Question

我使用进入db的managedBean并使用db data定义bean属性。但是，当我更新db时，我在bean中收到的数据不会更新。

db中的查询是这样的：

    private static final String JPQL_FIND_BY_ID = "SELECT c FROM Category c WHERE c.idcategory=:id";
@Override
public Category findCatById(int id) {
    Query query = em.createQuery(JPQL_FIND_BY_ID, Category.class);
    query.setParameter("id", id);
    Category cat = null;
    try {
        cat = (Category) query.getSingleResult();
    } catch (Exception e) {
        e.printStackTrace();
    }
    return cat;
}

我用来获取类别的托管bean要求ejb在db中进行查找：

@ManagedBean
public class CategoryBean {
    private String idCategoryStr;
    private Category category;
    private int id;

    @EJB
    private CategoryLookUp categoryService;

    @PostConstruct
    public void init() {
        this.category = categoryService.findCatById(id); //id defined in constructor
        System.out.println(this.category.getName());//this will give the same
                                             //name before and after db update
    }

    public CategoryBean() {
        FacesContext fc = FacesContext.getCurrentInstance();
        Map<String, String> paramsMap = fc.getExternalContext()
                .getRequestParameterMap();
        this.idCategoryStr = paramsMap.get("id");
        try {
            id = Integer.parseInt(idCategoryStr);
        } catch (Exception e) {

        }
    }
//get&set
}

如果我更改了我的数据库中的类别标题，即使调用@PostConstruct并且id正确，它在我的bean中也会保持不变。

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.1"
    xmlns="http://xmlns.jcp.org/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/persistence http://xmlns.jcp.org/xml/ns/persistence/persistence_2_1.xsd">
    <persistence-unit name="my-pu" transaction-type="JTA">
    <jta-data-source>jdbc/forumcsDS</jta-data-source>
    <class>main.java.entities.Category</class>
    <class>main.java.entities.Country</class>
    <class>main.java.entities.Forum</class>
    <class>main.java.entities.Message</class>
    <class>main.java.entities.Post</class>
    <class>main.java.entities.Thethread</class>
    <class>main.java.entities.Usercfg</class>
    <class>main.java.entities.Usercredential</class>
    <class>main.java.entities.Userinfo</class>
    <class>main.java.entities.User</class>
    <class>main.java.entities.Friend</class>
    </persistence-unit>
</persistence>

Answer 1

您获得旧值的原因是您的实体存储在二级缓存中。当您第二次请求时，不会执行数据库调用，但会返回内存中的值。

您可以通过将<property name="eclipselink.cache.shared.default" value="false"/>添加到property的{{1}}部分来停用缓存

JPA没有收到更新的数据

1 个答案: