[英]UTF-8 issue when using hibernate to store/retrieve JSON data from MySql
[英]Store/Retrieve Json data to/from Mysql 5.7 database using hibernate
我將開始一個需要生成動態Google表單的項目。 該項目的要求是我需要使用mysql 5.7,以便可以使用json數據類型存儲/檢索json數據。 我對此很好。 我知道,可以使用HQL。 但是我不知道是如何使用對象關系映射在Hibernate中實現它的?
有任何想法嗎 ?
提前致謝 !
最近,我已經解決了類似的任務。 我想為時已晚,但是也許有人覺得這很有用。
簡短的回答 :您應該創建必須實現org.hibernate.usertype.UserType接口的類(例如“ com.test.MyJsonType ”),在該接口中nullSafeGet方法應將JSON反序列化為Java對象(使用Jackson), nullSafeSet將POJO序列化為JSON和其他一些輔助方法。
然后,您應該擴展MySQLDialect並注冊新的列類型“ json”。
最后,您可以通過@Type(type =“ com.test.MyJsonType ”)注釋實體字段,該實體字段應映射到MySQL json列。
如果您不想用包名寫類型,也可以在這里閱讀有關@TypeDef的信息 。
例如:
public class MyJsonType implements UserType {
@Override
public int[] sqlTypes() {
return new int[] { Types.VARCHAR };
}
@Override
public Class<Characteristics> returnedClass() {
return Characteristics.class;
}
@Override
public Object nullSafeGet(final ResultSet rs, final String[] names, final SessionImplementor session, final Object owner)
throws HibernateException, SQLException {
final String cellContent = rs.getString(names[0]);
if (cellContent == null) {
return null;
}
try {
final ObjectMapper mapper = new ObjectMapper().configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
return mapper.readValue(cellContent.getBytes("UTF-8"), returnedClass());
} catch (final Exception ex) {
throw new RuntimeException("Failed to convert String to Invoice: " + ex.getMessage(), ex);
}
}
@Override
public void nullSafeSet(final PreparedStatement ps, final Object value, final int idx, final SessionImplementor session)
throws HibernateException, SQLException {
if (value == null) {
ps.setNull(idx, Types.VARCHAR);
return;
}
try {
final ObjectMapper mapper = new ObjectMapper();
final StringWriter w = new StringWriter();
mapper.writeValue(w, value);
w.flush();
ps.setObject(idx, w.toString(), Types.VARCHAR);
} catch (final Exception ex) {
throw new RuntimeException("Failed to convert Invoice to String: " + ex.getMessage(), ex);
}
}
@Override
public Object deepCopy(final Object value) throws HibernateException {
try {
ByteArrayOutputStream bos = new ByteArrayOutputStream();
ObjectOutputStream oos = new ObjectOutputStream(bos);
oos.writeObject(value);
oos.flush();
oos.close();
bos.close();
ByteArrayInputStream bais = new ByteArrayInputStream(bos.toByteArray());
return new ObjectInputStream(bais).readObject();
} catch (ClassNotFoundException | IOException ex) {
throw new HibernateException(ex);
}
}
@Override
public boolean isMutable() {
return true;
}
@Override
public Serializable disassemble(final Object value) throws HibernateException {
return (Serializable) this.deepCopy(value);
}
@Override
public Object assemble(final Serializable cached, final Object owner) throws HibernateException {
return this.deepCopy(cached);
}
@Override
public Object replace(final Object original, final Object target, final Object owner) throws HibernateException {
return this.deepCopy(original);
}
@Override
public boolean equals(Object x, Object y) throws HibernateException {
return Objects.equals(x, y);
}
@Override
public int hashCode(Object x) throws HibernateException {
return Objects.hashCode(x);
}
}
POJO類:
public class Characteristics implements Serializable {
private String field;
public String getField() {
return field;
}
public void setField(String field) {
this.field= field;
}
@Override
public boolean equals(Object obj) {
if (obj == null) return false;
if (getClass() != obj.getClass()) return false;
final Characteristics other = (Characteristics) obj;
return Objects.equals(this.field, other.field);
}
@Override
public int hashCode() {
return Objects.hash(this.field);
}
}
注冊新的列類型:
public class JsonMySQLDialect extends MySQLDialect {
public JsonMySQLDialect() {
this.registerColumnType(Types.VARCHAR, "json");
}
}
使用方法:
@Entity
@Table(name = "Table")
public class TableClass {
...
@Column
@Type(type = "com.test.MyJsonType")
protected Characteristics characteristics;
...
}
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