BerkeleyDB的Java版本的使用
序
BerkeleyDB在爬虫、搜索领域里头用的比较多，整体来讲的特点是嵌入式、kv数据库，功能强大，能支持几百T的存储。本文主要讲述怎么在java里头使用它。
添加依赖
<!-- Berkeley DB Java Edition --> <dependency> <groupId>com.sleepycat</groupId> <artifactId>je</artifactId> <!--<version>5.0.73</version>--> <version>6.4.9</version> </dependency>如果是5以上的版本，则需要添加oracle的仓库
<repositories> <repository> <id>oracleReleases</id> <name>Oracle Released Java Packages</name> <url>http://download.oracle.com/maven</url> <layout>default</layout> </repository> </repositories>使用方式
在java里头主要有两种使用方式，一种是基于注解形式的，一种是原始的api使用。本文主要是用注解形式的。
领域模型
/* An entity class. */ @Entity public class Person { @PrimaryKey String ssn; String name; Address address; @SecondaryKey(relate = MANY_TO_ONE, relatedEntity = Person.class) String parentSsn; @SecondaryKey(relate = ONE_TO_MANY) Set<String> emailAddresses = new HashSet<String>(); @SecondaryKey(relate = MANY_TO_MANY, relatedEntity = Employer.class, onRelatedEntityDelete = NULLIFY) Set<Long> employerIds = new HashSet<Long>(); public Person(String name, String ssn, String parentSsn) { this.name = name; this.ssn = ssn; this.parentSsn = parentSsn; } private Person() { } // For deserialization public String getSsn() { return ssn; } public void setSsn(String ssn) { this.ssn = ssn; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Address getAddress() { return address; } public void setAddress(Address address) { this.address = address; } public String getParentSsn() { return parentSsn; } public void setParentSsn(String parentSsn) { this.parentSsn = parentSsn; } public Set<String> getEmailAddresses() { return emailAddresses; } public void setEmailAddresses(Set<String> emailAddresses) { this.emailAddresses = emailAddresses; } public Set<Long> getEmployerIds() { return employerIds; } public void setEmployerIds(Set<Long> employerIds) { this.employerIds = employerIds; } }-
内嵌对象
/* A persistent class used in other classes. */ @Persistent public class Address { String street; String city; String state; int zipCode; public Address() { } // For deserialization public String getStreet() { return street; } public void setStreet(String street) { this.street = street; } public String getCity() { return city; } public void setCity(String city) { this.city = city; } public String getState() { return state; } public void setState(String state) { this.state = state; } public int getZipCode() { return zipCode; } public void setZipCode(int zipCode) { this.zipCode = zipCode; } }-
关联
@Entity public class Employer { @PrimaryKey(sequence = "ID") private long id; @SecondaryKey(relate = ONE_TO_ONE) private String name; private Address address; public Employer(String name) { this.name = name; } private Employer() { } // For deserialization public long getId() { return id; } public void setId(long id) { this.id = id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Address getAddress() { return address; } public void setAddress(Address address) { this.address = address; } }初始化及关闭操作
private Environment myEnv; private EntityStore store; private PrimaryIndex<String, Inventory> inventoryBySku; private PrimaryIndex<String, Vendor> vendorByName; private SecondaryIndex<String, String, Inventory> inventoryByName; /* Employer accessors */ PrimaryIndex<Long, Employer> employerById; SecondaryIndex<String, Long, Employer> employerByName; /* Person accessors */ PrimaryIndex<String, Person> personBySsn; SecondaryIndex<String, String, Person> personByParentSsn; SecondaryIndex<String, String, Person> personByEmailAddresses; SecondaryIndex<Long, String, Person> personByEmployerIds; private File envHome = new File(System.getProperty("user.dir") + File.separator + "bdb"); private boolean readOnly = false; @Before public void prepare() { EnvironmentConfig myEnvConfig = new EnvironmentConfig(); StoreConfig storeConfig = new StoreConfig(); myEnvConfig.setReadOnly(readOnly); storeConfig.setReadOnly(readOnly); // If the environment is opened for write, then we want to be // able to create the environment and entity store if // they do not exist. myEnvConfig.setAllowCreate(!readOnly); storeConfig.setAllowCreate(!readOnly); // Open