Hibernate 再接触性能优化

Sessionclear

否则session缓存里越来越多

Java有内存泄露吗？

在语法中没有（垃圾自动回收）但是在实际中会有比如读文件没有关什么的

1+N问题

解决方法：把fetch设置为lazy 什么时候就为空

Bachsize 只是缓解

使用joinfetch

Category

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import org.hibernate.annotations.BatchSize;

@Entity

//@BatchSize(size=5)

public class Category {

	private int id;

	private String name;

	@Id

	@GeneratedValue

	public int getId() {

		return id;

	}

	public void setId(int id) {

		this.id = id;

	}

	public String getName() {

		return name;

	}

	public void setName(String name) {

		this.name = name;

	}

}

Msg

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.ManyToOne;

@Entity

public class Msg {

	private int id;

	private String cont;

	private Topic topic;

	@ManyToOne

	public Topic getTopic() {

		return topic;

	}

	public void setTopic(Topic topic) {

		this.topic = topic;

	}

	@Id

	@GeneratedValue

	public int getId() {

		return id;

	}

	public void setId(int id) {

		this.id = id;

	}

	public String getCont() {

		return cont;

	}

	public void setCont(String cont) {

		this.cont = cont;

	}

}

Msginfo

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.ManyToOne;

public class MsgInfo {

	private int id;

	private String cont;

	private String topicName;

	private String categoryName;

	public MsgInfo(int id, String cont, String topicName, String categoryName) {

		super();

		this.id = id;

		this.cont = cont;

		this.topicName = topicName;

		this.categoryName = categoryName;

	}

	public String getTopicName() {

		return topicName;

	}

	public void setTopicName(String topicName) {

		this.topicName = topicName;

	}

	public String getCategoryName() {

		return categoryName;

	}

	public void setCategoryName(String categoryName) {

		this.categoryName = categoryName;

	}

	public int getId() {

		return id;

	}

	public void setId(int id) {

		this.id = id;

	}

	public String getCont() {

		return cont;

	}

	public void setCont(String cont) {

		this.cont = cont;

	}

}

Topic.java

package com.bjsxt.hibernate;

import java.util.ArrayList;

import java.util.Date;

import java.util.List;

import javax.persistence.Entity;

import javax.persistence.FetchType;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.ManyToOne;

import javax.persistence.NamedQueries;

import javax.persistence.NamedQuery;

import javax.persistence.OneToMany;

import org.hibernate.annotations.BatchSize;

@Entity

@NamedQueries(

        {

            @NamedQuery(name="topic.selectCertainTopic", query="from Topic t where t.id = :id")

        }

        )

        /*

@NamedNativeQueries(

        {

            @NamedNativeQuery(name="topic.select2_5Topic", query="select * from topic limit 2, 5")

        }

        )

        */

public class Topic {

    private int id;

    private String title;

    private Category category;

    private Date createDate;

    private List<Msg> msgs = new ArrayList<Msg>();

    @OneToMany(mappedBy="topic")

    public List<Msg> getMsgs() {

        return msgs;

    }

    public void setMsgs(List<Msg> msgs) {

        this.msgs = msgs;

    }

    public Date getCreateDate() {

        return createDate;

    }

    public void setCreateDate(Date createDate) {

        this.createDate = createDate;

    }

    @ManyToOne

    public Category getCategory() {

        return category;

    }

    public void setCategory(Category category) {

        this.category = category;

    }

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getTitle() {

        return title;

    }

    public void setTitle(String title) {

        this.title = title;

    }

}

@Test
public void testSave() {
Session session = sf.openSession();
session.beginTransaction();

for(int i=0; i<10; i++) {
Category c = new Category();
c.setName("c" + i);
Topic t = new Topic();
t.setCategory(c);
t.setTitle("t" + i);
t.setCreateDate(new Date());
session.save(c);
session.save(t);
}

session.getTransaction().commit();
session.close();
}

//N+1
@Test
public void testQuery1() {
Session session = sf.openSession();
session.beginTransaction();
//List<Topic> topics = (List<Topic>)session.createCriteria(Topic.class).list();
List<Topic> topics = (List<Topic>)session.createQuery("from Topic").list();

for(Topic t : topics) {
System.out.println(t.getId() + "-" + t.getTitle());
}
session.getTransaction().commit();
session.close();

}

@Test
public void testQuery2() {
Session session = sf.openSession();
session.beginTransaction();
//List<Topic> topics = (List<Topic>)session.createCriteria(Topic.class).list();
List<Topic> topics = (List<Topic>)session.createQuery("from Topic").list();

for(Topic t : topics) {
System.out.println(t.getId() + "-" + t.getTitle());
System.out.println(t.getCategory().getName());
}
session.getTransaction().commit();
session.close();

}

//@BatchSize
@Test
public void testQuery3() {
Session session = sf.openSession();
session.beginTransaction();
//List<Topic> topics = (List<Topic>)session.createCriteria(Topic.class).list();
List<Topic> topics = (List<Topic>)session.createQuery("from Topic").list();

for(Topic t : topics) {
System.out.println(t.getId() + "-" + t.getTitle());
System.out.println(t.getCategory().getName());
}
session.getTransaction().commit();
session.close();

