Package org.apache.avro

Class Schema

java.lang.Object
org.apache.avro.JsonProperties
org.apache.avro.Schema
All Implemented Interfaces:
Serializable
public abstract class Schema extends JsonProperties implements Serializable
An abstract data type.

A schema may be one of:

  • A record, mapping field names to field value data;
  • An enum, containing one of a small set of symbols;
  • An array of values, all of the same schema;
  • A map, containing string/value pairs, of a declared schema;
  • A union of other schemas;
  • A fixed sized binary object;
  • A unicode string;
  • A sequence of bytes;
  • A 32-bit signed int;
  • A 64-bit signed long;
  • A 32-bit IEEE single-float; or
  • A 64-bit IEEE double-float; or
  • A boolean; or
  • null.
Construct a schema using one of its static createXXX methods, or more conveniently using SchemaBuilder. The schema objects are logically immutable. There are only two mutating methods - setFields(List) and addProp(String, String). The following restrictions apply on these two methods.
  • setFields(List), can be called at most once. This method exists in order to enable clients to build recursive schemas.
  • addProp(String, String) can be called with property names that are not present already. It is not possible to change or delete an existing property.
See Also:

  • Method Details

    • writeReplace

      protected Object writeReplace()

    • create

      public static Schema create(Schema.Type type)
      Create a schema for a primitive type.

    • addProp

      public void addProp(String name, String value)
      Description copied from class: JsonProperties
      Adds a property with the given name name and value value. Neither name nor value can be null. It is illegal to add a property if another with the same name but different value already exists in this schema.
      Overrides:
      addProp in class JsonProperties
      Parameters:
      name - The name of the property to add
      value - The value for the property to add

    • addProp

      public void addProp(String name, Object value)
      Overrides:
      addProp in class JsonProperties

    • getLogicalType

      public LogicalType getLogicalType()

    • createRecord

      @Deprecated public static Schema createRecord(List<Schema.Field> fields)
      Deprecated.
      This method allows to create Schema objects that cannot be parsed by SchemaParser.parse(CharSequence). It will be removed in a future version of Avro. Better use createRecord(String, String, String, boolean, List) to produce a fully qualified Schema.
      Create an anonymous record schema.

    • createRecord

      public static Schema createRecord(String name, String doc, String namespace, boolean isError)
      Create a named record schema.

    • createRecord

      public static Schema createRecord(String name, String doc, String namespace, boolean isError, List<Schema.Field> fields)
      Create a named record schema with fields already set.

    • createEnum

      public static Schema createEnum(String name, String doc, String namespace, List<String> values)
      Create an enum schema.

    • createEnum

      public static Schema createEnum(String name, String doc, String namespace, List<String> values, String enumDefault)
      Create an enum schema.

    • createArray

      public static Schema createArray(Schema elementType)
      Create an array schema.

    • createMap

      public static Schema createMap(Schema valueType)
      Create a map schema.

    • createUnion

      public static Schema createUnion(List<Schema> types)
      Create a union schema.

    • createUnion

      public static Schema createUnion(Schema... types)
      Create a union schema.

    • createFixed

      public static Schema createFixed(String name, String doc, String space, int size)
      Create a fixed schema.

    • getType

      public Schema.Type getType()
      Return the type of this schema.

    • getField

      public Schema.Field getField(String fieldName)
      If this is a record, returns the Field with the given name fieldName. If there is no field by that name, a null is returned.

    • getFields

      public List<Schema.Field> getFields()
      If this is a record, returns the fields in it. The returned list is in the order of their positions.

    • hasFields

      public boolean hasFields()
      If this is a record, returns whether the fields have been set.

    • setFields

      public void setFields(List<Schema.Field> fields)
      If this is a record, set its fields. The fields can be set only once in a schema.

    • getEnumSymbols

      public List<String> getEnumSymbols()
      If this is an enum, return its symbols.

    • getEnumDefault

      public String getEnumDefault()
      If this is an enum, return its default value.

    • getEnumOrdinal

      public int getEnumOrdinal(String symbol)
      If this is an enum, return a symbol's ordinal value.

    • hasEnumSymbol

      public boolean hasEnumSymbol(String symbol)
      If this is an enum, returns true if it contains given symbol.

    • getName

      public String getName()
      If this is a record, enum or fixed, returns its name, otherwise the name of the primitive type.

    • getDoc

      public String getDoc()
      If this is a record, enum, or fixed, returns its docstring, if available. Otherwise, returns null.

