kafka SchemaBuilder 源码
kafka SchemaBuilder 代码
文件路径：/connect/api/src/main/java/org/apache/kafka/connect/data/SchemaBuilder.java
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.kafka.connect.data;
import org.apache.kafka.connect.errors.DataException;
import org.apache.kafka.connect.errors.SchemaBuilderException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
/**
* <p>
* SchemaBuilder provides a fluent API for constructing {@link Schema} objects. It allows you to set each of the
* properties for the schema and each call returns the SchemaBuilder so the calls can be chained. When nested types
* are required, use one of the predefined schemas from {@link Schema} or use a second SchemaBuilder inline.
* </p>
* <p>
* Here is an example of building a struct schema:
* <pre>
* Schema dateSchema = SchemaBuilder.struct()
* .name("com.example.CalendarDate").version(2).doc("A calendar date including month, day, and year.")
* .field("month", Schema.STRING_SCHEMA)
* .field("day", Schema.INT8_SCHEMA)
* .field("year", Schema.INT16_SCHEMA)
* .build();
* </pre>
* </p>
* <p>
* Here is an example of using a second SchemaBuilder to construct complex, nested types:
* <pre>
* Schema userListSchema = SchemaBuilder.array(
* SchemaBuilder.struct().name("com.example.User").field("username", Schema.STRING_SCHEMA).field("id", Schema.INT64_SCHEMA).build()
* ).build();
* </pre>
* </p>
*/
public class SchemaBuilder implements Schema {
private static final String TYPE_FIELD = "type";
private static final String OPTIONAL_FIELD = "optional";
private static final String DEFAULT_FIELD = "default";
private static final String NAME_FIELD = "name";
private static final String VERSION_FIELD = "version";
private static final String DOC_FIELD = "doc";
private final Type type;
private Boolean optional = null;
private Object defaultValue = null;
private Map<String, Field> fields = null;
private Schema keySchema = null;
private Schema valueSchema = null;
private String name;
private Integer version;
// Optional human readable documentation describing this schema.
private String doc;
// Additional parameters for logical types.
private Map<String, String> parameters;
public SchemaBuilder(Type type) {
if (null == type)
throw new SchemaBuilderException("type cannot be null");
this.type = type;
if (type == Type.STRUCT) {
fields = new LinkedHashMap<>();
}
}
// Common/metadata fields
@Override
public boolean isOptional() {
return optional == null ? false : optional;
}
/**
* Set this schema as optional.
* @return the SchemaBuilder
*/
public SchemaBuilder optional() {
checkCanSet(OPTIONAL_FIELD, optional, true);
optional = true;
return this;
}
/**
* Set this schema as required. This is the default, but this method can be used to make this choice explicit.
* @return the SchemaBuilder
*/
public SchemaBuilder required() {
checkCanSet(OPTIONAL_FIELD, optional, false);
optional = false;
return this;
}
@Override
public Object defaultValue() {
return defaultValue;
}
/**
* Set the default value for this schema. The value is validated against the schema type, throwing a
* {@link SchemaBuilderException} if it does not match.
* @param value the default value
* @return the SchemaBuilder
*/
public SchemaBuilder defaultValue(Object value) {
checkCanSet(DEFAULT_FIELD, defaultValue, value);
checkNotNull(TYPE_FIELD, type, DEFAULT_FIELD);
try {
ConnectSchema.validateValue(this, value);
} catch (DataException e) {
throw new SchemaBuilderException("Invalid default value", e);
}
defaultValue = value;
return this;
}
@Override
public String name() {
return name;
}
/**
* Set the name of this schema.
* @param name the schema name
* @return the SchemaBuilder
*/
public SchemaBuilder name(String name) {
checkCanSet(NAME_FIELD, this.name, name);
this.name = name;
return this;
}
@Override
public Integer version() {
return version;
}
/**
* Set the version of this schema. Schema versions are integers which, if provided, must indicate which schema is
* newer and which is older by their ordering.
