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

            
                
     
      com.sleepycat
                 
     
      je
                 
                 
     
      6.4.9
             
    

如果是5以上的版本，则需要添加oracle的仓库

            
                 
      
       oracleReleases
                  
      
       Oracle Released Java Packages
                  
      
       http://download.oracle.com/maven
                  
      
       default
              
         
    

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. */@Entitypublic 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
    
      emailAddresses = new HashSet
     
      ();    @SecondaryKey(relate = MANY_TO_MANY,            relatedEntity = Employer.class,            onRelatedEntityDelete = NULLIFY)    Set
      
        employerIds = new HashSet
       
        ();    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
        
          getEmailAddresses() {        return emailAddresses;    }    public void setEmailAddresses(Set
         
           emailAddresses) { this.emailAddresses = emailAddresses; } public Set
          
            getEmployerIds() { return employerIds; } public void setEmployerIds(Set
           
             employerIds) { this.employerIds = employerIds; }}
           
          
         
        
       
      
     
    

• 内嵌对象

/* A persistent class used in other classes. */@Persistentpublic 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

@Entitypublic 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
    
      inventoryBySku;    private PrimaryIndex
     
       vendorByName;    private SecondaryIndex
      
        inventoryByName;    /* Employer accessors */    PrimaryIndex
       
         employerById;    SecondaryIndex
        
          employerByName;    /* Person accessors */    PrimaryIndex
         
           personBySsn; SecondaryIndex
          
            personByParentSsn; SecondaryIndex
           
             personByEmailAddresses; SecondaryIndex
            
              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
    
      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
     
       inventoryBySku = store.getPrimaryIndex(                String.class, Inventory.class);        List
      
        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
    
      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
     
       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
    
      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
    
      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
     
       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
      
        employers = employerById.entities(null, cc);        try{            for(Employer employer : employers){                System.out.println(ToStringBuilder.reflectionToString(employer));            }        }finally{            employers.close();        }    }
      
     
    

本工程

参考