    • getNamespace

      public String getNamespace()
      If this is a record, enum or fixed, returns its namespace, if any.

    • getFullName

      public String getFullName()
      If this is a record, enum or fixed, returns its namespace-qualified name, otherwise returns the name of the primitive type.

    • addAlias

      public void addAlias(String alias)
      If this is a record, enum or fixed, add an alias.

    • addAlias

      public void addAlias(String alias, String space)
      If this is a record, enum or fixed, add an alias.

    • getAliases

      public Set<String> getAliases()
      If this is a record, enum or fixed, return its aliases, if any.

    • isError

      public boolean isError()
      Returns true if this record is an error type.

    • getElementType

      public Schema getElementType()
      If this is an array, returns its element type.

    • getValueType

      public Schema getValueType()
      If this is a map, returns its value type.

    • getTypes

      public List<Schema> getTypes()
      If this is a union, returns its types.

    • getIndexNamed

      public Integer getIndexNamed(String name)
      If this is a union, return the branch with the provided full name.

    • getFixedSize

      public int getFixedSize()
      If this is fixed, returns its size.

    • toString

      public String toString()

      Render this as JSON.

      This method is equivalent to: SchemaFormatter.getInstance("json").format(this)

      Overrides:
      toString in class Object

    • toString

      @Deprecated public String toString(boolean pretty)
      Deprecated.
      Use SchemaFormatter.format(Schema) instead, using the format json/pretty or json/inline
      Render this as JSON.
      Parameters:
      pretty - if true, pretty-print JSON.

    • toString

      @Deprecated public String toString(Collection<Schema> referencedSchemas, boolean pretty)
      Deprecated.
      Render this as JSON, but without inlining the referenced schemas.
      Parameters:
      referencedSchemas - referenced schemas
      pretty - if true, pretty-print JSON.

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • hashCode

      public final int hashCode()
      Overrides:
      hashCode in class Object

    • isUnion

      public boolean isUnion()
      Returns true if this record is a union type.

    • isNullable

      public boolean isNullable()
      Returns true if this record is a union type containing null.

    • parse

      @Deprecated public static Schema parse(File file) throws IOException
      Deprecated.
      use SchemaParser instead.
      Constructs a Schema object from JSON schema file file. The contents of file is expected to be in UTF-8 format.
      Parameters:
      file - The file to read the schema from.
      Returns:
      The freshly built Schema.
      Throws:
      IOException - if there was trouble reading the contents, or they are invalid

    • parse

      @Deprecated public static Schema parse(InputStream in) throws IOException
      Deprecated.
      use SchemaParser instead.
      Constructs a Schema object from JSON schema stream in. The contents of in is expected to be in UTF-8 format.
      Parameters:
      in - The input stream to read the schema from.
      Returns:
      The freshly built Schema.
      Throws:
      IOException - if there was trouble reading the contents, or they are invalid

    • parse

      @Deprecated public static Schema parse(String jsonSchema)
      Deprecated.
      use SchemaParser instead.
      Construct a schema from JSON text.

    • parse

      @Deprecated public static Schema parse(String jsonSchema, boolean validate)
      Deprecated.
      use SchemaParser instead.
      Construct a schema from JSON text.
      Parameters:
      validate - true if names should be validated, false if not.

    • setNameValidator

      @Deprecated public static void setNameValidator(NameValidator validator)
      Deprecated.

    • getNameValidator

      @Deprecated public static NameValidator getNameValidator()
      Deprecated.

    • setValidateDefaults

      @Deprecated public static void setValidateDefaults(boolean validateDefaults)
      Deprecated.

    • getValidateDefaults

      @Deprecated public static boolean getValidateDefaults()
      Deprecated.

    • isValidDefault

      public boolean isValidDefault(com.fasterxml.jackson.databind.JsonNode jsonValue)
      Checks if a JSON value matches the schema.
      Parameters:
      jsonValue - a value to check against the schema
      Returns:
      true if the value is valid according to this schema

    • parseJsonToObject

      public static Object parseJsonToObject(String s)
      Parses the specified json string to an object.

    • applyAliases

      public static Schema applyAliases(Schema writer, Schema reader)
      Rewrite a writer's schema using the aliases from a reader's schema. This permits reading records, enums and fixed schemas whose names have changed, and records whose field names have changed. The returned schema always contains the same data elements in the same order, but with possibly different names.