beginTransaction()) {

     Order order = DB.find(Order.class, 42);
     order.setStatus(Status.COMPLETE);
     order.save();

     transaction.commit();
   }

      If we want to externalise the transaction management then we do this via Database. With Database we can pass the transaction to the various find(), save() and execute() methods. This gives us the ability to create the transactions externally from Ebean and use the transaction explicitly via the various methods available on Database.

    • createTransaction

      public static Transaction createTransaction()
      Create a new transaction that is not held in TransactionThreadLocal.

      You will want to do this if you want multiple Transactions in a single thread or generally use transactions outside of the TransactionThreadLocal management.

    • beginTransaction

      public static Transaction beginTransaction(io.ebean.annotation.TxIsolation isolation)
      Start a transaction additionally specifying the isolation level.
      Parameters:
      isolation - the Transaction isolation level

    • beginTransaction

      public static Transaction beginTransaction(TxScope scope)
      Start a transaction typically specifying REQUIRES_NEW or REQUIRED semantics.

      Note that this provides an try finally alternative to using executeCall(TxScope, Callable) or execute(TxScope, Runnable).

      REQUIRES_NEW example:

      
 // Start a new transaction. If there is a current transaction
 // suspend it until this transaction ends

 try (Transaction txn = DB.beginTransaction(TxScope.requiresNew())) {
   ...

   // commit the transaction
   txn.commit();
 }

      REQUIRED example:

      
 // start a new transaction if there is not a current transaction

 try (Transaction txn = DB.beginTransaction(TxScope.required())) {
   ...

   // commit the transaction if it was created or
   // do nothing if there was already a current transaction
   txn.commit();
 }

    • currentTransaction

      public static Transaction currentTransaction()
      Returns the current transaction or null if there is no current transaction in scope.

    • flush

      public static void flush()
      The batch will be flushing automatically but you can use this to explicitly flush the batch if you like.

      Flushing occurs automatically when:

      • the batch size is reached
      • A query is executed on the same transaction
      • UpdateSql or CallableSql are mixed with bean save and delete
      • Transaction commit occurs
      • A getter method is called on a batched bean

    • register

      public static void register(TransactionCallback transactionCallback) throws javax.persistence.PersistenceException
      Register a TransactionCallback on the currently active transaction.

      If there is no currently active transaction then a PersistenceException is thrown.

      Parameters:
      transactionCallback - the transaction callback to be registered with the current transaction
      Throws:
      javax.persistence.PersistenceException - if there is no currently active transaction

    • commitTransaction

      public static void commitTransaction()
      Commit the current transaction.

    • rollbackTransaction

      public static void rollbackTransaction()
      Rollback the current transaction.

    • endTransaction

      public static void endTransaction()
      If the current transaction has already been committed do nothing otherwise rollback the transaction.

      It is preferable to use try with resources rather than this.

      Useful to put in a finally block to ensure the transaction is ended, rather than a rollbackTransaction() in each catch block.

      Code example: 

      
   DB.beginTransaction();
   try {
     // do some fetching and or persisting

     // commit at the end
     DB.commitTransaction();

   } finally {
     // if commit didn't occur then rollback the transaction
     DB.endTransaction();
   }

    • setRollbackOnly

      public static void setRollbackOnly()
      Mark the current transaction as rollback only.

    • diff

      public static Map<String,ValuePair> diff(Object a, Object b)
      Return a map of the differences between two objects of the same type.

      When null is passed in for b, then the 'OldValues' of a is used for the difference comparison.

    • save

      public static void save(Object bean) throws javax.persistence.OptimisticLockException
      Either Insert or Update the bean depending on its state.

      If there is no current transaction one will be created and committed for you automatically.

      Save can cascade along relationships. For this to happen you need to specify a cascade of CascadeType.ALL or CascadeType.PERSIST on the OneToMany, OneToOne or ManyToMany annotation.

      When a save cascades via a OneToMany or ManyToMany Ebean will automatically set the 'parent' object to the 'detail' object. In the example below in saving the order and cascade saving the order details the 'parent' order will be set against each order detail when it is saved.

      Throws:
      javax.persistence.OptimisticLockException

    • insert

      public static void insert(Object bean)
      Insert the bean. This is useful when you set the Id property on a bean and want to explicitly insert it.

    • insertAll

      public static void insertAll(Collection<?> beans)
      Insert a collection of beans.

    • markAsDirty

      public static void markAsDirty(Object bean) throws javax.persistence.OptimisticLockException
      Marks the entity bean as dirty.