* @param version the schema version
* @return the SchemaBuilder
*/
public SchemaBuilder version(Integer version) {
checkCanSet(VERSION_FIELD, this.version, version);
this.version = version;
return this;
}
@Override
public String doc() {
return doc;
}
/**
* Set the documentation for this schema.
* @param doc the documentation
* @return the SchemaBuilder
*/
public SchemaBuilder doc(String doc) {
checkCanSet(DOC_FIELD, this.doc, doc);
this.doc = doc;
return this;
}
@Override
public Map<String, String> parameters() {
return parameters == null ? null : Collections.unmodifiableMap(parameters);
}
/**
* Set a schema parameter.
* @param propertyName name of the schema property to define
* @param propertyValue value of the schema property to define, as a String
* @return the SchemaBuilder
*/
public SchemaBuilder parameter(String propertyName, String propertyValue) {
// Preserve order of insertion with a LinkedHashMap. This isn't strictly necessary, but is nice if logical types
// can print their properties in a consistent order.
if (parameters == null)
parameters = new LinkedHashMap<>();
parameters.put(propertyName, propertyValue);
return this;
}
/**
* Set schema parameters. This operation is additive; it does not remove existing parameters that do not appear in
* the set of properties pass to this method.
* @param props Map of properties to set
* @return the SchemaBuilder
*/
public SchemaBuilder parameters(Map<String, String> props) {
// Avoid creating an empty set of properties so we never have an empty map
if (props.isEmpty())
return this;
if (parameters == null)
parameters = new LinkedHashMap<>();
parameters.putAll(props);
return this;
}
@Override
public Type type() {
return type;
}
/**
* Create a SchemaBuilder for the specified type.
*
* Usually it will be simpler to use one of the variants like {@link #string()} or {@link #struct()}, but this form
* can be useful when generating schemas dynamically.
*
* @param type the schema type
* @return a new SchemaBuilder
*/
public static SchemaBuilder type(Type type) {
return new SchemaBuilder(type);
}
// Primitive types
/**
* @return a new {@link Schema.Type#INT8} SchemaBuilder
*/
public static SchemaBuilder int8() {
return new SchemaBuilder(Type.INT8);
}
/**
* @return a new {@link Schema.Type#INT16} SchemaBuilder
*/
public static SchemaBuilder int16() {
return new SchemaBuilder(Type.INT16);
}
/**
* @return a new {@link Schema.Type#INT32} SchemaBuilder
*/
public static SchemaBuilder int32() {
return new SchemaBuilder(Type.INT32);
}
/**
* @return a new {@link Schema.Type#INT64} SchemaBuilder
*/
public static SchemaBuilder int64() {
return new SchemaBuilder(Type.INT64);
}
/**
* @return a new {@link Schema.Type#FLOAT32} SchemaBuilder
*/
public static SchemaBuilder float32() {
return new SchemaBuilder(Type.FLOAT32);
}
/**
* @return a new {@link Schema.Type#FLOAT64} SchemaBuilder
*/
public static SchemaBuilder float64() {
return new SchemaBuilder(Type.FLOAT64);
}
/**
* @return a new {@link Schema.Type#BOOLEAN} SchemaBuilder
*/
public static SchemaBuilder bool() {
return new SchemaBuilder(Type.BOOLEAN);
}
/**
* @return a new {@link Schema.Type#STRING} SchemaBuilder
*/
public static SchemaBuilder string() {
return new SchemaBuilder(Type.STRING);
}
/**
* @return a new {@link Schema.Type#BYTES} SchemaBuilder
*/
public static SchemaBuilder bytes() {
return new SchemaBuilder(Type.BYTES);
}
// Structs
/**
* @return a new {@link Schema.Type#STRUCT} SchemaBuilder
*/
public static SchemaBuilder struct() {
return new SchemaBuilder(Type.STRUCT);
}
/**
* Add a field to this struct schema. Throws a SchemaBuilderException if this is not a struct schema.