the environment and entity store System.out.println(envHome.getAbsolutePath()); if (!envHome.exists()) { envHome.mkdir(); } myEnv = new Environment(envHome, myEnvConfig); store = new EntityStore(myEnv, "EntityStore", storeConfig); // Primary key for Inventory classes inventoryBySku = store.getPrimaryIndex(String.class, Inventory.class); // Secondary key for Inventory classes // Last field in the getSecondaryIndex() method must be // the name of a class member; in this case, an Inventory.class // data member. inventoryByName = store.getSecondaryIndex(inventoryBySku, String.class, "itemName"); // Primary key for Vendor class vendorByName = store.getPrimaryIndex(String.class, Vendor.class); employerById = store.getPrimaryIndex(Long.class, Employer.class); employerByName = store.getSecondaryIndex(employerById, String.class, "name"); personBySsn = store.getPrimaryIndex(String.class, Person.class); personByParentSsn = store.getSecondaryIndex(personBySsn, String.class, "parentSsn"); personByEmailAddresses = store.getSecondaryIndex(personBySsn, String.class, "emailAddresses"); personByEmployerIds = store.getSecondaryIndex(personBySsn, Long.class, "employerIds"); } @After public void close() { if (store != null) { try { store.close(); } catch (DatabaseException dbe) { dbe.printStackTrace(); } } if (myEnv != null) { try { // Finally, close the store and environment. myEnv.close(); } catch (DatabaseException dbe) { dbe.printStackTrace(); } } }增删改查
添加数据
@Test public void putData() throws IOException { List<String> readLines = Resources.readLines(this.getClass().getClassLoader().getResource("vendors.txt"), Charsets.UTF_8); for (String data : readLines) { String[] sArray = data.split("#"); Vendor theVendor = new Vendor(); theVendor.setVendorName(sArray[0]); theVendor.setAddress(sArray[1]); theVendor.setCity(sArray[2]); theVendor.setState(sArray[3]); theVendor.setZipcode(sArray[4]); theVendor.setBusinessPhoneNumber(sArray[5]); theVendor.setRepName(sArray[6]); theVendor.setRepPhoneNumber(sArray[7]); // Put it in the store. Because we do not explicitly set // a transaction here, and because the store was opened // with transactional support, auto commit is used for each // write to the store. vendorByName.put(theVendor); } // Primary key for Inventory classes PrimaryIndex<String, Inventory> inventoryBySku = store.getPrimaryIndex( String.class, Inventory.class); List<String> data = Resources.readLines(this.getClass().getClassLoader().getResource("inventory.txt"), Charsets.UTF_8); for (String row : data) { String[] sArray = row.split("#"); Inventory theInventory = new Inventory(); theInventory.setItemName(sArray[0]); theInventory.setSku(sArray[1]); theInventory.setVendorPrice((new Float(sArray[2])).floatValue()); theInventory.setVendorInventory((new Integer(sArray[3])).intValue()); theInventory.setCategory(sArray[4]); theInventory.setVendor(sArray[5]); // Put it in the store. Note that this causes our secondary key // to be automatically updated for us. inventoryBySku.put(theInventory); } }查询数据
@Test public void getInventoryData() { // Use the inventory name secondary key to retrieve // these objects. EntityCursor<Inventory> items = inventoryByName.subIndex("Oranges").entities(); try { for (Inventory item : items) { System.out.println(ToStringBuilder.reflectionToString(item)); } } finally { items.close(); } } @Test public void getAllInventory() { // Get a cursor that will walk every // inventory object in the store. EntityCursor<Inventory> items = inventoryBySku.entities(); try { for (Inventory item : items) { System.out.println(ToStringBuilder.reflectionToString(item)); } } finally { items.close(); } }更新
如果不开启允许重复记录的话，put就是更新
@Test public void update() { String pk = "apple-for-update"; Inventory theInventory = new Inventory(); theInventory.setItemName("Apples"); theInventory.setSku(pk); theInventory.setVendorPrice(1.20f); theInventory.setVendorInventory(728); theInventory.setCategory("fruits"); theInventory.setVendor("Off the Vine"); inventoryBySku.put(theInventory); Inventory inventory = inventoryBySku.get(pk); System.out.println(ToStringBuilder.reflectionToString(inventory)); inventory.setVendor("vendor update"); inventoryBySku.put(inventory); System.out.println(ToStringBuilder.reflectionToString(inventoryBySku.get(pk))); }删除