      This is used so that when a bean that is otherwise unmodified is updated with the version property updated.

      An unmodified bean that is saved or updated is normally skipped and this marks the bean as dirty so that it is not skipped. 

      

   Customer customer = DB.find(Customer, id);

   // mark the bean as dirty so that a save() or update() will
   // increment the version property
   DB.markAsDirty(customer);
   DB.save(customer);
      Throws:
      javax.persistence.OptimisticLockException

    • update

      public static void update(Object bean) throws javax.persistence.OptimisticLockException
      Saves the bean using an update. If you know you are updating a bean then it is preferrable to use this update() method rather than save().

      Stateless updates: Note that the bean does not have to be previously fetched to call update().You can create a new instance and set some of its properties programmatically for via JSON/XML marshalling etc. This is described as a 'stateless update'.

      Optimistic Locking: Note that if the version property is not set when update() is called then no optimistic locking is performed (internally ConcurrencyMode.NONE is used). 

      

   // A 'stateless update' example
   Customer customer = new Customer();
   customer.setId(7);
   customer.setName("ModifiedNameNoOCC");
   database.update(customer);
      Throws:
      javax.persistence.OptimisticLockException

    • updateAll

      public static void updateAll(Collection<?> beans) throws javax.persistence.OptimisticLockException
      Update the beans in the collection.
      Throws:
      javax.persistence.OptimisticLockException

    • merge

      public static void merge(Object bean)
      Merge the bean using the default merge options.
      Parameters:
      bean - The bean to merge

    • merge

      public static void merge(Object bean, MergeOptions options)
      Merge the bean using the given merge options.
      Parameters:
      bean - The bean to merge
      options - The options to control the merge

    • saveAll

      public static int saveAll(Collection<?> beans) throws javax.persistence.OptimisticLockException
      Save all the beans from a Collection.
      Throws:
      javax.persistence.OptimisticLockException

    • saveAll

      public static int saveAll(Object... beans) throws javax.persistence.OptimisticLockException
      Save all the beans from a Collection.
      Throws:
      javax.persistence.OptimisticLockException

    • checkUniqueness

      public static Set<Property> checkUniqueness(Object bean)
      This method checks the uniqueness of a bean. I.e. if the save will work. It will return the properties that violates an unique / primary key. This may be done in an UI save action to validate if the user has entered correct values.

      Note: This method queries the DB for uniqueness of all indices, so do not use it in a batch update.

      Note: This checks only the root bean! 

      

   // there is a unique constraint on title

   Document doc = new Document();
   doc.setTitle("One flew over the cuckoo's nest");
   doc.setBody("clashes with doc1");

   Set<Property> properties = DB.checkUniqueness(doc);

   if (properties.isEmpty()) {
     // it is unique ... carry on

   } else {
     // build a user friendly message
     // to return message back to user

     String uniqueProperties = properties.toString();

     StringBuilder msg = new StringBuilder();

     properties.forEach((it)-> {
       Object propertyValue = it.getVal(doc);
       String propertyName = it.getName();
       msg.append(" property["+propertyName+"] value["+propertyValue+"]");
     });

     // uniqueProperties > [title]
     //       custom msg > property[title] value[One flew over the cuckoo's nest]

  }
      Parameters:
      bean - The entity bean to check uniqueness on
      Returns:
      a set of Properties if constraint validation was detected or empty list.

    • checkUniqueness

      public static Set<Property> checkUniqueness(Object bean, Transaction transaction)
      Same as checkUniqueness(Object) but with given transaction.

    • delete

      public static boolean delete(Object bean) throws javax.persistence.OptimisticLockException
      Delete the bean.

      This will return true if the bean was deleted successfully or JDBC batch is being used.

      If there is no current transaction one will be created and committed for you automatically.

      If the bean is configured with @SoftDelete then this will perform a soft delete rather than a hard/permanent delete.

      If the Bean does not have a version property (or loaded version property) and the bean does not exist then this returns false indicating that nothing was deleted. Note that, if JDBC batch mode is used then this always returns true.

      Throws:
      javax.persistence.OptimisticLockException

    • deletePermanent

      public static boolean deletePermanent(Object bean) throws javax.persistence.OptimisticLockException
      Delete the bean in permanent fashion (will not use soft delete).
      Throws:
      javax.persistence.OptimisticLockException

    • delete

      public static int delete(Class<?> beanType, Object id)
      Delete the bean given its type and id.

    • deletePermanent

      public static int deletePermanent(Class<?> beanType, Object id)
      Delete permanent the bean given its type and id.

    • deleteAll

      public static int deleteAll(Class<?> beanType, Collection<?> ids)
      Delete several beans given their type and id values.

    • deleteAllPermanent

      public static int deleteAllPermanent(Class<?> beanType, Collection<?> ids)
      Delete permanent several beans given their type and id values.

    • deleteAll

      public static int deleteAll(Collection<?> beans) throws javax.persistence.OptimisticLockException
      Delete all the beans in the Collection.
      Throws:
      javax.persistence.OptimisticLockException

    • deleteAllPermanent

      public static int deleteAllPermanent(Collection<?> beans) throws javax.persistence.OptimisticLockException
      Delete permanent all the beans in the Collection (will not use soft delete).
      Throws:
      javax.persistence.OptimisticLockException

    • refresh

      public static void refresh(Object bean)
      Refresh the values of a bean.

      Note that this resets OneToMany and ManyToMany properties so that if they are accessed a lazy load will refresh the many property.

    • refreshMany

      public static void refreshMany(Object bean, String manyPropertyName)
      Refresh a 'many' property of a bean. 
      

   Order order = ...;
   ...
   // refresh the order details...
   DB.refreshMany(order, "details");
      Parameters:
      bean - the entity bean containing the List Set or Map to refresh.
      manyPropertyName - the property name of the List Set or Map to refresh.

    • reference

      public static <T> T reference(Class<T> beanType, Object id)
      Get a reference object.

      This is sometimes described as a proxy (with lazy loading). 

      

   Product product = DB.getReference(Product.class, 1);

   // You can get the id without causing a fetch/lazy load
   Integer productId = product.getId();

   // If you try to get any other property a fetch/lazy loading will occur
   // This will cause a query to execute...
   String name = product.getName();
      Parameters:
      beanType - the type of entity bean
      id - the id value

    • sort

      public static <T> void sort(List<T> list, String sortByClause)
      Sort the list using the sortByClause which can contain a comma delimited list of property names and keywords asc, desc, nullsHigh and nullsLow.
      • asc - ascending order (which is the default)
      • desc - Descending order
      • nullsHigh - Treat null values as high/large values (which is the default)
      • nullsLow- Treat null values as low/very small values

      If you leave off any keywords the defaults are ascending order and treating nulls as high values.

      Note that the sorting uses a Comparator and Collections.sort(); and does not invoke a DB query. 

      

   // find orders and their customers
   List<Order> list = DB.find(Order.class)
     .fetch("customer")
     .order("id")
     .findList();

   // sort by customer name ascending, then by order shipDate
   // ... then by the order status descending
   DB.sort(list, "customer.name, shipDate, status desc");

   // sort by customer name descending (with nulls low)
   // ... then by the order id
   DB.sort(list, "customer.name desc nullsLow, id");
      Parameters:
      list - the list of entity beans
      sortByClause - the properties to sort the list by

    • find

      @Nullable public static <T> T find(Class<T> beanType, Object id)
      Find a bean using its unique id. This will not use caching. 
      

   // Fetch order 1
   Order order = DB.find(Order.class, 1);

      If you want more control over the query then you can use createQuery() and Query.findOne(); 

      

   // ... additionally fetching customer, customer shipping address,
   // order details, and the product associated with each order detail.
   // note: only product id and name is fetch (its a "partial object").
   // note: all other objects use "*" and have all their properties fetched.

   Query<Order> query = DB.find(Order.class)
     .setId(1)
     .fetch("customer")
     .fetch("customer.shippingAddress")
     .fetch("details")
     .query();

   // fetch associated products but only fetch their product id and name
   query.fetch("details.product", "name");

   // traverse the object graph...

   Order order = query.findOne();

   Customer customer = order.getCustomer();
   Address shippingAddress = customer.getShippingAddress();
   List<OrderDetail> details = order.getDetails();
   OrderDetail detail0 = details.get(0);
   Product product = detail0.getProduct();
   String productName = product.getName();
      Parameters:
      beanType - the type of entity bean to fetch
      id - the id value

    • sqlQuery

      public static SqlQuery sqlQuery(String sql)
      Look to execute a native sql query that does not return beans but instead returns SqlRow or uses RowMapper.

      Refer to DtoQuery for native sql queries returning DTO beans.

      Refer to findNative(Class, String) for native sql queries returning entity beans.

    • sqlUpdate

      public static SqlUpdate sqlUpdate(String sql)
      Look to execute a native sql insert update or delete statement.

      Use this to execute a Insert Update or Delete statement. The statement will be native to the database and contain database table and column names.

