描述

SQLInput用于查询过程中把数据库中UDT类型映射成用户自定义的java类型。

java.sql.SQLInput是JDBC规范中用于读取数据库自定义类型（UDT）字段值的核心接口，它是SQLData接口的配套工具，当实现SQLData接口的Java类执行readSQL()方法时，JDBC会自动创建SQLInput实例，通过该实例的读取方法（如readInt()、readString()），按顺序读取数据库自定义类型（如STRUCT、复合类型）中的每个字段值，并赋值给Java对象的对应属性。

详细接口说明请参考JDBC官方网站 (opens new window)。

方法

java.sql.SQLInput包含的方法如下：

方法	返回类型
readString() throws SQLException	String
readNString() throws SQLException	String
readBoolean() throws SQLException	boolean
readByte() throws SQLException	byte
readShort() throws SQLException	short
readInt() throws SQLException	int
readLong() throws SQLException	long
readFloat() throws SQLException	float
readDouble() throws SQLException	double
readBigDecimal() throws SQLException	BigDecimal
readBytes() throws SQLException	byte[]
readDate() throws SQLException	Date
readTime() throws SQLException	Time
readTimestamp() throws SQLException	Timestamp
readBlob() throws SQLException	Blob
readClob() throws SQLException	Clob
readNClob() throws SQLException	NClob
readSQLXML() throws SQLException	SQLXML
readCharacterStream() throws SQLException	Reader
readAsciiStream() throws SQLException	InputStream
readBinaryStream() throws SQLException	InputStream
readObject() throws SQLException	Object
readObject(Class<T> type) throws SQLException	<T> T
readArray() throws SQLException	Array
readRowId() throws SQLException	RowId
wasNull()	boolean

示例

package quickstart;

import java.io.InputStream;
import java.io.Reader;
import java.math.BigDecimal;
import java.sql.Array;
import java.sql.Blob;
import java.sql.Clob;
import java.sql.Date;
import java.sql.NClob;
import java.sql.RowId;
import java.sql.SQLData;
import java.sql.SQLException;
import java.sql.SQLInput;
import java.sql.SQLOutput;
import java.sql.SQLXML;
import java.sql.Time;
import java.sql.Timestamp;
import java.util.Map;

// SQLData 实现示例
public class CompleteEmployee implements SQLData {
    // 基础信息
    private int employeeId;
    private String firstName;
    private String lastName;
    private String nStringName;
    private boolean active;

    // 数值类型
    private byte securityLevel;
    private short departmentCode;
    private int age;
    private long employeeNumber;
    private float bonusRate;
    private double salary;
    private BigDecimal annualBonus;

    // 二进制数据
    private byte[] photo;

    // 日期和时间
    private Date hireDate;
    private Time startTime;
    private Timestamp lastLogin;

    // 大对象
    private Blob resume;
    private Clob biography;
    private NClob multilingualBio;
    private SQLXML configXml;

    // 复杂类型
    private Array skills;
    private RowId rowId;
    private SQLData metadata;

    // Getter和Setter
    public int getEmployeeId() { return employeeId; }
    public void setEmployeeId(int id) { this.employeeId = id; }
    public String getFirstName() { return firstName; }
    public void setFirstName(String name) { this.firstName = name; }

    // SQLData接口实现
    @Override
    public String getSQLTypeName() throws SQLException {
        return "EMPLOYEE_TYPE";
    }

    @Override
    public void readSQL(SQLInput stream, String typeName) throws SQLException {
        // 1. 读取基础信息
        employeeId = stream.readInt();
        firstName = stream.readString();
        lastName = stream.readString();
        nStringName = stream.readNString();
        active = stream.readBoolean();

        // 检查NULL值
        if (stream.wasNull()) {
            active = true;
        }

        // 2. 读取数值类型
        securityLevel = stream.readByte();
        departmentCode = stream.readShort();
        age = stream.readInt();
        employeeNumber = stream.readLong();
        bonusRate = stream.readFloat();
        salary = stream.readDouble();
        annualBonus = stream.readBigDecimal();

        // 3. 读取二进制数据
        photo = stream.readBytes();

        // 4. 读取日期和时间
        hireDate = stream.readDate();
        startTime = stream.readTime();
        lastLogin = stream.readTimestamp();

        // 5. 读取大对象
        resume = stream.readBlob();
        biography = stream.readClob();
        multilingualBio = stream.readNClob();
        configXml = stream.readSQLXML();
        
        // 6. 读取流
        Reader charStream = stream.readCharacterStream();
        InputStream asciiStream = stream.readAsciiStream();
        InputStream binaryStream = stream.readBinaryStream();

        // 7. 读取对象
        Object rawObject = stream.readObject();
        if (rawObject instanceof SQLData) {
            metadata = (SQLData) rawObject;
        }

        // 使用泛型方法读取对象
        SQLData typedMetadata = stream.readObject(SQLData.class);

        // 8. 读取数组
        skills = stream.readArray();

        // 9. 读取行 ID
        rowId = stream.readRowId();

        // 最终检查
        if (stream.wasNull()) {
            System.out.println("Last read value was NULL");
        }
    }

    @Override
    public void writeSQL(SQLOutput stream) throws SQLException {
        // 写入数据到 SQLOutput
        stream.writeInt(employeeId);
        stream.writeString(firstName);
        stream.writeString(lastName);
        stream.writeNString(nStringName);
        stream.writeBoolean(active);
        stream.writeByte(securityLevel);
        stream.writeShort(departmentCode);
        stream.writeInt(age);
        stream.writeLong(employeeNumber);
        stream.writeFloat(bonusRate);
        stream.writeDouble(salary);
        stream.writeBigDecimal(annualBonus);
        stream.writeBytes(photo);
        stream.writeDate(hireDate);
        stream.writeTime(startTime);
        stream.writeTimestamp(lastLogin);
        stream.writeBlob(resume);
        stream.writeClob(biography);
        stream.writeNClob(multilingualBio);
        stream.writeSQLXML(configXml);
        stream.writeObject(metadata);
        stream.writeArray(skills);
        stream.writeRowId(rowId);
    }

    public static void main(String[] args) throws SQLException {
        CompleteEmployee employee = new CompleteEmployee();
        System.out.println(employee.getSQLTypeName());
    }
}

正常情况下，程序输出如下：

EMPLOYEE_TYPE