}
//join fetch
@Test
public void testQuery4() {
Session session = sf.openSession();
session.beginTransaction();
//List<Topic> topics = (List<Topic>)session.createCriteria(Topic.class).list();
List<Topic> topics = (List<Topic>)session.createQuery("from Topic t left join fetch t.category c").list();

for(Topic t : topics) {
System.out.println(t.getId() + "-" + t.getTitle());
System.out.println(t.getCategory().getName());
}
session.getTransaction().commit();
session.close();

}
public static void main(String[] args) {
beforeClass();
}

list是马上取出来而iterator是在用的时候才取不占缓存　　

Category

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import org.hibernate.annotations.BatchSize;

@Entity

//@BatchSize(size=5)

public class Category {

    private int id;

    private String name;

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

}

Msg

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.ManyToOne;

@Entity

public class Msg {

    private int id;

    private String cont;

    private Topic topic;

    @ManyToOne

    public Topic getTopic() {

        return topic;

    }

    public void setTopic(Topic topic) {

        this.topic = topic;

    }

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getCont() {

        return cont;

    }

    public void setCont(String cont) {

        this.cont = cont;

    }

}

Msginfo

package com.bjsxt.hibernate;

import javax.persistence.Entity;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.ManyToOne;

public class MsgInfo {

    private int id;

    private String cont;

    private String topicName;

    private String categoryName;

    public MsgInfo(int id, String cont, String topicName, String categoryName) {

        super();

        this.id = id;

        this.cont = cont;

        this.topicName = topicName;

        this.categoryName = categoryName;

    }

    public String getTopicName() {

        return topicName;

    }

    public void setTopicName(String topicName) {

        this.topicName = topicName;

    }

    public String getCategoryName() {

        return categoryName;

    }

    public void setCategoryName(String categoryName) {

        this.categoryName = categoryName;

    }

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getCont() {

        return cont;

    }

    public void setCont(String cont) {

        this.cont = cont;

    }

}

Topic.java

package com.bjsxt.hibernate;

import java.util.ArrayList;

import java.util.Date;

import java.util.List;

import javax.persistence.Entity;

import javax.persistence.FetchType;

import javax.persistence.GeneratedValue;

import javax.persistence.Id;

import javax.persistence.ManyToOne;

import javax.persistence.NamedQueries;

import javax.persistence.NamedQuery;

import javax.persistence.OneToMany;

import org.hibernate.annotations.BatchSize;

@Entity

@NamedQueries(

        {

            @NamedQuery(name="topic.selectCertainTopic", query="from Topic t where t.id = :id")

        }

        )

        /*

@NamedNativeQueries(

        {

            @NamedNativeQuery(name="topic.select2_5Topic", query="select * from topic limit 2, 5")

        }

        )

        */

public class Topic {

    private int id;

    private String title;

    private Category category;

    private Date createDate;

    private List<Msg> msgs = new ArrayList<Msg>();

    @OneToMany(mappedBy="topic")

    public List<Msg> getMsgs() {

        return msgs;

    }

    public void setMsgs(List<Msg> msgs) {

        this.msgs = msgs;

    }

    public Date getCreateDate() {

        return createDate;

    }

    public void setCreateDate(Date createDate) {

        this.createDate = createDate;

    }

    @ManyToOne

    public Category getCategory() {

        return category;

    }

    public void setCategory(Category category) {

        this.category = category;

    }

    @Id

    @GeneratedValue

    public int getId() {

        return id;

    }

    public void setId(int id) {

        this.id = id;

    }

    public String getTitle() {

        return title;

    }

    public void setTitle(String title) {

        this.title = title;

    }

}

    @Test

    public void testQueryList() {

        Session session = sf.openSession();

        session.beginTransaction();

        //List<Topic> topics = (List<Topic>)session.createCriteria(Topic.class).list();   //发一次select

        List<Category> categories = (List<Category>)session.createQuery("from Category").list();   //找出来 但是不查找

        for(Category c : categories) {

            System.out.println(c.getName());     //用的时候才发select

        }

        List<Category> categories2 = (List<Category>)session.createQuery("from Category").list();  //再一次faselect

        for(Category c : categories2) {

            System.out.println(c.getName());

        }

        session.getTransaction().commit();

        session.close();

    }

    //join fetch

    @Test

    public void testQueryIterate() {

        Session session = sf.openSession();

        session.beginTransaction();

        //List<Topic> topics = (List<Topic>)session.createCriteria(Topic.class).list();

        Iterator<Category> categories = (Iterator<Category>)session.createQuery("from Category").iterate();

        while(categories.hasNext()) {

            Category c = categories.next();

            System.out.println(c.getName());

        }

        Iterator<Category> categories2 = (Iterator<Category>)session.createQuery("from Category").iterate(); //从session缓存里面找

        while(categories2.hasNext()) {

            Category c = categories2.next();

            System.out.println(c.getName());

        }

        session.getTransaction().commit();

        session.close();

    }

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