      See SqlUpdate for example usage.

      Returns:
      The SqlUpdate instance to set parameters and execute

    • createCallableSql

      public static CallableSql createCallableSql(String sql)
      Create a CallableSql to execute a given stored procedure.
      See Also:

    • createUpdate

      public static <T> Update<T> createUpdate(Class<T> beanType, String ormUpdate)
      Create a orm update where you will supply the insert/update or delete statement (rather than using a named one that is already defined using the @NamedUpdates annotation).

      The orm update differs from the sql update in that it you can use the bean name and bean property names rather than table and column names.

      An example: 

      

   // The bean name and properties - "topic","postCount" and "id"

   // will be converted into their associated table and column names
   String updStatement = "update topic set postCount = :pc where id = :id";

   Update<Topic> update = DB.createUpdate(Topic.class, updStatement);

   update.set("pc", 9);
   update.set("id", 3);

   int rows = update.execute();
   System.out.println("rows updated:" + rows);

    • createCsvReader

      public static <T> CsvReader<T> createCsvReader(Class<T> beanType)
      Create a CsvReader for a given beanType.

    • createNamedQuery

      public static <T> Query<T> createNamedQuery(Class<T> beanType, String namedQuery)
      Create a named query.

      For RawSql the named query is expected to be in ebean.xml.

      Type Parameters:
      T - The type of entity bean
      Parameters:
      beanType - The type of entity bean
      namedQuery - The name of the query
      Returns:
      The query

    • createQuery

      public static <T> Query<T> createQuery(Class<T> beanType)
      Create a query for a type of entity bean.

      You can use the methods on the Query object to specify fetch paths, predicates, order by, limits etc.

      You then use findList(), findSet(), findMap() and findOne() to execute the query and return the collection or bean.

      Note that a query executed by Query.findList() etc will execute against the same database from which is was created.

      Parameters:
      beanType - the class of entity to be fetched
      Returns:
      A ORM Query for this beanType

    • createQuery

      public static <T> Query<T> createQuery(Class<T> beanType, String eql)
      Parse the Ebean query language statement returning the query which can then be modified (add expressions, change order by clause, change maxRows, change fetch and select paths etc).

      Example

      

   // Find order additionally fetching the customer, details and details.product name.

   String eql = "fetch customer fetch details fetch details.product (name) where id = :orderId ";

   Query<Order> query = DB.createQuery(Order.class, eql);
   query.setParameter("orderId", 2);

   Order order = query.findOne();

   // This is the same as:

   Order order = DB.find(Order.class)
     .fetch("customer")
     .fetch("details")
     .fetch("detail.product", "name")
     .setId(2)
     .findOne();
      Type Parameters:
      T - The type of the entity bean
      Parameters:
      beanType - The type of bean to fetch
      eql - The Ebean query
      Returns:
      The query with expressions defined as per the parsed query statement

    • find

      public static <T> Query<T> find(Class<T> beanType)
      Create a query for a type of entity bean.

      This is actually the same as createQuery(Class). The reason it exists is that people used to JPA will probably be looking for a createQuery method (the same as entityManager).

      Parameters:
      beanType - the type of entity bean to find
      Returns:
      A ORM Query object for this beanType

    • findNative

      public static <T> Query<T> findNative(Class<T> beanType, String nativeSql)
      Create a query using native SQL.

      The native SQL can contain named parameters or positioned parameters. 

      

   String sql = "select c.id, c.name from customer c where c.name like ? order by c.name";

   Query<Customer> query = database.findNative(Customer.class, sql);
   query.setParameter(1, "Rob%");

   List<Customer> customers = query.findList();
      Parameters:
      beanType - The type of entity bean to fetch
      nativeSql - The SQL that can contain named or positioned parameters
      Returns:
      The query to set parameters and execute

    • findDto

      public static <T> DtoQuery<T> findDto(Class<T> dtoType, String sql)
      Create a Query for DTO beans.

      DTO beans are just normal bean like classes with public constructor(s) and setters. They do not need to be registered with Ebean before use.

      Type Parameters:
      T - The type of the DTO bean.
      Parameters:
      dtoType - The type of the DTO bean the rows will be mapped into.
      sql - The SQL query to execute.

    • update

      public static <T> UpdateQuery<T> update(Class<T> beanType)
      Create an Update query to perform a bulk update. 