* @param fieldName the name of the field to add
* @param fieldSchema the Schema for the field's value
* @return the SchemaBuilder
*/
public SchemaBuilder field(String fieldName, Schema fieldSchema) {
if (type != Type.STRUCT)
throw new SchemaBuilderException("Cannot create fields on type " + type);
if (null == fieldName || fieldName.isEmpty())
throw new SchemaBuilderException("fieldName cannot be null.");
if (null == fieldSchema)
throw new SchemaBuilderException("fieldSchema for field " + fieldName + " cannot be null.");
int fieldIndex = fields.size();
if (fields.containsKey(fieldName))
throw new SchemaBuilderException("Cannot create field because of field name duplication " + fieldName);
fields.put(fieldName, new Field(fieldName, fieldIndex, fieldSchema));
return this;
}
/**
* Get the list of fields for this Schema. Throws a DataException if this schema is not a struct.
* @return the list of fields for this Schema
*/
@Override
public List<Field> fields() {
if (type != Type.STRUCT)
throw new DataException("Cannot list fields on non-struct type");
return new ArrayList<>(fields.values());
}
@Override
public Field field(String fieldName) {
if (type != Type.STRUCT)
throw new DataException("Cannot look up fields on non-struct type");
return fields.get(fieldName);
}
// Maps & Arrays
/**
* @param valueSchema the schema for elements of the array
* @return a new {@link Schema.Type#ARRAY} SchemaBuilder
*/
public static SchemaBuilder array(Schema valueSchema) {
if (null == valueSchema)
throw new SchemaBuilderException("valueSchema cannot be null.");
SchemaBuilder builder = new SchemaBuilder(Type.ARRAY);
builder.valueSchema = valueSchema;
return builder;
}
/**
* @param keySchema the schema for keys in the map
* @param valueSchema the schema for values in the map
* @return a new {@link Schema.Type#MAP} SchemaBuilder
*/
public static SchemaBuilder map(Schema keySchema, Schema valueSchema) {
if (null == keySchema)
throw new SchemaBuilderException("keySchema cannot be null.");
if (null == valueSchema)
throw new SchemaBuilderException("valueSchema cannot be null.");
SchemaBuilder builder = new SchemaBuilder(Type.MAP);
builder.keySchema = keySchema;
builder.valueSchema = valueSchema;
return builder;
}
static SchemaBuilder arrayOfNull() {
return new SchemaBuilder(Type.ARRAY);
}
static SchemaBuilder mapOfNull() {
return new SchemaBuilder(Type.MAP);
}
static SchemaBuilder mapWithNullKeys(Schema valueSchema) {
SchemaBuilder result = new SchemaBuilder(Type.MAP);
result.valueSchema = valueSchema;
return result;
}
static SchemaBuilder mapWithNullValues(Schema keySchema) {
SchemaBuilder result = new SchemaBuilder(Type.MAP);
result.keySchema = keySchema;
return result;
}
@Override
public Schema keySchema() {
return keySchema;
}
@Override
public Schema valueSchema() {
return valueSchema;
}
/**
* Build the Schema using the current settings
* @return the {@link Schema}
*/
public Schema build() {
return new ConnectSchema(type, isOptional(), defaultValue, name, version, doc,
parameters == null ? null : Collections.unmodifiableMap(parameters),
fields == null ? null : Collections.unmodifiableList(new ArrayList<>(fields.values())), keySchema, valueSchema);
}
/**
* Return a concrete instance of the {@link Schema} specified by this builder
* @return the {@link Schema}
*/
@Override
public Schema schema() {
return build();
}
private static void checkCanSet(String fieldName, Object fieldVal, Object val) {
if (fieldVal != null && fieldVal != val)
throw new SchemaBuilderException("Invalid SchemaBuilder call: " + fieldName + " has already been set.");
}
private static void checkNotNull(String fieldName, Object val, String fieldToSet) {
if (val == null)
throw new SchemaBuilderException("Invalid SchemaBuilder call: " + fieldName + " must be specified to set " + fieldToSet);
}
}
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