@Test public void delete() { String pk = "apple-for-update"; Inventory theInventory = new Inventory(); theInventory.setItemName("Apples"); theInventory.setSku(pk); theInventory.setVendorPrice(1.20f); theInventory.setVendorInventory(728); theInventory.setCategory("fruits"); theInventory.setVendor("Off the Vine"); inventoryBySku.put(theInventory); Inventory inventory = inventoryBySku.get(pk); System.out.println(ToStringBuilder.reflectionToString(inventory)); boolean rs = inventoryBySku.delete(pk); Assert.assertTrue(rs); Assert.assertNull(inventoryBySku.get(pk)); }统计
@Test public void count(){ EntityCursor<Employer> cursor = null; try{ cursor = employerById.entities(); int count = -1; if(cursor.next() != null){ count = cursor.count(); } System.out.println("employee count:" + count); }finally { if(cursor != null){ cursor.close(); } } }级联及主键自增情况
@Test public void sequencePk() { /* * Add a parent and two children using the Person primary index. * Specifying a non-null parentSsn adds the child Person to the * sub-index of children for that parent key. */ personBySsn.put(new Person("Bob Smith", "111-11-1111", null)); personBySsn.put(new Person("Mary Smith", "333-33-3333", "111-11-1111")); personBySsn.put(new Person("Jack Smith", "222-22-2222", "111-11-1111")); /* Print the children of a parent using a sub-index and a cursor. */ EntityCursor<Person> children = personByParentSsn.subIndex("111-11-1111").entities(); try { for (Person child : children) { System.out.println(child.getSsn() + ' ' + child.getName()); } } finally { children.close(); } /* Get Bob by primary key using the primary index. */ Person bob = personBySsn.get("111-11-1111"); Assert.assertNotNull(bob); /* * Create two employers if they do not already exist. Their primary * keys are assigned from a sequence. */ Employer gizmoInc = employerByName.get("Gizmo Inc"); if (gizmoInc == null) { gizmoInc = new Employer("Gizmo Inc"); employerById.put(gizmoInc); } Employer gadgetInc = employerByName.get("Gadget Inc"); if (gadgetInc == null) { gadgetInc = new Employer("Gadget Inc"); employerById.put(gadgetInc); } /* Bob has two jobs and two email addresses. */ bob.getEmployerIds().add(gizmoInc.getId()); bob.getEmployerIds().add(gadgetInc.getId()); bob.getEmailAddresses().add("bob@bob.com"); bob.getEmailAddresses().add("bob@gmail.com"); /* Update Bob's record. */ personBySsn.put(bob); /* Bob can now be found by both email addresses. */ bob = personByEmailAddresses.get("bob@bob.com"); Assert.assertNotNull(bob); bob = personByEmailAddresses.get("bob@gmail.com"); Assert.assertNotNull(bob); /* Bob can also be found as an employee of both employers. */ EntityIndex<String, Person> employees; employees = personByEmployerIds.subIndex(gizmoInc.getId()); Assert.assertTrue( employees.contains("111-11-1111")); employees = personByEmployerIds.subIndex(gadgetInc.getId()); Assert.assertTrue(employees.contains("111-11-1111")); /* * When an employer is deleted, the onRelatedEntityDelete=NULLIFY for * the employerIds key causes the deleted ID to be removed from Bob's * employerIds. */ employerById.delete(gizmoInc.getId()); bob = personBySsn.get("111-11-1111"); Assert.assertNotNull(bob); Assert.assertFalse(bob.getEmployerIds().contains(gizmoInc.getId())); } @Test public void cursor() { CursorConfig cc = new CursorConfig(); // This is ignored if the store is not opened with uncommitted read // support. cc.setReadUncommitted(true); EntityCursor<Employer> employers = employerById.entities(null, cc); try{ for(Employer employer : employers){ System.out.println(ToStringBuilder.reflectionToString(employer)); } }finally{ employers.close(); } }本工程 github
参考
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Oracle Berkeley DB Java Edition, 12c Release 1
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