      

  int rows = DB.update(Customer.class)
      .set("status", Customer.Status.ACTIVE)
      .set("updtime", new Timestamp(System.currentTimeMillis()))
      .where()
        .gt("id", 1000)
        .update();
      Type Parameters:
      T - The type of entity bean
      Parameters:
      beanType - The type of entity bean to update
      Returns:
      The update query to use

    • filter

      public static <T> Filter<T> filter(Class<T> beanType)
      Create a filter for sorting and filtering lists of entities locally without going back to the database.

      This produces and returns a new list with the sort and filters applied.

      Refer to Filter for an example of its use.

    • execute

      public static void execute(TxScope scope, Runnable r)
      Execute a TxRunnable in a Transaction with an explicit scope.

      The scope can control the transaction type, isolation and rollback semantics. 

      

 // set specific transactional scope settings
 TxScope scope = TxScope.requiresNew().setIsolation(TxIsolation.SERIALIZABLE);

 DB.execute(scope, new TxRunnable() {
   public void run() {
 	   User u1 = DB.find(User.class, 1);
     ...
   }
 });

    • execute

      public static void execute(Runnable r)
      Execute a Runnable in a Transaction with the default scope.

      The default scope runs with REQUIRED and by default will rollback on any exception (checked or runtime). 

      

 DB.execute(() -> {

   User u1 = DB.find(User.class, 1);
   User u2 = DB.find(User.class, 2);

   u1.setName("u1 mod");
   u2.setName("u2 mod");

   DB.save(u1);
   DB.save(u2);
 });

    • executeCall

      public static <T> T executeCall(TxScope scope, Callable<T> c)
      Execute a Callable in a Transaction with an explicit scope.

      The scope can control the transaction type, isolation and rollback semantics. 

      

 // set specific transactional scope settings
 TxScope scope = TxScope.requiresNew().setIsolation(TxIsolation.SERIALIZABLE);

 DB.executeCall(scope, new Callable<String>() {
   public String call() {
 	   User u1 = DB.find(User.class, 1);
 		 ...
 		 return u1.getEmail();
   }
 });

    • executeCall

      public static <T> T executeCall(Callable<T> c)
      Execute a Callable in a Transaction with the default scope.

      The default scope runs with REQUIRED and by default will rollback on any exception (checked or runtime).

      This is basically the same as TxRunnable except that it returns an Object (and you specify the return type via generics). 

      

 DB.executeCall(() -> {

   User u1 = DB.find(User.class, 1);
   User u2 = DB.find(User.class, 2);

   u1.setName("u1 mod");
   u2.setName("u2 mod");

   DB.save(u1);
   DB.save(u2);

   return u1.getEmail();
 });

    • externalModification

      public static void externalModification(String tableName, boolean inserts, boolean updates, boolean deletes)
      Inform Ebean that tables have been modified externally. These could be the result of from calling a stored procedure, other JDBC calls or external programs including other frameworks.

      If you use DB.execute(UpdateSql) then the table modification information is automatically deduced and you do not need to call this method yourself.

      This information is used to invalidate objects out of the cache and potentially text indexes. This information is also automatically broadcast across the cluster.

      If there is a transaction then this information is placed into the current transactions event information. When the transaction is committed this information is registered (with the transaction manager). If this transaction is rolled back then none of the transaction event information registers including the information you put in via this method.

      If there is NO current transaction when you call this method then this information is registered immediately (with the transaction manager).

      Parameters:
      tableName - the name of the table that was modified
      inserts - true if rows where inserted into the table
      updates - true if rows on the table where updated
      deletes - true if rows on the table where deleted

    • beanState

      public static BeanState beanState(Object bean)
      Return the BeanState for a given entity bean.

      This will return null if the bean is not an enhanced entity bean.

    • beanId

      public static Object beanId(Object bean)
      Return the value of the Id property for a given bean.

    • lock

      public static void lock(Object bean)
      Load and lock the bean using select for update.

      This should be executed inside a transaction.

      The bean needs to have an ID property set and can be a reference bean (only has ID) or partially or fully populated bean. This will load all the properties of the bean from the database using select for update.

      Parameters:
      bean - The entity bean that we wish to obtain a database lock on.

    • cacheManager

      public static ServerCacheManager cacheManager()
      Return the manager of the level 2 cache ("L2" cache).

    • backgroundExecutor

      public static BackgroundExecutor backgroundExecutor()
      Return the BackgroundExecutor service for asynchronous processing of queries.

    • json

      public static JsonContext json()
      Return the JsonContext for reading/writing JSON.

    • truncate

      public static void truncate(Class<?>... types)
      Truncate the base tables for the given bean types.

    • truncate

      public static void truncate(String... tables)
      Truncate the given tables.