SpringDataJPA中出现的保存出现的Caused by: org.hibernate.PersistentObjectException: detached entity passed to persist:

出现这种问题是先看看自己的实体类主键策略

通常原因分两种：

1.@GeneratedValue(strategy=GenerationType.IDENTITY)

    这种主键策略是自增长，数据库中设置主键自增和在对应的实体类中设置对应的主键自增，只要有哪一边没有设置，就会报该异常

2.我的数据表主键不是自增长，如图

这是我自己写的主键生成策略

*主键生成工具类

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class PrimaryKeyAlgorithmUtil {

    private static final long ONE_STEP = 10;
    private static final Lock LOCK = new ReentrantLock();
    private static long lastTime = System.currentTimeMillis();
    private static short lastCount = 0;
    private static int count = 0;

    @SuppressWarnings("finally")
    public static Long nextId()
    {
        LOCK.lock();
        try {
            if (lastCount == ONE_STEP) {
                boolean done = false;
                while (!done) {
                    long now = System.currentTimeMillis();
                    if (now == lastTime) {
                        try {
                            Thread.currentThread();
                            Thread.sleep(1);
                        } catch (java.lang.InterruptedException e) {
                        }
                        continue;
                    } else {
                        lastTime = now;
                        lastCount = 0;
                        done = true;
                    }
                }
            }
            count = lastCount++;
        }
        finally
        {
            LOCK.unlock();
            return Long.parseLong(lastTime+""+String.format("%03d",count));
        }
    }
}

*主键生成器

import org.hibernate.MappingException;
import org.hibernate.engine.spi.SharedSessionContractImplementor;
import java.io.Serializable;

public class PrimaryKeyGenerator  extends IdentityGenerator {

    @Override
    public Serializable generate(SharedSessionContractImplementor session, Object object) throws MappingException {
        Object id = PrimaryKeyAlgorithmUtil.nextId();
        if (id != null) {
            return (Serializable) id;
        }
        return super.generate(session, object);
    }
*实体类




上图权限类和用户类为多对多的对应关系 现要插入一个，用户有多个权限

当项目启动后调这个方法会出现异常

这是因为数据表主键没有设置自增长，实体类也没设置id数据无法保存
只需要给实体setId(id)即可解决。